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  • Question asked 2018-06-30 12:22:47 ... Most recent comment 2018-07-13 20:52:20
    Question

    ​Hello,

    Before I start doing multiple tests maybe someone can steer me in the right direction or even better allready have the solution to theis problem. 

    I need to seal fabric to close the holes in the weaving allowing me to spread magic smooth epoxy on top without it going through.  I need a permanent adherence between the fabric, the sealer and the epoxy. The sealer has to be flexible and permanent. 

    Thanks for your time.

    Best,

    Tao

  • Question asked 2018-06-28 22:45:16 ... Most recent comment 2018-07-01 14:59:35
    Oil Paint Paint Making Pigments Scientific Analysis
    Question

    ​If it is not available, I would like to make a database of the refractive index of Oil Paint samples, along with their partical sizes per a given unit of paint, for each currently available, and respected oil paint manufacturar.

    Is this information which has already been collected? If it is, I would really appreciate information on how to access to the data.

    I am not sure how to catagorize this question.

  • Question asked 2018-06-17 12:13:24 ... Most recent comment 2018-06-29 06:56:07
    Sizes and Adhesives Other Industrial and Non-Traditional Products Art Conservation Topics
    Question

    Would building up layers of texture or mass using things like toilet paper or tissue papers or newspapers covered in acrylic medium or PVA glue be a bad idea from a conservation perspective? The only thing that I managed to find online is that polymer-encasing won't stop paper degradation itself, but I'm wondering if such degradation would be detrimental to the entirety of a work (presuming we only use the paper for structural purposes and don't care if it gets brittle or yellows itself).

    Would it be better to soak the paper and shred it before mixing with a polymer and plaster to make a cellulose clay-like substance?

    I tried searching for information about conservation issues with papier mache related to acidity, but couldn't find anything.

  • Question asked 2018-06-16 16:42:49 ... Most recent comment 2018-06-19 09:08:41
    Question

    ​I am creating a slate-veneer panel for oil painters using flexible slate veneer and aluminum composite material. Here are three photos: 

    https://drive.google.com/open?id=1k1Q9hXYUjTgjybDCTfTHfX-XmYQik_XK

    The back of the slate veneer almost certainly has acidic adhesive to adhere a thin felt backing. (It's building material.) ​So, is it necessary to seal the back of the veneer with something like GAC 100 before adhering it to the substrate, or does adhering it seal it enough? I used Golden Soft Gel to adhere the slate to the ACM, and it worked very well. On the sample in the photos, I sealed the back of the veneer with two coats of GAC-100 before adhering it, but I'd like to skip that step, if the panel would still be satisfactory. 

    Thanks, Amanda Teicher, Seattle

  • Question asked 2018-06-09 04:33:36 ... Most recent comment 2018-06-18 12:16:26
    Question

    ​Hello,

    Recommended practice is to not glue cross braces to the back of a (let us say, 1/4 inch tempered hardboard, or 1/2 to 3/4 inch Medex (minimum formaldehyde MDF panels).  Considering medium large, 36 by 48 inch panels, or similar.

    I assume/ have read that the reason is to minimize or eliminate the bracing  "marks" appearing in the painting over time, and the potential warpage these wood strips may undergo.

    How can the cross bracing perform its intended function of keeping the panel from "cupping" or "bowing", when it is only attached to perimeter bracing?

    Has the website ever considered a "visual database" of contemprary "best practice" supports?  For example, every internet search for building a wood panel for painting recommends glueing cross braces to the back of the panel, which is, probably, bad.  But not doing so  may lead to "warping, bowing, cupping"; also bad.

    Pictures would be helpful.  Thank you for considering questions that are more implicit than explicit, and many thanks for your time and effort considering these issues.

  • Question asked 2018-06-12 19:08:44 ... Most recent comment 2018-06-13 10:25:49
    Drying Oils
    Question

    ​Dear Mitra people

    As a painter I’m very aware of the need to correctly size supports prior to painting in oils on them. I’m now getting back into printmaking and am puzzled as to how the paper copes with oil-based inks such as are used for lino printing. etching etc. I know there are water based inks available. However, I much prefer the oil based ones (and have already bought some). I’m wondering if the papers used for such prints (even the best quality printmaking papers) are doomed to eventual degradation due to the oil in the inks, which can, for example, in a link print, be used in considerable quantity. I do note the survival of many such prints over the centuries, such as Rembrandt’s etchings etc. I’d be very interested to hear your thoughts on this question. 

  • Question asked 2018-06-03 13:37:10 ... Most recent comment 2018-06-09 10:05:58
    Alkyd Grounds / Priming Oil Paint Pigments
    Question

    ​Hello MITRA folks! Can you recommend the best white oil paint (used thinly) for both a straight white Imprimatura and a pale colored Imprimatura? Thin, of course, and non-Zinc. I'm also wondering if a product like Gamblin Ground could be used? Whatever I use needs to be non-yellowing if some areas are left exposed, and also needs to take varnish the same as further layers of oil paint. Hope that's clear. I used to do this with a Zinc-based paint, but apparently that is NOT a viable option anymore. Thanks for your thoughts.

  • Question asked 2018-06-07 09:52:48 ... Most recent comment 2018-06-08 06:51:38
    Egg Tempera Ink
    Question

    ​Does anyone (Dr. Joyce Stoner?) know if Andrew Wyeth always began his egg temperas with an India ink underdrawing, or did he do so only for certain paintings, or for just part of his career (i.e. early on)?  

    Thanks,

    Koo Schadler

  • Question asked 2018-05-25 11:07:44 ... Most recent comment 2018-06-08 03:05:54
    Health and Safety Solvents and Thinners Art Conservation Topics Environment
    Question

    ​Hi all,

    There is a recent thread on the WetCanvas forum discussing the relatively new 'non-toxic' solvent produced by Sennelier under their Green for Oil Range:

    http://www.sennelier-colors.com/en/Green-for-oil_fiche_9895.html

    http://www.sennelier-colors.com/en/Green-for-oil-thinner_fiche_9896.html

    http://www.wetcanvas.com/forums/showthread.php?t=1447854

    They claim that it is non-toxic and apart from the warning that it shouldn't be ingested there doesn't appear to be any warnings online about ventilation or toxicity. I was under the impression that all solvents were toxic to some extent, but if a well known brand can market this product and without any warning information then maybe it is non-toxic?

    There is speculation on the WetCanvas thread that due to it's more oil like feel and very slow evaporation rate that it is likely a 'biodiesel' - a methyl ester of fatty acids. I am not a chemist but if I understand the science correctly: 

    "Biodiesel is produced from linsed oil through a procescaled transesterifcation [12], with this proces the higherfaty acids are separated to methyl and ethyl esters usingmethanol and catalyst KOH.Biodiesel fuel has beter properties than that ofpetroleum diesel fuel such as renewable, biodegradable,non–toxic, and esentialy fre of sulfur and aromatics. Thepurpose of transesterification proces is to lower the viscosityof the oil. The viscosity values of linsed oil methyl andethyl ester highly decreases after the transesterificationproces. The viscosity values of vegetable oils vary betwen 27.2 and 53.6mm2/s, whereas those of vegetable oil methylesters betwen 3.59 and 4.63 mm2"

    So if this is correct it sounds like it is a very low viscosity oil that can be added in small amounts to thin out oil paint.

    I am going to try some out myself, but wondering if anyone hear had any experience with this product or any thoughts on it from a conservation perspective.

    It feels to me that there is a growing concern over the toxicity of solvents and the marketing of non-toxic alternatives, which might still have toxicity or archive issues.

  • Question asked 2018-06-07 03:37:52 ... Most recent comment 2018-06-08 02:47:39
    Pigments Oil Paint
    Question

    Hi all,

    I prefer to use Iron Oxide Black (PBk11) for my darkest values as I read that unmixed Lamp Black (PBk6) can have cracking issues due to the very small pigment size and oil absorbing nature. I use it pure for the darkest values and then mixed in with other pigments for the darker colours in my painting.

    However I do find Iron Oxide Black dries a bit quick. Would mixing it with Lamp Black be acceptable from an archival point of view so I get a bit more open time? Would the Iron Oxide help the paint film withthe larger particles and less oil rich nature?

    I work on rigid panels on a toothy surface with paints made more fluid with walnut oil (no solvents). With this extra oil and lack of movement do you think I would experience any issues with using pure Lamp Black areas? Or would it be safer to use a mix with Iron Oxide Black or Iron Oxide on it's own?

    Thank you,
    Richard

  • Question asked 2018-01-26 12:11:23 ... Most recent comment 2018-06-05 10:36:46
    Rigid Supports
    Question

    Hi, I've sometimes used cradled birch plywood panels for smaller works (from 4"x5" up to 11"x14") over the past 5 years. I size the panels on all surfaces with an acrylic medium (GAC100) and prime the face with 4 coats of acrylic gesso. The brand of panel I use seems to be of good quality. There is no raising of fibers when I size them. However, I've seen some instances of people on painting forums implying that plywood panels will "definitely" crack over time - no exceptions - and shouldn't be used.  How accurate is that assertion in your estimation?   The article at: http://www.justpaint.org/understanding-wood-supports-for-art-a-brief-history/ says " Completely sealing and priming the plywood with several layers of gesso is essential to eliminate future cracking ... "  This implies that, with proper preparation, plywood panels are a viable long term support. Am I correct in that assumption?   

  • Question asked 2018-06-03 15:08:39 ... Most recent comment 2018-06-03 22:19:20
    Rigid Supports Industrial and Non-Traditional Products
    Question

    I have just received a sample of slate veneer, which I believe has the potential to be a terrific surface for oil paintings, especially if some of the slate is left visible in the finished painting. This slate veneer is thin and flexible. You can cut it with scissors, but it's real stone. The sample I have has a thin cotton felt backing. I asked the supplier if he knew if the adhesive used on the back were pH neutral. He didn't know. (Slate veneer is usually used in woodworking.) I'd like to know if there's a way to have this sample tested, so I'll be sure it's OK to adhere to a substrate of aluminum composite material (using either BEVA 371 Film or one of Golden's acrylic mediums). 

    If you're curious to look at the slate veneer, I made a 1-minute YouTube video called "This is Slate Veneer." Here's the link: https://youtu.be/X2NjyON3QOs

    By the way, if I do create an ACM panel with slate veneer, I would seal the surface of the slate with a gloss or semi-gloss acrylic medium (whichever Golden recommends) before painting on it. 

    Thanks for your help.

    Amanda Teicher

  • Question asked 2018-05-30 22:18:37 ... Most recent comment 2018-06-03 14:39:31
    Grounds / Priming Rigid Supports
    Question

    Hello,

    Would you mind sharing your knowledge about copper as a surface for an oil painting? 

    I make artist’s panels for myself and other Seattle artists with aluminum composite material as a substrate. They feature various surfaces. 

    I’ve been researching copper, and I've just learned that, even if it's sealed properly with Incralac, the copper will only stay shiny for about 5 years, according to a technical expert at Talas. I called to ask about Incralac, and he told me that copper isn’t expected to stay shiny indefinitely, that it’s incredibly prone to corrosion. Because of that conversation, I’ve chosen to stop research and development on copper-veneer panels. I am now reluctant to develop a copper-veneer panel without more assurance from experts that there is a way to preserve its shine that would satisfy artists, conservators, and collectors.

    What do you think? 

    Thanks so much for your time and expertise. 

    Amanda T.

    Seattle

  • Question asked 2018-05-13 01:14:12 ... Most recent comment 2018-05-31 23:16:13
    Art Conservation Topics Oil Paint Solvents and Thinners
    Question

    I was curious if using amylase powder - available in large amounts, as people use it to convert starch to sugar - can be used to create a more effective cleaning solution for a large area, rather than having to drink water and spit all over an oilpainting's surface?

    Amylase powder it's suposedly the key enzyme in spit that cleans things, so I figured why not create a large batch for a giant surface, rather than having to worry about what I eat or stay hydrated?  "cause sometimes I just want to eat garlic y'know?

  • Question asked 2018-05-28 15:34:50 ... Most recent comment 2018-05-31 14:44:22
    Studio Tools and Tips
    Question

    ​Hi,

    First of all, please forgive my poor English! I work sitting in front of a desk. I use acrylic paints on rigid supports. My pieces are not put horizontally on the desk but slightly leaning. I have just seen a photo of Alex Colville's standing desk and am wondering whether some of you work in a standing position with a table easel. If yes, do you know where to buy one? Or if I need to build it myself, would you have some advice about what it should be like?

    Thanks!

  • Question asked 2018-05-17 10:04:50 ... Most recent comment 2018-05-30 19:11:01
    Egg Tempera
    Question

    Hi Brian,

     

    In a reply to a recent post you said, "…works painted over earlier compositions are much more likely to develop delamination issues over time." This raised questions for me.

     

    1.  Why is this so? Is it because newly formed oil paint films don't crosslink with dried paint underneath?  How much less absorbent is a dried oil paint film versus acrylic gesso ground?  And were you referring to oil paint only, or other mediums?

     

    2.  Would you say the same is true for egg tempera; that delamination is more likely to occur in works painted over earlier compositions?

     

    3. The case is often made that dispersive adhesion is primary; however in my experience with egg tempera mechanical adhesion seems equally important.  When I've continued painting on aged egg temperas (from a few weeks to over a year old; i.e. partially or fully polymerized surfaces) the paint is more difficult to work with; much more prone to lifting if I do things like sponge on watery paint, or lightly sand or polish as I develop layers.  This seems to indicate less than ideal adhesion between old and new egg tempera paint layers; and that they "are much more likely to develop delamination issues over time".  And yet I've also been told (by well-informed people) that it's fine to paint atop old, polymerized egg tempera with fresh tempera (as long as the surface is clean).   Your thoughts?  

     

    4.  To address the less than ideal working properties of fresh tempera paint applied to a polymerized surface, I do three things to the surface: 1. Wipe off dust, 2. Do a gentle sanding with a 1500-grit sanding pad, to open the surface, 3. Apply a very thin nourishing layer of egg yolk medium (1 part yolk to maybe 8 parts water).  I'm actually not quite sure why I do #3, except that it seems to help the paint grip and behave better – but I also wonder if the nourishing layer is more detrimental (i.e. contributes toward fatty acid migration, or even delamination) than helpful.  Again, your thoughts?

    Thanks as always!

     

    Koo 

  • Question asked 2018-05-10 01:26:17 ... Most recent comment 2018-05-30 01:33:10
    Technical Art History
    Question

    ​Just curious, in regards to the writings of eastlake what are some of the technical inaccuracies promoted by him? What would be the benefit of reading his work? I know he talks a lot about the Flemish painters, do you know of any other resource that would give solid information not only on the practices of certain painters from the northern renaissance (like van eyck) but also materials? Thanks!


    Regards,

    Justas

  • Question asked 2018-05-28 20:42:04 ... Most recent comment 2018-05-29 07:23:25
    Flexible Supports Grounds / Priming Oil Paint
    Question

    ​Hi! I guess this is a topic already answered, but I coudn't find it.
    I've read both that the reverse of the canvas shouldn't be sized/primed and also that the current thread between conservators said that should be sized (and then mounted in a more rigid support). Well, should the back of the canvas, the raw linen, be sized and primed or not?

  • Question asked 2018-04-11 04:16:42 ... Most recent comment 2018-05-26 06:46:23
    Photo-Documentation / Digital Printing Industrial and Non-Traditional Products
    Question

    ​I am looking to print on acetate/transparencies - are these compatible to overlay over lithographs to make fine art collages/assemblages?  I am unsure whether commerical transparencies are archival/acid free.  Grafix are the only company which appear to state their acetates are acid-free/printer friendly for fine art use but I am limited by their sizes.  I am using an inkjet printer.  Are these methods archival once framed behind UV glass? (Based in UK) Are there other alternatives for using transparent overlays which can be digitally printed on?

  • Question asked 2018-05-22 13:06:13 ... Most recent comment 2018-05-23 18:28:54
    Oil Paint Drying Oils
    Question

    What kind of mediums or additives​ can I add to my oil paint to give it a sticky/stringy quality that won't also cause the paint to level? The use of bodied oils provides the stickyness and stringiness, but levels too much. 

  • Question asked 2018-05-12 18:04:33 ... Most recent comment 2018-05-14 21:49:51
    Oil Paint
    Question

    ​I have been doing small studies from life on Arches Oil Paper that have had 3 coats of acrylic gesso applied.  I realize the oil paper does not need the acrylic ground applied, but I prefer the surface prepared in this way. 

    I would like to mount or otherwise prepare a 6"x8" oil study as a gift to a family member.  What would be the best method?  I don't expect the painting to last for centuries, but hope to get at least a few good years of enjoyment out of the painting.  I work in sizes up to about 9"x12" on Arches Oil paper with the acrylic ground, so if you can address any issues going up to this size as well, just in case any future studies might be given as a gift, that would be appreciated. For my more serious work that I hope lasts a long time, I paint on tempered hardboard prepared with acrylic ground, but cost and storage space prevent me from always working on hardboard, especially when most of the studies are for my personal learning experience.  

    The other option would be for me to paint studies on hardboard and repaint over unsuccessful paintings.  Would this be a sound practice assuming the paintings have not been varnished?  Any advice on this practice?

    Thank you to all who contribute their time to this forum, it is very much appreciated.

    Thanks in advance. Barbara

  • Question asked 2018-04-27 11:19:02 ... Most recent comment 2018-05-13 13:35:10
    Flexible Supports
    Question

    ​Looking for plain weave umprimed linen canvas 8x8 warp and weft, who makes or carries a linen canvas like this? 

  • Question asked 2018-05-10 15:00:04 ... Most recent comment 2018-05-10 15:16:22
    Health and Safety
    Question

    ​This may be redundant, I didn’t see too much on it here though.  My question is about waste management. I’m an oil painter, so paint including lead white, and mineral spirits are my concerns. I have not painted for about two years because I am a hypochondriac, and my current studio space is a basement apartment. I am trying to get over it, and have been trying to find some clarity. I live in Utah, and I actually contacted my state office of solid and hazardous waste, and explained what I was doing, the waste I was generating and an estimate at the quantity. They  indicated to me that even though I was engaged in activities for profit, my residential status and volume would allow disposal into the municipal waste stream. I also contacted my local transfer station, and they will accept up to 5 gallons of waste at a time for 8$, which is very reasonable. My problem is safe storage. In a day, I might generate 3 or 4 paper towels with a few milliliters worth of paint, and some mineral spirits stained areas. For final brush cleaning I will use two small bowls of water and wipe the waste out on a paper towel so as not to have it go down the drain.  I am storing these materials for a week or two in a justrite oily waste can until I take it to the transfer station, how safe is this given my living environment? Does solvent evaporate out of those cans? Am I trapping volatile compounds and releasing them every time I open it? The can says empty every night which makes no sense. I am not opposed to “solvent free” however large quantities of drying or vegetable oil on rags still present a combustion risk. And varnishing procedures are not accomplished without use of solvent. So I can’t entirely get away from solvent. I am also curious what artists were doing with waste throughout history. There were thousands of artists working in Paris in th 19th century. Where did all their painting rags go? Anyway I apologize for my neurosis I just want to keep working, but my anxiety makes me think that I’m storing waste that will explode into flames at any moment.                                                                                 

  • Question asked 2018-04-21 13:35:10 ... Most recent comment 2018-05-10 09:48:28
    Rigid Supports Flexible Supports Scientific Analysis
    Question

    ​I like many am interested in the materials used by my favorite past masters. As conservators, are there any current manufacturers that would supply a linen texture that is close to what an artist like John Singer Sargent might use? Does that knowledge enter the realm of conservation needs? If anyone is also familiar with trends in support texture for artists who painted thickly like sargent, sorolla, zorn, etc. that would be excellent as well. 

  • Question asked 2018-05-02 18:56:34 ... Most recent comment 2018-05-03 03:46:51
    Pigments Oil Paint Art Conservation Topics
    Question

    ​Cassel Earth, NB8, bituminous earth.

    A pigment I have long been contemplating on using although I have only used imitations of this pigment(premixes to replicate it),I have read a few things on this pigment and know that it is not stable at all and that there have been quite a few paintings from history that have suffered from its usage but also that it was used successfully in some.However there are paint manufacturers who produce this pigment.Should this be avoided or is there a way to safely handle this pigment?

    R.

  • Question asked 2018-05-01 00:00:05 ... Most recent comment 2018-05-02 19:25:23
    Oil Paint Health and Safety
    Question

    Dear Mitra :

    I was having a discussion with an artist who often sleeps in her studio. It's a small space, without good ventilation, so she paints solvent-free. She works on two or three paintings at a time and hangs them on the walls to dry. She's fairly sure that sleeping in the studio is fine. I wonder about that ( many of us have had to "work where we live" at some point in our lives ).  The only information I could find about solvent-free linseed-oil paint and aldehydes, etc., dealt with house paint. 

        Is sleeping in the studio - or for that matter, hanging wet paintings in the bedroom - really a safe practice, even if you don't use solvent?

  • Question asked 2018-04-27 11:24:04 ... Most recent comment 2018-05-01 23:22:26
    Art Conservation Topics Oil Paint Casein Paint Making Pigments Technical Art History
    Question

    ​I would like to find out what is the best way to prepare cochineal to last as much as possible, (is there anything that can be done to improve its lighfastnest) 

  • Question asked 2018-04-27 04:01:23 ... Most recent comment 2018-05-01 02:14:36
    Acrylic Varnishes
    Question

    Hi all,

    I have an acrylic painting on a smooth panel. I would like to try to retain the brush strokes and smoothness when I apply an isolation coat and varnish. For the varnish I can always use a spray, but for the isolation coat I'm a bit stuck without having access and experience of an airbrush.

    Is there any product that applies an acrylic resin in a spray form that would serve as an isolation coat? Would a non-removable varnish work if I then used a removable varnish for the 'varnish' layer?

    Any suggestions would be gratefully received! :)

    Richard

  • Question asked 2018-04-30 18:27:15 ... Most recent comment 2018-04-30 21:01:41
    Acrylic Gilding
    Question

    Is it sound to use acrylic medium instead of the regular gilding paste to attach imitation goldleaf to a rigid, gessoed support? Is it fine to put acrylic on top of said gilding? Would there be any archival problems with such a solution?​

  • Question asked 2018-04-24 11:23:00 ... Most recent comment 2018-04-24 22:30:12
    Rigid Supports Sizes and Adhesives
    Question

    ​I have decided to make custom 48" x 72" single-layer wood panels.  I plan to use a 1/4" plywood or MDF panel over a 2" plywood cradle with cross struts every 24" with corner bracing.  Is there an archival preference for plywood or MDF?  Could you would recommend a wood variety or brand of MFD?  Are plywood cradle struts better than a solid wood cradle, such as poplar?  I will apply two (2) coats of Acrylic Gel Medium.  I will then apply 1/4" to 1/2" of textured modeling paste before I apply acrylic paints.  Are there any issues I should consider with very thick modeling paste, such a reinforcement? thanks

  • Question asked 2018-04-04 00:24:09 ... Most recent comment 2018-04-23 19:18:45
    Oil Paint Studio Tools and Tips
    Question

    Dear MITRA,

    I love sable oil painting brushes but am looking for a animal-friendly alternative. Can anyone reccomend a high quality synthetic sable brush that handles similarly to the real thing?

    Thanks!
  • Question asked 2018-04-16 19:33:46 ... Most recent comment 2018-04-21 19:20:53
    Oil Paint Acrylic Watercolor Pigments
    Question

    ​Hi, I was wondering if any of the Moderators have had a chance to try this relatively new colour and if so, what they thought of its usefulness on the artists palette (current exhorbitant cost aside)?

  • Question asked 2018-04-11 20:05:35 ... Most recent comment 2018-04-17 13:39:30
    Acrylic Alkyd Egg Tempera Environment Rigid Supports
    Question

    Hi, 

    Either pigmented shellac or a solvent-based, alkyd house paint (from the hardware store) were recommended to me as good barrier coatings to apply to the back of wood-based panels to protect them from humidity.   A few questions: 

    - Would acrylic paint work as well as alkyd house paint to seal out moisture?  Would it make a difference whether it was an artist grade acrylic paint versus acrylic housepaint?

    - Is a solvent-based, alkyd paint recommended because it seals from moisture more thoroughly than acrylic paint?  Or does the alkyd not necessarily seal better, it's just more durable?

    Thanks,

    Koo

  • Question asked 2018-04-17 00:23:13 ... Most recent comment 2018-04-17 10:00:31
    Animal Glue Flexible Supports Rigid Supports
    Question

    ​Hello,

    Is it possible to safely mount a finished painting on linen (Rabbit skin glue, Lead oil ground) onto a rigid support in order to avoid potential problems caused by the hydroscopic properties of the glue? If so, how can this be done?

    Thank you!

  • Question asked 2018-04-14 06:56:30 ... Most recent comment 2018-04-16 16:40:35
    Question

    ​Can you please explain precisely what "Turpenoid" is, and how it should and shouldn't be used in painting?  


    Thanks,


    Koo

  • Question asked 2018-04-16 00:08:08 ... Most recent comment 2018-04-16 14:06:45
    Rigid Supports Flexible Supports
    Question

    I would like some advice on how to make an archival painting on a 48" x 48" x 2" two-layer hardboard or canvas support.  I plan to cut a symbol thru the top layer and fill the void back 1" to a back layer. 

    In the 2" framed canvas, I plan to polyurethane glue 1" thick Expanded Polystyrene Sheet (EPS) foam to the back of the canvas.  I would then cut the symbol thru the canvas and EPS.  I plan to polyurethane glue & SSTL staple a tempered hardboard backer to the back of the EPS.  Looking at the front of the canvas, you would see the canvas with cut-out symbol and hardboard backer. 

    In the hardboard support, the look would be the same, but the procedure would be the opposite.  I would polyurethane/staple a ¾" cradled hardboard surrounded by 2" plywood frame.  I would then polyurethane glue the 1" EPS foam and inset into the 1" cavity between the hardboard flush to the top edge of the 2" frame.  I would then cut out the symbol and polyurethane/staple the hardboard top to the 2" frame and over the EPS.  I would then wire-cut the EPS foam following the edge of the symbol down to the back hardboard and remove the EPS.  Looking at the front of the hardboard support, you would see the hardboard with cut-out symbol and hardboard backer. 

    I would prefer the canvas support, primarily for weight which would be about 32 lbs. over the hardboard support which could be about 50 lbs.  I would follow the best practices for sealing/priming all surfaces prior to applying acrylic paints.  They both present archival issues and need further development and testing.  I have seen canvas cut thru without back support and know that this will be future archival nightmare.

    Thank you for your advice.

  • Question asked 2018-04-15 14:35:32 ... Most recent comment 2018-04-16 13:56:49
    Oil Paint
    Question

    ​I have a  question regarding Alla Prima work in oil painting.

    Alla Prima is painting all at once, in one session.  However, if I take a break and come back and the paint on the panel is still wet (meaning comes off my finger like it is fresh, not tacky), can I paint into it or will this cause problems?  I am using M. Graham walnut oil paints which seem to be slow drying, unless I am using a lot of burnt umber (for example).  I am going to be working on a portrait that I expect will take 2-3 days working on and off during the day.  Is this okay, or do I need to wait for layers to dry before adding more paint to a section that has previously been painted?  I am not planning on glazing per se. I am using a limited palette of ivory black, titanium white, yellow ochre and cadmium red light.  My exerpience using these colors during life painting alla prima sessions is that the paint does take several days to be touch dry. I recently started mixing my M. Graham titanium/zinc white 50% with Wiliamsburg pure titanium white to cut the amount of zinc, and also to add a bit of linseed to the mix.  I haven't worked a lot with this mix yet and not sure how fast it will dry, but plan on using this mix in the portrait.

    Thanks.

  • Question asked 2018-04-04 13:13:45 ... Most recent comment 2018-04-16 13:21:37
    Alkyd Drying Oils Paint Mediums Oil Paint
    Question

    When painting in oils, it is necessary to avoid putting layers of "lean" (faster-drying) paint over "fat" (slower-drying) paint.​ However, I'm not quite sure how this relates to using alkyd mediums with regular oil paints. The problem is that alkyds dry faster than oils, even though the mediums themselves contain drying oils as well. Therefore, it would seem that layers containing more medium (drying faster) should be painted before the layers containing less medium (drying slower), which is the opposite of using regular linseed or walnut oil in traditional oil painting. Is this correct? Or does it not matter, so long as the previous layer is touch dry (since the solvents in the medium would "bite into" the previous layer)? Also, I remember reading that if alkyd mediums are used, they should be used throughout, in all layers. Is that so?

  • Question asked 2018-04-11 12:22:55 ... Most recent comment 2018-04-11 15:48:01
    Art Conservation Topics Industrial and Non-Traditional Products Other Sizes and Adhesives
    Question

    When working on various supports (paper, board, etc.), it's often convenient to use masking tape in order to produce sharp edges or just keep the work in place. However, I'm not sur​e whether this could have a negative effect on the supports. Most producers of masking tapes don't say anything about their content, and there's no concrete information I could find on the subject online.

    If I use tape during painting/drawing and remove it afterwards, what are the chances that enough substances could migrate from it onto the support to cause issues in the future? For example, would enough of acidic adhesives migrate onto the surface of paper to cause it to degrade or accelerate its degradation in the future?

  • Question asked 2018-03-27 11:24:41 ... Most recent comment 2018-04-11 13:10:45
    Question

    ​Are there any archival quality/acid free polyester (acetate) films suitable for use with inkjet printers?  Images printed on these will then be used as overlays over lithographs on acid free paper.  Is this assemblage process compatible - would it be best to fix the lithograph with a protective spray?  Grafix claim their acetate printable sheets are acid free - but they only produce A4 sheets for craft purposes.  There seems to be mixed data on the archival properties of acetate as it is not a common method for fine art use.

  • Question asked 2018-04-09 21:48:39 ... Most recent comment 2018-04-10 21:06:21
    Grounds / Priming Oil Paint Flexible Supports
    Question

    I would like to start using linen and prime my own canvas. I have a frame commercially made, with pre-stretched duck cotton canvas covered with acrylic ground and I would like to reuse the stretcher. What would be recommended as best practice? to stretch and size the linen over the commercial frame, or take off and toss the cotton canvas and just stretch and size the linen with rabbit skin glue following a traditional method?

    so my question is, streching linen over an existing cotton canvas would help or hinder the longevity?

  • Question asked 2018-04-06 14:42:52 ... Most recent comment 2018-04-09 12:57:28
    Oil Paint Alkyd Paint Making
    Question

    Good Morning.

    In 2005 I painted an oil painting on a wood panel, work that I did not finish. Now in 2018I would like to finish that paint (unfinished).

    I have read on the internet that it is not advisable to paint an old painting (in this case of the year 2005), for a subject of adhesion of the layers.

     

    From the point of view of good practices and good conservation, is there No problem painting that panel(unfinished) after 13 years?

    In the case that there is no problem in painting it, before painting it, I have to add some product so that there is good adhesion between layers (medium, oil, varnish, etc.)?. What should I do before painting?.

     

    This painting is on linen support stuck to wood, board. The support was primed with Gesso acrylic. I painted it years ago with white alkyd titanium Winsor & Newton Griffin brand, The only alkyd color that was used was titanium white, the other colors that were used were oil colors (Winsor Newton Artist). The Also use medium for oil made with turpentine, linseed oil, and shiny varnish.

     

    In relation to the above, and with the rule rule fat over lean:

    Is it possible, advisable (from the point of view of good

    conservation) to paint a panel using the lower layer Quick Drying

    Titanium White Alkyd resin Winsor & Newton Griffin, and in the upper layer use oil paint Lead white (PW1 basic lead carbonate)?.  (I started painting with titanium white alkyd, and after thirteen years, I want to finish the painting with lead white oil paint).

     

    I await your recommendations urgently.

    Thanks.

     

    Regards.

    Cristian A. (artist).

     

  • Question asked 2018-04-08 09:02:58 ... Most recent comment 2018-04-08 11:53:58
    Grounds / Priming
    Question

    ​When I was in college in the 1980's I did course on materials and were taught a recipe to make a primer called a half oil ground. It followed the same recipe as a tradirional gesso ground; rabbit skin glue, calcium carbonate, titanium white only we added half the volume with boiled linseed oil and a egg yolk to help emulsify the mixture. 

    Is this a safe recipe to use? I remember enjoying painting on it.

    Thanks Steven Lewis

  • Question asked 2018-04-04 00:01:56 ... Most recent comment 2018-04-04 16:58:31
    Health and Safety Oil Paint Solvents and Thinners
    Question

    ​Dear MITRA,

    After scraping down my glass palette I have been using rubbing alcohol on a paper towel to clean it. Are there any chemical interactions here that would be unsafe to breath or any residue on the palette that would cause painting problems? It seems to be working great but I want to make sure I'm not doing anything unsafe. I try to minimize my Gamsol use as much as possible because I'm concerned about the potential health problems it can cause.

    I also occassionally use baby wipes to clean off my pallette, which work shockingly well, but they have a fiberous texture that I've found creates more dust (which ends up in my paintings) than regular paper towls. 

    Could rubbing alcohol or other types of alcohol be used as a solvent to clean brushes (like one does with a jar of Gamsol) or as a paint thinner in oil paintings themselves? I had been using Spike Lavendar as a medium for a while with happy results, but learned from MITRA that it's actually not proven to be any safer than Gamsol. 

    Any insight into the use of alcohols in oil painting and cleanup would be much appreciated!

    Thank you!

  • Question asked 2018-02-02 16:51:49 ... Most recent comment 2018-04-04 00:16:14
    Oil Paint Studio Tools and Tips
    Question

    ​I don't think this question has been discussed here? Can anyone suggest a good studio practice to lessen exposure to dust on drying oil paintings? (Not newly-varnished paintings, but during the painting of multiple layers of oil paint.) I've seen cloth draped over paintings in movies, but not sure if that was just for theatrical effect...and how would one keep the cloth from sticking to wet paint anyway...?

  • Question asked 2018-03-31 21:27:03 ... Most recent comment 2018-04-01 21:09:24
    Flexible Supports Acrylic Animal Glue Art Conservation Topics Grounds / Priming
    Question

    ​Hello everyone, great forum :)
    I'm a student painter and nerd for art craft and science. As first question I wanted to ask about industrial canvases: what are the best according to your experience and what kind of materials have been used to be made? Do you trust some brands more than others? What kind of industrial pre primed canvas is the best in terms of durability?

    I'm curious about this because I've been told that some of the best industrial canvases are still seized with some sort of rabbit skin glue prior the white priming, is that true?

  • Question asked 2018-03-29 19:56:43 ... Most recent comment 2018-03-30 00:09:18
    Question

    ​Dear Mitra staff

    I have been experimenting with egg-oil emulsion mediums to add to oil paint (not as paint vehicles as such) and recently saw a reference to “gum tempera emulsion” (medium or vehicle) in Ralph Mayer’s Artist’s Handbook p.278. I was excited by this as I’d rather use a “vegan” emulsion medium if at all possible. The recipe is as follows: 5 parts gum (Arabic) solution; 1 part Stand oil; I part Damar varnish and 3/4 part glycerine. I’ve tried this on clay bird and it seems to be working OK. However I recently read a comment by one of your staff to the effect that gum Arabic is not a natural emulsifier. Does this mean this recipe is actually not really sound and that I should stick with egg oil emulsion mediums? I just want to reiterate that I’ll be using the mixture as a medium with commercial oil paints. I’m not trying to make my own paints. Kind regards, Jenny

  • Question asked 2017-11-28 01:27:08 ... Most recent comment 2018-03-29 23:16:57
    Oil Paint Drying Oils Paint Mediums
    Question

    ​Someone just stated in the "Painting Best Practices" facebook group that coldpressed linseed oil is mechanically superior to alkali refined linseed.
    Is there any truth to this?

    I'm not taking about yellowing, but film strength, flexibility and adhesiveness. (Maybe longevity too.)
    Have there been any studies about this?

  • Question asked 2018-03-15 13:20:14 ... Most recent comment 2018-03-28 21:50:55
    Casein Oil Paint
    Question

    ​I now know that it's not advisable to dilute oil paints with odorless mineral spirits or other solvents for a washy underpainting, as there may be problems with binding (among other issues). Some folks advocate just painting from the tube without solvents, and scrubbing the paints around, but I enjoy the fluidity of a more liquid underpainting.

    I've become interested in casein as an underpainting, and recently purchased and watched James Gurney's "Casein Painting in the Wild" video available from his wonderful blog, http://gurneyjourney.blogspot.com.  I noticed that with his casein plein air paintings, he starts out with a very watered down wash of casein mixed with water and then builds up with more opaque layers of casein. I'm wondering whether this very watery casein underpainting in itself (without the layers of opaque casein), painted on an panel primed with acrylic "gesso" would have sufficient binding power (both to the acrylic gesso and to subsequent layers of oil paint). 

  • Question asked 2018-03-26 09:43:45 ... Most recent comment 2018-03-27 11:28:58
    Flexible Supports Drawing Materials
    Question

    I have a large drawing which has a crease in it.  It is a charcoal drawing on Stonehenge.  The crease is in an area of white, which has no charcoal.  I'm looking for advice on how to repair or minimize the crease, without damaging the drawing.​

  • Question asked 2018-03-21 11:11:08 ... Most recent comment 2018-03-26 07:50:58
    Egg Tempera
    Question

    ​Hello Moderators,

    Last week there was an Egg Tempera Conference in Munich ("Tempera Painting Betwen 1800 and 1950").  Did any of you attend and, if so, can you report on any interesting findings or revelations?

    Thanks,

    Koo Schadler

  • Question asked 2018-03-21 17:28:03 ... Most recent comment 2018-03-22 12:19:39
    Question

    Dear:

    It is easy to find information on the internet about scientific research carried out on works by painters known as Van Gogh and Matisse. Cadmium yellow oil paint is undergoing chemical changes, turning the yellow paint into a pale compound, even changing the consistency of the paint in a salt. This seems to be concerns on the part of museums that see their capital degrade in a short time.

    In the Just Paint article "Will Cadmium Always Be On The Palette? You mention it already:

    "The difference between indoor and outdoor performance is thought to be due to the combination of environmental factors encountered outside; moisture, ultraviolet radiation and air. These cause bleaching induced by oxidation of the cadmium sulfide to cadmium sulfate. That is why the water permeable acrylic vehicle is prone to this effect, while cadmium pigments used in waterproof binders, such as rigid plastics, are not. "

    Without delving into more details as each person can on the internet find expanded information on this matter and the reasons for my query, I raise my concerns.

    1) What difference can there be between the pigments and the oil paints used in those art works and those that are commercialized today? PY 35 Cadmium Zinc Sulphide; and PY35: 1 with Barium according to the source. http://www.artiscreation.com.

    In addition, I have not found any clarification on whether this unexpected effect of cadmium yellow, is also affecting the PY37, PO20, PR108.

    2) Most artists are concerned about the permanence of their works, looking for materials and processes that allow their work to endure. From choosing the substrate, its preparation, the pigments resistant to light, etc. Why then, when mention is made of cadmium yellow, it is practically considered the best option because it is Highly lightfast, ... without taking into account that in a relatively short time it will be chemically transformed into something else.

    3) Regarding the paint manufacturers that include it in their color charts (all), no information or warning about this problem is found and they always assign it the best permanence. Yes, best lightfast, but possibly chemically unstable, reacting with the atmosphere to become a salt.

    In oil paint, the oil will not completely isolate the pigment from atmospheric factors, it will be less exposed than other paints, but even so light, air and environmental humidity will affect.

    For some time I have adopted the Py74 as my yellow, and PY65 as its dark version. 

    I take this place to turn my concern, for being a serious space and with professional people who care and occupy in these issues of art materials.

    Congratulations for the work you do.

    Best regards.

    PD. My native language is Spanish.

     

  • Question asked 2017-05-14 17:00:13 ... Most recent comment 2018-03-22 10:59:01
    Drawing Materials Grounds / Priming Egg Tempera
    Question

    I sometime expose my metal point drawings to sulphur (by placing them under a "tent" alongside an open jar of liver of sulphur) to speed up the oxidation and darkening of the drawing.  Does exposure to sulphur cause any detrimental affects to the materials of a metalpoint drawing (to either a paper or wood-based panel support; or to an acrylic or traditional gesso ground)?  Are there other recommended ways to speed up oxidation?  I had a cohort once tell me he sips whiskey while drawing and blows on his images - any truth to his claim that this speeds oxidation?  

    By the way, which is correct: metalpoint?

    Koo Schadler

  • Question asked 2018-03-18 12:52:13 ... Most recent comment 2018-03-19 10:16:26
    Oil Paint
    Question

    ​I just had the horrible news that a painting I did 12 years ago has started to crack. This is what I can tell you about my process with this painting. I stretched unprimed linen then used some PVA size (tho maybe not enough because you can see white seeping though on the back) and oil primed it using oil ground. I then did an open grisaille using raw umber and burnt sienna and mineral spirits. I then glazed about 4 passes on the painting. I have always felt I obeyed the fat over lean rule, but sometimes in the heat of paintings one can skew up. Though I'm sure I didn't add mineral sprits after the grisaille and I'm sure I used medium, to some degree, each time . I don't know which medium I used. It could have been liquin or a linseed oil, stand oil, mineral spirits mix. I'm wondering if maybe the culprit could be the W/N Paynes Grey I used as it is so slow to dry. At that time I may have been using zinc , I'm not sure when I learned about the evils of zinc. Although from where the cracks are it doesn't seem like I would have used zinc white, I'm also not sure what I used for a varnish, tho I don't think that would be the cause. Any ideas? I'm have nightmares over my paintings now.IMG_2132.JPG

  • Question asked 2018-03-10 13:41:23 ... Most recent comment 2018-03-12 22:17:18
    Casein
    Question

    Per the Richeson site, to make your own casein paints with your favorite pigments: "Mix Shiva Casein Emulsion with powdered pigments: Spray some water on your palette and scoop out the pigment with a palette knife. Mix thoroughly into a paste and add a few drops of Shiva Casein Emulsion. Mix again, and you're ready to paint."  http://www.richesonart.com/products/paints/richesoncasein/richcaseinfaq.html

    I'm wondering if, instead of mixing the casein emulsion with powdered pigments (which I don't have on hand), I can mix it with the array of tubed watercolors in my favorite pigments.  These tubed watercolors obviously contain other things besides pure pigment, such as gum arabic and glycol.

  • Question asked 2018-03-12 15:54:28 ... Most recent comment 2018-03-12 22:00:39
    Alkyd Oil Paint Paint Mediums
    Question

    ​Hello MITRA folks. My question is about the use of oil painting mediums that speed drying time, i.e. alkyd mediums. Does proceeding with each next layer when the previous layer is just "touch dry" (and all layers are relatively thin) mean that, essentially, the painting layers will all be drying at the same time, similar to an Alla Prima approach, and there will little likelihood of crazing, cracking or wrinkling in the topmost layer later on? I see oil painters who use Galkyd and similar mediums in many, many layers in relatively quick succession, and always wonder about drying and curing hazards... Thank you for your thoughts.

  • Question asked 2018-03-09 14:17:46 ... Most recent comment 2018-03-12 06:20:25
    Pigments Scientific Analysis Oil Paint
    Question

    ​Hi all,

    I've emailed several art manufacturers that I use here in the UK regarding the amount of zinc in their titanium white oil paint.

    Here are the results which may prove useful to you all:

    CompanyProportion of Zinc
    Winsor & Newton - Artist Oils"There is not enough to cause a brittle film--less than 2%."
    Royal Talens - Rembrandt"The percentage of zinc oxide for both products is between 5% and 10% … They both contain the same amount of Zinc. The Safflower oil makes sure it’s getting less yellow."
    Schminke - Norma"we can say that our #11114 titanium white have a content of PW4 lower than 10%."
    M Graham - Oil Color"I have been told that we use under 3% Zinc in our Titanium. We do have a zinc free oil 11-181 that I can recommend if there is a concern."
    Jacksons - Artist and Professional Oil RangeWon't reply after 2 mails
    Blockx"Paint made with Titanium Dioxide pigment is very hard and misses elasticity. So, we do add indeed a very little Zinc pigment. But the proportion is of course secret. And will defer from one manufacturer to another. " - Won't reply after 2 more chasing emails
    M Harding"It's about 10% of the overall volume."
    Williamsburg"We are happy to report that we do not use any zinc in our Titanium White oil paint." - 0%
    SennelierWon't reply after 2 mails
    Maimeri - ClassicoWe can declare that the proportion of Zinc in Classico Titanium White 018 is moreless 50%."


  • Question asked 2018-03-09 14:49:12 ... Most recent comment 2018-03-12 06:04:24
    Oil Paint
    Question

    Hi, I work in an istitution that provides art education. They wish to ban oil paints because they believe it to be toxic.

    Is there some facts or arguments I can provide them to dispell their belief?

    Thank You

    Steven Lewis

  • Question asked 2018-02-08 16:53:46 ... Most recent comment 2018-03-09 09:54:24
    Acrylic Oil Paint Industrial and Non-Traditional Products
    Question
    While preparing MDF boards, I used two coats of acrylic enamel paint on the back and around the edges to provide some moisture protection. However, a small amount accidentally ended up on the very edges on the front side of the boards. Assuming I cover the front with three layers of acrylic dispersion ground, should I expect future failures of paint? I know house and commercial paints are generally not formulated with archival qualities in mind, but I was wondering if having them in the bottom-most layers would affect subsequent layers of artist-quality acrylics and oils?

  • Question asked 2018-03-06 23:26:04 ... Most recent comment 2018-03-08 20:37:26
    Oil Paint
    Question

    ​I'd like to hear the opinions of the experts on this linseed oil developed by the University of Saskatchewan.  It sounds great, but I'm not sure if the peptides are necessary for long term for stability of paint films. The news release is here:

     https://news.usask.ca/media-release-pages/2017/u-of-s-basic-research-leads-to-non-yellowing-flax-based-oil-for-artists-paints.php

  • Question asked 2018-02-19 20:26:42 ... Most recent comment 2018-03-06 11:33:28
    Oil Paint Grounds / Priming
    Question

    ​I am interested in building an archivally sound painting. I have been told that a lead based ground will strengthen the oil paint all the way through the paint surface, and therefore is the most archivally sound way to build a painting. I would prefer to build it in other ways and am wondering if I can be effective in matching the performance of lead. Here are my methods: A rigid, cradled panel support behind an evenly stretched 16 oz tightly woven canvas, or a high grade linen, Gamblin PVA sizing, front and back of the fabric, Golden Acrylic Gesso, five coats (slightly diluted), underpaintings in undiluted Gamblin FastMatte Alkyd Safflower oil paints, a series glazes of Gamblin FastMatte paints, diuted to glaze consistance with Gamblin Solvent Free Fluid and applied with high paint spread.

  • Question asked 2018-02-23 08:50:27 ... Most recent comment 2018-03-04 14:27:38
    Question

    I've been trying to fix charcoal to the surface of my paintings, ie drawing on top of dry oil paint. The paintings are sometimes on linen and sometimes on hardboard/plywood, not large, about 30-40 cm. I want the charcoal to adhere permanently and remain on top, not be painted over. I know this is not seen as good practice but artists have done it and I wondered how it has been fixed. Obviously a charcoal line has a quality like nothing else and I want to retain that. 

    I've been using Schminke Universal-Fixitiv 50-401, which apparently contains Benzotriazol-Derivat, dimethyl ether, polyvinyl resin, n-butyl acetate, UV-absorber, alcohols.  It seems to stick the charcoal, anyway for a while, but after 10 days or so, when I wipe the surface very gently some charcoal comes off, which it hadn't at the start. Schminke say their fixative isn't meant to fix charcoal permanently as a top layer, just to paint over.

    I don't varnish my work because it may need to hang before it is totally dry and also I often return to a picture to rework something. I wondered whether the best way of keeping the charcoal fixed might be to wipe stand oil, or perhaps poppy-seed or some other oil, lightly  over the charcoal after fixing it first with the Schminke fixative? Would it in effect incorporate the charcoal into the oil paint?  I have tried it on one picture and it didn't smear but I wondered about permanence?



  • Question asked 2018-02-19 20:09:44 ... Most recent comment 2018-02-25 14:35:54
    Rigid Supports
    Question

    I am trying to build an archivally sound canvas substrate. How much chance is there of a 16 oz tightly woven canvas fabric slackening over time if tautly and very evenly stretched on a cradled panel with the strong fibre being placed in a vertical direction? Does the fact that it is a rigid support lessen the chances? If the fabric is tacked, and therefore quite adjustable, can this perform as well as a keyed stretcher for adjustments in the instance where it might need any adjustment? Over such a panel, is use of linen necessary to prevent destabilizing the substrate by slackening, or is it overkill?

  • Question asked 2018-02-16 16:04:02 ... Most recent comment 2018-02-19 18:39:00
    Oil Paint Grounds / Priming Alkyd
    Question

    I have an oil painting in progress that has a quite-dry, scrubbed-on Imprimatura layer of M. Graham Rapid Dry Titanium -- an alkyd oil paint which *does* have a small percentage of Zinc in it, according to the company, and which I used as an oil-based 'ground' alternative to something like a solvent-based ground because an acrylic-primed canvas is so dang absorbant and 'draggy' -- that was then painted over with a very thin raw umber layer with a small amount of alkyd medium. It's been a month now, the raw umber appears quite dry, but a fingernail can scratch off the paint on the high points of the canvas weave. I'm wondering if this is just happening within the normal curing and bonding time between layers of oil paint, or if the Rapid Dry used as a Ground was not a good idea, or there's some other red-flag reason not to proceed with this approach? Any thoughts would be much appreciated!

  • Question asked 2018-02-16 16:14:36 ... Most recent comment 2018-02-17 05:06:45
    Question

    ​This may not be news to our conservation experts, but this researcher found me via Utrecht's social media presence when I posted about herringbone canvas. I think this is fascinating! https://handwovencanvas.blogspot.pt/

  • Question asked 2018-02-13 11:34:04 ... Most recent comment 2018-02-13 21:07:21
    Industrial and Non-Traditional Products
    Question

    ​I know this is probably a too vague question... From what I've studied so far, it seems that ACM panels are an almost perfect surface to paint on (after being properly prepared for that).

    Then a friend questioned my belief and told me that copper was actually superior to ACM panels, at least for oil painting. I have some doubts yet I couldn't fail to notice that the paintings on copper  that I've seen are much better preserved than the ones on other traditional supports.

    What is the very best support for oil paints currently available?


    Thank you!

  • Question asked 2018-01-31 10:35:37 ... Most recent comment 2018-02-11 19:01:19
    Drying Oils Oil Paint
    Question

    ​Hello all,

    I hope you can help advise me on a problem I have. I painted a portrait 6 weeks ago using tubed paints (mostly W&N Artist Oils and Rembrandt) mixed with walnut oil and clove oil - no solvents used. It is painted in one thin fluid (but opaque) layer on a rigid support with two layers of acrylic primer with a strong tooth.

    I have done many of these kind of paintings with no issue as the extended drying time is very useful. However on this painting once it was done I stored it in a cardboard box with ventiliation with 4 open areas covered with dust meshes (the kind you see on PC computers cases over the fans) to let out the evaporating vapours of the clove oil and to let in fresh oxygen.

    I had no problem with the previous painting I painted and stored in this manner. However on this portrait I find that some sections are still not dry after 6 weeks (now outside the box in warm air for 2 weeks). It's not the whole paint film, it's almost like just the surface of the paint, and it's a thin (but opaque) paint layer I use anyway. Not all of the painting is affected, but the parts that are don't seem to be affected.

    I can only thing I could think of as to what has happened is that the vapours of clove oil stayed in the box too long from this and the previous painting and degraded the polymers enough that the paint now will not oxidise.

    I was thinking about my options, and I have come up with these so far:

    1. Continue to store in a well ventilated and warm environment and see if it oxidises (not sure it ever will).

    2. Try a spray siccative like Krylon Quick Dry Spray (and hope the paint does start to cross-link).

    3. Wipe off what damaged paint I can and repaint.

    4. Try to apply a thin layer of walnut / linseed oil to the affected areas (staying within each hue/value area as best I can) to try to add a drying oil onto that section and bond with the pigments remaining.

    5. Nothing can be done. Redo the painting on another panel.


    Does anyone here have any suggestions on how best to proceed?

    Thank you!
    Richard

  • Question asked 2018-02-08 09:22:35 ... Most recent comment 2018-02-08 11:52:24
    Industrial and Non-Traditional Products Storage Sizes and Adhesives
    Question

    ​An artist recently contacted me to ask for a recommendation for a type of adhesive. They are using latex to create cast forms (think Eva Hesse) and would like to adhere panels of latex together. They are unconcerned with the inherant vice of the latex itself, but they are concerened about the compatability of the adhesive with the latex, its flexibility, comparative aging and of course its efficacy. Does anyone have any experience in this area and could they also recommend some basic and easy to implement storage ideas for when the work is not on display? Many thanks in advance.

  • Question asked 2018-02-05 22:36:01 ... Most recent comment 2018-02-07 17:05:54
    Art Conservation Topics Flexible Supports
    Question

    ​When AMIEN was active, there was a consensus that cotton was fairly equal to linen as far as longevity is concerned.
    It makes sense to me that linen would be stronger because of the longer thread length.
    Is there any evidence from older paintings that there is a significant difference in longevity?

  • Question asked 2018-02-06 19:21:16 ... Most recent comment 2018-02-07 12:28:41
    Acrylic
    Question

    ​I am planning a number of works that involve painting in acrylic on papers prepared with acrylic gesso with 2 coats on each side.  These papers will be mounted to a sealed plywood panel when finished. My question is with the mounting and sealing, will 100% rag papers perform drastically differently than acid free alpha cellulose papers? Or can I treat acid free alpha cellulose papers as I might treat an extremely thin piece of tempered hardboard?

  • Question asked 2018-02-01 08:27:20 ... Most recent comment 2018-02-06 10:36:50
    Paint Making Acrylic Other
    Question

    ​Hi,

    At the moment I am testing Chroma Color from a Spanish factory called La Pajarita. It seems Artists like Dali have made use of their paint. I am trying to find out if it would be suitable for our Shop in School, of my Art Academy.

    The one thing I am concerned about is that it is made with vinyl in stead of acrylic. I was under the impression that acrylics are superior to vinyls. As far as I know the plastcisers in acrylics are internal and often in pva's external, am I right?

    According to them, however, when they were considering transition from vinyl to acrylic as a binder, their vinyl tested better then most of the acrylics from their competitors. And that is why they stayed with vinyl.

    My knowledge is too limited, here. So I hope you people can help me out.


    Thanks


  • Question asked 2018-02-05 11:11:56 ... Most recent comment 2018-02-06 02:30:19
    Question

    ​Hi all,

    I was wondering whether anyone had any thoughts on using Frixion pens for underpainting? The idea being that even under transparant paint the drawing can be made transparent with the application of heat..

    I know that the ink they use becomes transparent at 65C and then stays that way until the temperature is lowered to -15C. 

    I don't know if subjecting oil & acrylic paint on top of the ink to temperatures that high for enough time to activate the fading process in the ink would cause damage to the paint films?

    Has anyone done any tests or studies on this, or seen artists using them for underdrawing?

    Thank you,
    Richard

  • Question asked 2018-02-02 21:55:38 ... Most recent comment 2018-02-03 12:27:44
    Rigid Supports Sizes and Adhesives
    Question

    Hello. I had a very large linen stretched, because I like the tooth ofl linen. However, having never done anything this large, I did what I could but after sizing (1 coat GAC 400 and one coat GAC 100), the linen is VERY loose.

    Two options: Re-stretch, or mount on Birch ACM.

    I would prefer to mount on ACM, but I want to double check what the right process is here.

    Is BEVA the approppriate adhesive to use? Does it matter what variety I use? Is there a better adhesive?

    Are there any considerations when choosing an ACM? I would probably use Omni-bond, not sure if that brand is one you recognize or if BEVA on it's own will give me adequate adhesion.

    Would it be wiser or easier to simply use a birch panel?​

    Any help is very appreciated. I did search, but couldn't find an answer. 

  • Question asked 2018-01-25 14:02:29 ... Most recent comment 2018-02-03 11:27:02
    Other
    Question
    I have read that vinyl-based paints suffer some degradation when subjected to variable and harsh atmospheric conditions, and that they perform overall worse than acrylic-based paints. However, I couldn't find any information about works that are only meant to be kept inside. Would there be any significant difference? As an additional question, would applying a layer of acrylic medium over the vinyl paint add some protection?

  • Question asked 2018-02-02 15:09:04 ... Most recent comment 2018-02-02 16:58:22
    Oil Paint Industrial and Non-Traditional Products
    Question
    I have read that non-drying oils (baby oil, sunflower oil, other cooking oils) can be used for brush cleaning at the end of a painting session, so long as they are then cleaned with soap to remove the non-drying residue. However, from my experience it's usually not possible to remove absolutely all of the substance that was on a brush. I would like to know if the usage of non-drying oils as a cheap (and healthier) alternative to solvents is advisable? Wouldn't it be better to use linseed oil and soap, or just soap?
    I also remember another suggestion, which was to keep the brush tips submerged in oil (walnut or linseed) in a tray instead of washing them with soap and letting them dry. Would that be advisable?
  • Question asked 2018-01-31 18:43:27 ... Most recent comment 2018-02-02 12:47:21
    Oil Paint
    Question

    Is the practice of using only oil - without any solvent - sound? Presuming I don't use an excessive amount of oil (meaning, one that would create a layer of its own, separate from the paint), would the produced paintings be technically sound, from a conservation standpoint?

    Assuming that this is the case, is there any sound way to speed up the drying time without toxic chemicals (siccatives etc.)?

  • Question asked 2018-01-30 17:25:17 ... Most recent comment 2018-01-31 17:31:55
    Health and Safety Oil Paint Solvents and Thinners
    Question

    ​It's fairly easy to find information regarding Chronic Solvent-induced Encephalopathy/Chronic Painter's Syndrome. CSE is a nervous system disorder that is characterized by cognitive impairment and other psychological changes following long-term exposure to organic solvents, even below threshold levels.

    A question that comes to my mind is: how much at risk are artists? All CSE studies I've read involved industrial painters/cleaners who inhaled a lot of xylene, toluene, mineral spirits, and other substances as a part of their daily work routine. However, most oil painters nowadays would likely be exposed to at least one kind of organic solvent on a daily basis as well. I was wondering if there is any information regarding the following products:

    • Odorless Mineral Spirits (the regular mineral spirits are already known to most likely cause CSE)
    • Turpentine
    • Oil of spike lavender
    • Naphtha

    and other solvents likely to be found in the studio, with regards to the neurological damage they can cause? How much turpentine/OMS/etc. can I inhale on a daily basis without risking health damage? Is there any substance on the list which is safe given chronic exposure? (I read that oil of spike lavender is supposedly safe, but retain some scepticism, given its solvent strength)

  • Question asked 2018-01-27 21:42:19 ... Most recent comment 2018-01-29 20:48:11
    Drying Oils Solvents and Thinners Oil Paint
    Question

    ​Referring to your article about paint mediums and additives.
    Link https://www.artcons.udel.edu/mitra/Documents/MITRA_Mediums_and_Additives.pdf

    [quote]"Consider painting without using solvents. If you are using solvents, use smaller and smaller additions of solvent as you continue to paint subsequent layers to follow the “fat over lean” rule of thumb."[/quote]
    I define the fattness of a paint film as the oil to pigment ratio, as does George O'Hanlon I believe. (PVC, Pigment Volume Concentration.)
    In this respect, adding solvent to oil paint won't make it any leaner as the paint film with end up with the same PVC as it had originally before the solvent was added.
    Granted, it does allow one to paint more thinly and therefore dry more quickly, but I can easily demonstrate that one can spread neat paint very thinnly and solvent added paint thickly.
    So with this in mind, I question the premise that adding less and less solvent is adhering to the fat over lean rule.
    I mention this because the text above is being quoted as proof that adding solvent makes paint leaner.
    Is there any other rational that would give the argument more credibility?

  • Question asked 2018-01-28 15:16:11 ... Most recent comment 2018-01-29 10:18:29
    Oil Paint
    Question

    ​After an oil  painting was stored in climate controlled facility for 8 years, yellow patches appeared in areas of the painting. The medium was alkyd based like Winsor Newton Oleopasto. The painting was stored in styrofoam and corrugated cardboard. Was there off gassing of the storage materials causing some yellow passages? Or, the effects of total darkness? Is there a way to correct without removing varnish and paint layers?

  • Question asked 2018-01-27 16:25:15 ... Most recent comment 2018-01-27 22:42:29
    Varnishes
    Question

    ​Hello Mitra,

    I would like to first say thank you everyone from Mitra  for their continual help.  

    I recently heard of teachers at an academy, that I will not name, telling their students that they could place a final varnish of a polymerized oil like a stand oil.   They are told that this is actually what many of the old masters did and that other varnishes are not necessary.  Is a polymerized oil, like a stand oil, suitable for this?  During your experiences have you ran across any masters that did this? 


    Best Regards,

    Hector



  • Question asked 2018-01-26 08:31:50 ... Most recent comment 2018-01-26 09:08:55
    Acrylic Animal Glue Grounds / Priming
    Question

    Hi,

    I have a friend who applies traditional gesso using a spray gun.  In recent batches she's been getting an especially large number of pinholes.  I've suggested various things that, in my experience, address pinholes (such as: letting the gesso sit overnight, once it's made, to let bubbles dissipate, then rewarming and applying it; not having too great a temperature differential between the gesso and support; applying the gesso very thinly; not waiting long between layers) but she is still having problems.  I don't use a spray gun and get no pinholes in my gesso, so I'm not sure what further to suggest.  

    I'm wondering if adding a small amount of Golden's Flow Aid might help, but I'm not sure how acrylic polymers (albeit a very minimal amount) work within traditional gesso.  When I first began making gesso (25 years ago) I read about adding sugar (1 tea. sugar to 2 cups gesso) to help with pinholes, and I tried doing that a couple of times - it seemed to work fine but was so many years ago I can't really remember.  What about that idea?

    Any other suggestions for how to address pinholes?

    Thanks,

    Koo Schadler

  • Question asked 2018-01-11 19:49:01 ... Most recent comment 2018-01-23 01:13:28
    Paint Making
    Question

    ​Brian and George, I was totally blown away by your fast, and thourough response. Thank you so much.

    I limited my questions to two per visit like I have to at my family physician, but I actually have one more, also about Lead-White.

    After repeated levigating, and grinding the Lead-Carbonate flakes, (in a ball mill with ceramic media), I start doing the rinses, usually about ten.  Residual Lead-Acetate is found to be present in at least the first four rinses when tested for with Sulfuric Acid.

    I precipitate the Lead-Acetate out with Sulfuric Acid, or Sodium Bicarbonate, to end up with Lead-Sulfate and Acetic Acid, or Lead-Carbonate and Sodium Sulfate (environmentally safe concrete sealer).

    The Lead-Sulfate is re-combined later with the Lead-Carbonate through a last grinding, followed by distilled water rinses. I read somewhere that this makes a better (oil) paint then if either one was used alone. 

    I would very much appreciate your opinion on this.  BTW I will now also return the pigment from the foam to it`s respective Carbonate.

    Thanks, Niq

  • Question asked 2018-01-17 13:01:48 ... Most recent comment 2018-01-19 15:23:14
    Acrylic Oil Paint Other Watercolor
    Question

    ​Would anyone hazard a method for a "durable" approach to using oils over an acrylic underpainting, which also possibly has collage elements? I am particularly concerned about oil delamination, drying time between acrylic layer and subsequent oil layers, best thinning medium for the acrylic layers, and the ideal substrate. Any thoughts or links to articles would be greatly appreciated. I know there are contemporary well-known artists who use this approach and have not read anything about their paintings falling apart. I am also wondering if watercolor could be used as the initial layers instead of acrylics, and any caveats about that approach. Basically, I'm looking for a quick way to get a painting started without the traditional use of solvents for this underpainting or initial rough-in layer. Thanks!

  • Question asked 2018-01-17 11:40:07 ... Most recent comment 2018-01-17 20:00:28
    Rigid Supports Sizes and Adhesives
    Question

    Would a pva glue with a ph of 4 be suitable to mount primed linen to hardboard?​

  • Question asked 2018-01-10 18:07:22 ... Most recent comment 2018-01-11 15:57:50
    Varnishes Art Conservation Topics
    Question

    ​I would like to know if I need to prepare an acrylic painted surface for oil crayons to make it stable over time, and the best medium to seal the final surface.

      Also, is clear gesso the best medium to use over acrylic to prepare the surface for cold wax, what do I need to add to a low ratio of paint to wax? Do I understand correctly that using less than 2/3 paint to 1/3 wax is inadvisable without adding other mediums? I have found recipes online but no consensus.

    Thank you


  • Question asked 2018-01-11 10:46:55 ... Most recent comment 2018-01-11 12:51:04
    Paint Mediums Oil Paint Solvents and Thinners
    Question

    ​I glaze using oil paint. I need to know if I have used Gamblin solvent free gel or fluid can I then use walnut alkyd oil on the same painting? I prefer walnut oil, but am not always allowed to use it if the venue is nut free. 

  • Question asked 2018-01-11 00:13:39 ... Most recent comment 2018-01-11 10:42:19
    Paint Making
    Question

    ​Does a "good" lead white need to have some lead-acetate left in it, or should it all be removed by repeated  and thourough washing ? Alvah H. Sabin in "White Lead its use in paint" 1920, questions this and proposes that up to as much as 5% acetate of lead should be left in, or added, to make a better paint. I am aware that he is talking about house paint, but has this merrit ?

    In " Mannel des jeunes Artistes et amateurs en peinture" 1831 , M.P.L. Bouvier writes that to use lead-white for watercolour we must take a twig from white wood, peel the bark off, then whip up the lead-white pigment while in water, and only use the froth/foam. After testing the foam/froth from five different batches of lead-white paint I produced, I found no traces of lead acetate while the supernatant had the usual acetate content. Is the foam/froth a different make up then ?


  • Question asked 2017-12-16 03:20:42 ... Most recent comment 2018-01-09 14:27:42
    Gilding
    Question

    ​Three questions:

    1. I would like to add portions of burnished gold leaf to my oil paintings. I have oil gilded on canvas before and though the results were fine I much prefer the look of burnished gold. Which support would be best suited for this? Gessoed ACM? Gessoed Panel?  

    2. I have read you cannot burnish oil gilding but have never seen the reason why. Why can't you burnish oil gilding?

    3. I would also like to gild a ram skull. Archivailibity is less inmportant in this case but I would still be pleased to do it in an archival manner. Which mordant should I use and should I prepare the bone in any particular way?

  • Question asked 2018-01-03 18:14:30 ... Most recent comment 2018-01-04 15:57:49
    Rigid Supports Grounds / Priming
    Question

    ​I plan to seal some panels of 1/4" premium, tempered hardboard (Alpena hardboard from DPI, not the big box store variety) in preparation for mounting 140 lb, wc paper to it with acrylic dispersion medium.  

    The liquid shellac comes usually in a 3 lb cut (3 lbs shellac per gallon denatured alcohol).

    How far should I dilute it with denatured alsohol?  50-50 ? 33-66? other?


    Thanks for your help.

    Richard

    PS  I'm going back to shellac as a sealant rather than acrylic dispersion medium in order to minimize water and the warping of the 10 x 20", uncradled panels. 

  • Question asked 2018-01-02 23:10:06 ... Most recent comment 2018-01-03 20:41:30
    Drying Oils Paint Mediums
    Question

    ​Hello Mitra,

    I wish to bleach my linseed oils by letting the sun hit them.  I was curious to know if i could do this to an already polymerized oil like Stand Oil?  If not, I take it a cold press linseed oil is the best to use for starting.

    My goal is to have a viscous clear oil which if need be I can then make it more fluid with a clear cold press oil.

     I know traditionally artist would wash their cold press oil and then thicken it and bleach it through exposure of the sun.  Should I do this? Is my Stand Oil a lost cause then? 




  • Question asked 2018-01-02 07:41:09 ... Most recent comment 2018-01-02 10:03:21
    Oil Paint Acrylic
    Question

    ​Do all paints have surfactants in them?

  • Question asked 2017-12-31 09:23:24 ... Most recent comment 2018-01-01 06:35:36
    Flexible Supports
    Question

    ​Happy New Year dear Mitra people

    I have been struggling to find a way to glue primed polyester canvas to Masonite (Hardboard) panels. My problem is that the canvas is fairly lightweight and very prone to deformation/ wrinkles. My attempts to glue it to panel so far havent been very successful. I keep getting little air pockets under the polyester canvas, despite using a roller to push the fabric down and weighting it with heavy books etc. I’ve tried PVA, acrylic matte medium gel, solvent based contact adhesive and acrylic based contact adhesive. So far, the  best results have been with the solvent based contact adhesive—but the fumes are dreadful. (I am aware of the measures I must take to avoid hazardous exposure to them by the way) and I’m not too sure about it’s soundness from a conservation POV. I thought it might help to stretch the canvas on a stretcher, then stiffen it with rabbit skin glue, then remove it and glue it to a panel. Unfortunately it’s almost as difficult to stretch as it is to glue down. So I’ve given up on that idea. My next plan is to use rabbit skin glue to glue it to the panel. I am aware of all the problems associated with rabbit skin glue but still feel (or should I say hope) it will work better than anything else for my purposes. It also has the advantage of being reversible. My questions are : what ratio of RSG to water would you recommend? My old Painters Handbook (like all art technique books) contradicts itself. On one page it recommends the same ratio as normal RSG size (1 part rsg to 10 parts water). But then tucked away on another page, the suggested ratio for RSG as an adhesive is given as 3 parts to 10 parts water. I seem to remember that Ralph Mayer recommended a recipe that was similarly stronger for RSG as an adhesive as opposed to as a size, But I can’t find that reference currently despite looking for it in my old book.

  • Question asked 2017-12-31 00:11:06 ... Most recent comment 2017-12-31 01:18:22
    Oil Paint Acrylic
    Question

    ​What are the ingredients in making the "vehicle" for oil and acrylic paints? What are the chemicals in making acrylic and oil paints? I understand that the colors are made from differing chemicals and this is a complex question.

  • Question asked 2017-12-30 20:46:36 ... Most recent comment 2017-12-30 20:59:18
    Technical Art History
    Question

    Hello Mitra Conservators,

    Could you so kindly list technical/technique books that you would highly recommend?  

    For example the N.G. Technical Buletins, and Sir Charles Eastlakes book come to mind, but im sure there are others and maybe even better ones that Mitra could recommend.

    I recently heard of one by Mary Merrifield titled, "Medieval and Renaissance Treatises on the Arts of Painting,"  but im not sure if this is something Mitra Conservators would put on their list.  

    Thanks you and Take care

  • Question asked 2017-12-28 21:01:06 ... Most recent comment 2017-12-30 11:07:45
    Oil Paint Acrylic
    Question

    Are paint fumes bad for your health? If so how and why?​

  • Question asked 2017-12-27 16:15:15 ... Most recent comment 2017-12-29 21:22:07
    Oil Paint
    Question

    ​Hello Everyone, I am seeking advice about old dried mold stains on stretched gesso-primed canvas.

    A few points:

    • The canvas is one I began 20 years ago and has been in storage since. When I retrieved it recently from storage, there were mold patches on both front and back of the canvas. (the front is gesso priming on cotton duck. The back is not primed; just raw cotton)
    • The mold is not extensive, only in the corners near the edge.
    • The moldy patches are on both the front and back side.
    • The mold is not heavy, it just appears as a light stain behind the image.
    • The mold appears to have dried years ago. It does not appear to be advancing, but the stains remain.
    • This painting is an underpainting, a single color of very thin paint (washes with oil paint & turpentine)
    • There's no heavy layer of paint on this canvas yet, just the thin wash drawingwhich is quite transparent. The mold stain appears behind the transparent underpainting. I could easily finish the painting which will cover the mold.

    Questions:

    1. If the mold is fully dried, is it safe to go ahead and paint on this canvas, as is?
    2. Or should I try to remove the stains before I resume painting on this canvas?
    3. If I do finish this painting, will there be subsequent damage from the mold being 'trapped' beneath new paint?

    Thanks in advance to anyone to offer me some guidance with this.

    Cheers.

  • Question asked 2017-12-24 04:45:25 ... Most recent comment 2017-12-24 16:28:57
    Question

    Just want to say Merry Christmas and a great big thank you for everyone's help here. It's really reassuring for artists to have your help and advice (especially when it's out of your own time)!

    Thank you!!​

  • Question asked 2017-12-20 17:05:50 ... Most recent comment 2017-12-20 17:48:37
    Oil Paint Acrylic
    Question

    ​I would like to know what is in them when we buy them. The medium(s) that turn them from a pile of chemicals to a liquid paint in a tube or jar etc.

  • Question asked 2017-12-17 17:47:56 ... Most recent comment 2017-12-19 16:25:05
    Ink
    Question

    ​Will Indoor air exposure reduce a Moisture buildup and greasy film on the exposed duralar surface of an Acylic ink painting? Moisture and film develped on a painting within a frame when the duralar moved towards and pressed against the glass inside the frame. Is there something safe to use to remove the film.

    Kremer Primal AC35 was used on the ink area.

  • Question asked 2017-12-15 19:44:40 ... Most recent comment 2017-12-18 22:39:48
    Acrylic Grounds / Priming Other Paint Mediums
    Question

    ​I am making some “ Calder like” Mobiles but instead of just spray painting them I’m interested in painting them using Acrylic paint.  Has anyone had experience with this and if so what is your experience/ pitfalls etc.? As well, I would like to know what kind of Primer or Ground that I would have to apply as a first protective coat ...I.e. once the metal is cleaned can I just spray on an off the shelf rust free Primer paint  or is there a material that I could use that would work better...e.g. gesso, medium etc?

    Thx. Hy

  • Question asked 2017-12-15 23:09:45 ... Most recent comment 2017-12-18 10:25:41
    Oil Paint Grounds / Priming
    Question

    ​Hello,

    I've been working on a soapstone carving and have produced a ton of dust in the process. I was wondering if I can use it in place of marble dust to make gesso? Would it be a stable ground for oil painting?

  • Question asked 2017-12-14 21:23:38 ... Most recent comment 2017-12-17 12:28:47
    Gouache Matting, Framing, and Glazing Oil Paint Watercolor
    Question

    ​Hello MITRA folks ~ From a conservator's standpoint, can you tell me if there is justification for the wide-spread perception that watercolors are "fragile" and a "poor long-term investment" relative to an oil painting? I've always reasoned that an oil painting is *far* more prone to damage and degradation in both the short and the long term compared to a well-framed watercolor (modern lightfast paints, acid-free materials and UV glazing), since there is, at best, only a thin varnish to protect the oil's surface. Thanks for your thoughts.

  • Question asked 2017-12-14 10:47:16 ... Most recent comment 2017-12-16 19:04:32
    Paint Mediums
    Question

    ​Has there been any modern improvement upon casein secco painting media after buon fresco (lime plaster) wall painting. Specifically, are there synthetic media (acrylics or alkyds etc.) that work well with lime? I was curious to know if anyone may have tried Zecchis "secco" paint that indeed contains an acrylic binder, however I am not sure what else may be in it. and i am not sure that it was intended for lime plaster buon fresco.

  • Question asked 2017-12-13 11:04:29 ... Most recent comment 2017-12-16 18:32:52
    Flexible Supports
    Question

    ​I have been researching commercial, cotton, oil painting papers by D'Arches, Canson, etc, for detailed, preparatory studies that I may or may not mount and sell.  

    Do you forsee any problems with 100% cotton papers by these or other companies?

    The paper fibers are protected, according to their literature, but the OMS and oil can be drawn down below that surface somewhat, unlke the pH neutral PVA size layer tha I put on my papers before use.   Perhaps this affords more tooth for the paint layer to attach to.

    Any thoughts?

    Thank you.

    PS   I avoid priming papers as I will thereby lose the very texture that I like in the paper, and have been sizing only.   Also, the investment in time and material makes them so "precious" that I may not be as likely to experiment with them.   I have followed the directions sent by Robert Gamblin some 15 years ago.

  • Question asked 2017-07-09 17:43:58 ... Most recent comment 2017-12-15 20:04:20
    Acrylic Rigid Supports Sizes and Adhesives
    Question

    ​I want to try using thick, solid cardboard as a surface for acrylic painting, but I can't get any information about its archival properties (lignin, acidity) from the manufacturer. I found a recipe on an acrylic paint manufacturer's website that calls for coating the entire sheet with a couple of layers of gloss acrylic medium-varnish so as to make a layer onto which one can paint. Supposedly, if any problems arise in the future (from what I know, it's inevitable with cellulose), a conservator will simply be able to dissolve the cardboard and reline the acrylic painting.

    I would like to ask how viable this idea is.

    Also, I thought about whether it would be more likely to work if I:

    1. saturated the cardboard with something (gelatin/methylcellulose/PVA/wall paint primer?), then
    2. gave it three layers of gloss medium (first diluted 1:1), then
    3. put on two layers of acrylic ground

    and then painted on it? I'm not sure if three layers of medium plus two layers of ground wouldn't be too excessive.

  • Question asked 2017-11-30 13:09:30 ... Most recent comment 2017-12-10 10:30:58
    Oil Paint Pencil Drawing Materials
    Question

    ​From a durable standpoint, can you tell me if drawing lines into wet oil paint with a graphite pencil is a sound practice? (On both stretched canvas and on panel.) Ultimately, the finished paintings would be varnished. I've Googled this question and come up with nothing...thank you!

  • Question asked 2017-06-15 16:48:30 ... Most recent comment 2017-12-09 22:02:38
    Oil Paint Paint Additives Paint Making
    Question

    ​GReetings, 

    When making oil paint or modifiying oil paint with additives, how do you determine the ratio of pigment to oil, say titanium white with marble powder to linseed oil? 

    There is a point when the paint becomes very thick and will even roll off of the mixing plate glass, and this is obviously too much pigment to oil. Are oil absorbtion rates needed, if so are these online?


    Thank You

  • Question asked 2017-12-08 17:31:10 ... Most recent comment 2017-12-09 19:18:03
    Technical Art History Oil Paint Paint Mediums
    Question

    Hi-

     

    I'm rather old school and I can't afford to switch to walnut oil and lavender I have to keep it simple.  I paint a lot and on a large scale. I would say my application of paint is on the wet loose side and most likely too much vehicle and medium is slapped around by your standards

    As I get older I am concerned with my health, if it is not too late, so I  have begun to rethink my formula of 40 years:

     1:1:1

    Turp- Dammar -Linseed oil

    I begin with gum turp and progress to a fatter medium.

    Occasionally I add stand oil to the brew.

    I have experimented with adding egg yolk, using liquin and alkyd mediums. I'm happy with my old "go to" but for the fumes. I occasional remove dammar from the mix. Any ideas of a formula or medium that would suit me. Any big issues with the 1/3, 1/3, 1/3 mixture I use?

    Thanks

  • Question asked 2017-12-08 18:53:25 ... Most recent comment 2017-12-08 22:05:00
    Flexible Supports Studio Tools and Tips
    Question

    ​I recently had occassion to remove several less-than-satisfactory paintings from their stretcher bars (in preparation for attaching new canvas) and discovered that these brand-name, pre-stretched canvases had been stapled on the corners of the bars on the front side. Am I understanding that this practice of stapling the corners of stretcher bars totally defeats the function of "wedges" for adjusting loose canvases? Thanks for your thoughts.

  • Question asked 2017-12-08 05:34:33 ... Most recent comment 2017-12-08 16:32:06
    Oil Paint
    Question

    ​Can anyone please point me towards a scanning electron microscope image of the surface of a sunken in oil paint swatch, and preferably an image of a glossy swatch for comparison, that I could use for a teaching slide? Thank you.

  • Question asked 2017-12-05 22:08:25 ... Most recent comment 2017-12-06 12:45:58
    Sizes and Adhesives
    Question

    In 2015 I contacted Gamblin asking for directions on a substitute product to RSG for sizing canvas.  The recommendation I received were instructions, developed by Robert Gamblin and Ross Merrill, former head of Conservation at the National Gallery, in point form.  After a few steps on how to glue canvas to a wood panel, Step 6:  Apply Gamblin PVA size to protect the surface of the canvas with one penetrating coat.

    I decided to purchase the PVA Size and after a few tests, and problems with the ground being too absorbent, I decided to apply 3 coats instead of 1, sanding and scraping before applying the last coat.

    On a Facebook forum I was informed that Gamblin PVA size had been tested by Sarah Sands (article dated 2013, Preparing a Canvas for Oil Painting | Just Paint,)  She tested the PVA size along with other products, and her findings showed that Gamblin PVA Size performed poorly, both in terms of flexibility and strikethrough.

    I am a bit puzzled by this:  Gamblin is providing me with instructions with big names undersigning them, plus "National Gallery" and the "Canadian Conservation Institute" are mentioned on the labels and online.   But then you have Sarah Sands, doing an honest test, showing that the Gamblin PVA size should not even have the name 'size' on it.  I am no expert, but I can read a chart.

    My question is, what is going on here? 

  • Question asked 2017-12-05 14:05:54 ... Most recent comment 2017-12-05 23:03:50
    Pigments Oil Paint
    Question

    ​Hello all,

    I have long wondered about certain pigments still used in quality artist paints that are rated as less than excellent in terms of lightfastness: in what situations will they tend to fail, and how might we best use them to achieve lasting results? Some of the pigments I have in mind are PR112 (Napthol red), PY3 (Arylide Yellow),   or even  NR9 (Madder Lake). It's my understanding that pigments such as these are much more prone to fade in tints, but I'm wondering if there are any applications that are considered truly lightfast, such as in glazed top coats etc..

    This question is primarily about these pigments in oil paints but i'd welcome any insights regardless of medium.

    Thank you very much in advance for any advice you can offer, and thank you all for the work that you do!

    Bob

  • Question asked 2017-11-19 11:56:20 ... Most recent comment 2017-12-02 17:17:43
    Acrylic Grounds / Priming Oil Paint Rigid Supports Flexible Supports
    Question

    ​In the Resource section (Grounds & Primers) MITRA states that, "Even though acrylic grounds/paints appear to dry within 24 hours, moisture continues to evaporate from these materials over an approximate 30-day period." Does this mean that supports (both canvas and panel) primed with Acrylic "Gesso" should not actually be painted on (this would be for oils) until *after* this 30-day period has passed...?

  • Question asked 2017-01-03 15:41:54 ... Most recent comment 2017-11-30 09:04:46
    Paint Additives Paint Mediums
    Question
    I don't know what to make of the claims of a medium made of copal resin that is modified with heat  and mimics the charactoristics of the older fossil forms of copal or so says its makers. It is relatively new and is a gel. Is this possible? I have read about the more desired effects of the older (fossill ) forms of this resin and would like to know about the virtues and shortcomings of copal in general.
  • Question asked 2017-11-23 19:22:07 ... Most recent comment 2017-11-26 21:00:27
    Oil Paint Rigid Supports Grounds / Priming Acrylic
    Question

    ​Greetings MITRA folks. Can you tell me if oil painting directly on a shellaced panel is an accepted and durable practice? I know of at least one company which sell panels that have been "sanded and shellaced on both both sides and edges with a wax-free shellac," and they are advertised as a "ready-to-use painting support." I know of both acrylic and oil painters who use these particular panels, but I do not know if they are adding an oil or acrylic ground over the shellaced surface before proceeding with oils. Knowing only of shellac from a furniture sort of standpoint, I would have thought that shellac as a surface for oil paints *directly* would be too slippery and would have poor long-term adhesion. Would you kindly set me straight on this subject? Thank you! 

  • Question asked 2017-11-22 14:19:04 ... Most recent comment 2017-11-26 19:14:00
    Chalk Paint Mediums
    Question

    ​Hello Mitra,

    I wish to mix calcium carbonate to my paints to give them more body and also to maintain them a bit more transparent. Is their a specific calcium carbonate that I should purchase for what i want to do? Or is it all the same?  Chalk? Marble dust? etc?

    Can I mix it directly to paint from tubes ,or should I start from scratch with powder pigment?  

    Thank you ,

    Hector



  • Question asked 2017-03-13 10:36:30 ... Most recent comment 2017-11-26 13:20:53
    Alkyd
    Question

    I looked at previous posts but still find the advice I've seen on using alkyd mediums a bit confusing and contradictory. On one hand I've read that it is best to use alkyd mediums only in lower layers because you want faster drying layers under slower drying layers. This makes sense to me. However, I've also seen recommendations from manufacturers to increase the amounts of alkyd medium in subsequent layers to maintain fat over lean (more flexible over less flexible?) but that seems to contradict the slow over fast drying concept. Ultimately, I would like to use M. Graham solvent free  walnut akyd medium in the underpainting/blocking in and then straight oils in subsequent layers. Would I need to worry about a) adhesion between the first and second layers or b) violating fat over lean/ more flexible over less flexible? 

  • Question asked 2017-11-25 11:39:09 ... Most recent comment 2017-11-26 11:31:44
    Sizes and Adhesives
    Question

    ​Hi! Im an art student at the National academy of fine art Oslo, Norway.   

    I'm interested in using raw linen canvas in my painting, I've previously bought white  grounded linen and stretchid it the unprimed back as the front. Recently, I received unprimed linen from artist store.

    I have experience with rabbit skin glue but since i want to use oilpaint directly on the "size" this is not on option?. I started using artist grade PVA, and a professor tought me how to dilute it with water, ca 1/5 pva to water. it worked well with two coats on cotton but when i started priming the linen the result was really horrible.

    i stretched the raw canvas nicely and tight on a stretcherframe and started brushing on pva/water.  while wet the linen got really firm and tight but after drying overnight the canvas was completely slacking.  after yet another coat the canvas was tight (wet) and later turned slacking but hard as the pva dried.  i made tests where i put on the pva undiluted and the result was good but the pva layer dried almost instant, it was uneven and slighly milky plastic looking.  

    I also started pva priming the canvas unstretched and later had to really struggle to force the canvas to get tight on the frame with canvas pliers, as it did not get really stretched i made the huge mistake to brush some water on the canvas, it get really bad after drying, untight and full of ripples. i have made alot of searching for answers, my proffessors just told me that the key is to dilute with water, and restretch the canvas and give it more glue coats. wich i did, and every time the same thing, tight when wet and loose dry.     

    after i while i found this article,  its the same problem i encountered with pictures 

    http://dianamosesbotkin.blogspot.no/2013/10/pva-horror-tale.html?m=1  


    i read that professional canvas maker like cleassens of belgium use acrylic glue to their canvases and coating both sides, is this a better option?   can you dilute pva with something other than water?

    I know about the Golden products but now i ended up with having alot of PVA and trying to make it work.     




     

        

  • Question asked 2017-11-18 16:16:32 ... Most recent comment 2017-11-25 08:49:15
    Paint Additives Paint Mediums
    Question

    ​I usse oil glazes over a monochromatic egg tempera underpainting.tand Oil (1part Sstand Oil and 6 parts english turpentine) is not satisfactory. Normally my woerk requires 3- to 40 very, very thin oil glazes. Can you recommend a workable reciepe? Alklyd and other such "synthetic materials" are not satisfactory for me.

  • Question asked 2017-11-11 11:19:05 ... Most recent comment 2017-11-20 22:07:03
    Oil Paint Varnishes
    Question

    What did the old masters use to paint whisker thin long lines with oils? I have seen work by several Dutch masters but also the French Academics like Jerome and company who were able to manipulate paint and produce incredible details in a miniature scale, as if they were using a micron pen loaded with paint. I am trying to keep it simple, and I don't want to get into resins or magic media. I have found so far the best combo is to paint over a couch of linseed oil with paint + stand oil. The best brush so far is the size 0 spectre by W&N, but I am sure that are better brushes out there that work best for this purpose.  I know from trying that a lot of the success is in the manipulation of the paint and having a steady hand.  Correcting the shape of the paint with another paint, working in layers. Smaller brushes may produce better results + practice.  I am able and have produced similar details in my still lifes but the scale is not the same. It gets to a point where the detail is so small that I am not able to do in oils.  But if it is a resin, which one would you use.  My friend uses Amber from Donald Fels and Venice turps by Kremer pigments. Thank you.

  • Question asked 2017-11-19 11:16:06 ... Most recent comment 2017-11-20 13:57:41
    Paint Mediums
    Question

    ​ I was trained in a 15th century glazing technique that tries to mimick the process of the Van Eyck brothers. Sir Charles Eastlake alongside with the technical bulletins from the National Gallery mentíon the usage of resins in their mediums. The National Gallery bulletin particularly mentions pine resin, not just for the Van Eyck brothers but also for later flemish painters like Rubens and Van Dyck. Do you happen to know specifically what pine resin is? I currently use dammar but i'm not sure what pine resin actually is.

  • Question asked 2017-10-25 10:54:17 ... Most recent comment 2017-11-18 12:35:57
    Flexible Supports Oil Paint
    Question

    ​I've read that cotton canvas shouldn't be stretched at larger sizes for oil because it's too flexible, but that a heavier cotton can make up for what it lacks in strength. How does 15oz cotton compare to linen at sizes 8ft and above?

    Thanks!

  • Question asked 2017-04-25 14:20:23 ... Most recent comment 2017-11-18 12:30:08
    Paint Additives Oil Paint Paint Mediums Scientific Analysis Art Conservation Topics
    Question

    I have a query regarding the section in the MITRA documentation on Solvents about Clove Oil for Oil painting:

    "Essential Oil of Cloves or Clove Oil has been used as a preservative in emulsions and as an additive to mediums to substantially slow down their drying rate. There are far better preservatives available today. The use of clove oil as a drying retarder is greatly discouraged as its addition tends to substantially weaken the dried paint film.

    Other Essential Oils and Extracts are also periodically used in art making. Oil of rosemary sometimes served as a substitute for clove oil and as a component in the creation of complex oil-hard resin mediums. Like clove oil, artists should forgo the use of these materials as their dangers far outweigh and perceived benefits."

    I and many other painters I know use Clove Oil to extend the drying time and I have never read anything negative about using it before.

    Please can you tell me what evidence led to the conclusion that clove oil weakened dried paint film.

    What were the numbers for the control, clove and rosemary in the studies that were done?

  • Question asked 2017-11-16 13:20:58 ... Most recent comment 2017-11-16 15:45:16
    Rigid Supports
    Question

    Is it true that the hardboard used for the museum grade clayboard used for scratchboard is acid-free? Do I need to worry about outgassing? When I painted an "X" across the back to help prevent warpage, the Golden Titanium White acrylic paint immediately turned yellowish in hue. Why? As a precaution, should I coat the sides and back with GAC 100+500 (since it's chily in the house)?​

  • Question asked 2017-11-15 19:19:37 ... Most recent comment 2017-11-16 12:26:50
    Acrylic Rigid Supports Oil Paint
    Question

    ​This question is directed mainly at Sarah Sands (though anyone can feel free to weigh in): 

    Are there any particular concerns with using GAC 200 to seal the back and sides of unbraced Hardbord panels? I've tested a lot of different finishes for this purpose, and consistently find that GAC 200 performs better than just about anything else in this role. My criteria are two-fold: I'm looking for a coating that will provide some moisture resistance, and also one that will act as a sort of consolidant to strengthen the Hardbord (particularly the edges, which when damaged are prone to fraying). 

    Strengthening the Hardbord is probably the most important concern for me; in general, I don't find Hardbord to be all that reactive to humidity changes, but it can be vulnerable to physical damage, especially when dropped. With a couple of coats of GAC 200 on the back and sides, it seems much more durable. The cured GAC makes the edges very hard and, well, solid. I can drop a panel from eye level onto a hard floor--on a corner!--and it suffers no visible damage. An unsealed panel dropped in the same manner invariably ends up with a dented corner that imediately starts to fray. 

    The fact that the GAC dries relatively quickly is also a plus. I've gotten similar results with oil-based polyurethanes, but they require at least four coats to build to a film on Hardbord (which is very absorbent), and so drying time becomes an issue. Being able to seal the back of a panel in a day (rather than several) is helpful. I've also tried GAC 100, but it dries to a somewhat tacky surface, and does not harden the edges of the panel to the same degree that GAC 200 does. I know that GAC 200 is supposed to be more brittle, but it held up well to my impact tests. 

    So I guess the question is whether or not this is an acceptable use for GAC 200. Also, will it remain stable as a surface coating on the back and sides of a Hardbord panel, or should I top-coat it with something else?

  • Question asked 2017-11-08 11:25:44 ... Most recent comment 2017-11-08 15:11:26
    Oil Paint Rigid Supports Grounds / Priming
    Question

    ​I've searched here on the topic, and also read the "rigid supports" document in Resources (which is a wonderful reference), but I have a few additional questions about working on copper. 

    1. I'm using relatively thick copper (14-gauge etching plates) and working fairly small (maybe 11x14" or so, down to 5x7"). Is it necessary to brace supports of this size, or would it be sufficient to put a lightweight (floating) backing board behind the plate in the frame--perhaps Gatorfoam, or a layer or two of museum board? 

    2. My process to prepare the surface of the plate: degrease with denatured alcohol, thoroughly abrade the surface with sandpaper or steel wool (with the aim of completely stripping the surface to expose fresh metal), vacuum off any copper dust, then degrease again, making sure that all dust and residue gets removed. Then allow to dry, and prime. Does that sound about right?

    3. How about where the copper is not covered by primer/paint? Like the back and sides? Can I just let that oxidize, or should I seal it with something? Renaissance Wax, maybe? 

    4. I assume any oil-based primer will work? How about an alkyd primer, like Winsor & Newton's Oil Primer? I have a few small test sheets on which I tested some straight lead carbonate in linseed oil (RGH), a lead painting primer that contains some titanium white and driers (Rublev), and the Winsor & Newton primer. All three dried very quickly (the W&N primer was touch dry in a matter of hours). I'm guessing that the copper is a drying catalyst? The Rublev primer turned very green upon drying; I don't think that it was a matter of surface prep, because the RGH lead primer is right next to it on the same sheet of copper, and it didn't change color at all. The Winsor & Newton primer took on a slight green tint, but it's barely noticeable. Is this sort of thing common? Something to worry about? I don't think I'd use the Rublev primer, since the color change in that case was considerable. 

    5. I skipped the oft-recommended garlic step, just on the basis that I have been able to find a consistent or empirically supported reason for its use. Some sources say that it helps to "etch" the metal (though it is unclear how, since garlic is not acidic). Some sources say that it might serve as a wetting agent (which makes more sense, except for the fact that copper doesn't seem to need a wetting agent--it takes oil paint really well, with no beading). Some sources say that it helps the paint bind to the surface chemically, rather than just mechanically, but I don't think that's correct. Don't oil films exchange ions with copper? In any event, the idea of putting an aqueous paste between the metal and primer seems like a bad one to me, but perhaps there is a purpose for this step that I haven't considered?

    Thanks!


    -Ben



  • Question asked 2017-11-06 14:54:53 ... Most recent comment 2017-11-07 20:05:12
    Drying Oils Varnishes Oil Paint
    Question

    ​Could you please talk a little about the practice of using isolating varnishes between layers of paint?
    Personally I don't do it, but some advocate it so it would be good to have some authoritive documentation to refer to.

  • Question asked 2017-11-02 15:35:27 ... Most recent comment 2017-11-03 18:10:01
    Art Conservation Topics Gouache Matting, Framing, and Glazing Studio Tools and Tips Varnishes Watercolor
    Question

    ​Hello MITRA folks...Would you speak to the issues from a conservator's point of view (especially concerning long-term cleaning, repair and UV protection) for the growing trend to varnish, wax and resin-coat finished watercolors as ways to avoid the cost and biases against "works under glass?" Your perspectives are much appreciated.

  • Question asked 2017-10-28 15:55:13 ... Most recent comment 2017-10-30 10:11:35
    Art Conservation Topics Other Scientific Analysis
    Question

    Hello, im a MA student currently working on some research projects. I would like to ask you for some advice (if this is not the place just tell me).

    One of the research im beggining with is about 'new digital technology uses in conservation of art' (3D scanning, ink-jet transfer reintegration, 3D reproductions, etc) . I was looking in to related bibliography or other information but there is not much of it, so I would be gradefull if you suggest some information or examples of new digital technology used in conservation, or if you know any book or institution (i.e. factum-arte) regarding this topic.

    Thank you.

  • Question asked 2017-09-27 15:45:45 ... Most recent comment 2017-10-28 16:40:30
    Photo-Documentation / Digital Printing Pigments Technical Art History
    Question

    An interesting question for you!

    ​I would like to do a reproduction of one of my favourite paintings, Vermeer's 'Girl with a Pearl Earring'.

    I have found the excellent close up scanned image that the Mauritshuis have in their collection:
    https://www.mauritshuis.nl/en/discover/mauritshuis/masterpieces-from-the-mauritshuis/girl-with-a-pearl-earring-670/

    I can see that there is a lot more detail in the darks than I've seen in other images. However I understood that the blue of the turban was made with natural Ultramarine and Lead White, yet the blue in the turban looks a little blue green to me, rather than blue red.

    Other images I've seen have the painting with more of a blue-red cast on the turban and on other parts of the painting: 
    https://upload.wikimedia.org/wikipedia/commons/6/66/Johannes_Vermeer_%281632-1675%29_-_The_Girl_With_The_Pearl_Earring_%281665%29.jpg

    I was wondering if any of you knew if the colours in the real painting are more accurately shown in the mauritshuis scan, or in the second link from wikimedia.

    Thank you!
    Richard

  • Question asked 2017-10-24 16:52:44 ... Most recent comment 2017-10-25 15:51:53
    Drying Oils
    Question

    ​I have always worked under the stricture that linseed oil based paints and mediums, with at least some lead white in the paint layer, produced the the toughest, most flexible paint layer possible.

    However, considering that I work on rigid panel, not on stretched linen when this advice was likely first made... 

    Q #1  Would it be adviseable to switch to safflower or walnut based oils and mediums instead, considering that they yellow less, or at least more slowly?

    Q #2  How important is a flexible paint layer on a rigid support?


    For people who are concerned with the slower drying rate of safflower and walnut, I have found that the slower drying rate can be mitigated by placing the painting into an enclosure with incandescent bulbs, which will bring the temperature up to F 90-100.

    Q #3   Do you see any problems with placing the wet paintings in a warmer environment for more rapid drying?   


    No added driers are needed. 


    Thanks for your thoughts.  

  • Question asked 2017-10-24 17:05:07 ... Most recent comment 2017-10-25 14:46:59
    Grounds / Priming Rigid Supports
    Question

    ​Q #1   Are there any advantages to oil primers over acrylic dispersion ones for creating the best adhesion to the paint layer on a rigid support?

    The oil primer, I suspect, would create both a mechanical  and chemical adhesion to the paint layer, whereas the acrylic dispersion primer would create only a mechanical one...or is the mechanical adhesion great enough that it would easily suffice on a rigid panel?


    Q #2  If using oil primers on rigid panels, would the primer need to cure for several months to a year before using?

    Information in your "Resource" section suggested that the dried primer merely needed to resist the fingernail before using.


    Thanks for your thoughts.

  • Question asked 2017-10-14 15:13:18 ... Most recent comment 2017-10-25 13:33:58
    Oil Paint
    Question

    ​Is Arches Oil Paper an acceptable support for an oil painting with a long life? Alternatively, do we know what makes this oil ready, in a way that is different enough from what you usually call paper, which is not oil ready due to the rot attack of oil to the paper fiber? (Perhaps this paper is a synthetic polymer?) I am aware of some other common problems associated with painting on non rigid supports, but am interested in using marouflage techniques to adhere to panels for greater stability. Is adhesion of paint on paper-in general- for impasto technique problematic?

    If oil was the medium usually used for hand touching photos, do these have acidic oil rotting issues?


    Sorry for the host of inquiry, I am a curious person:) Thanks for any ingith into the oil paper etc.

  • Question asked 2017-10-23 13:29:21 ... Most recent comment 2017-10-24 00:17:23
    Technical Art History
    Question

    ​I have studied art materials off and on since 1990 and own copies of several of A. P. Laurie's books and those of D.V. Thompson, Ralph Mayer, Cennino Cennini, etc.   I am still interested in the historical development of art materials and practices over the centuries but do not take them seriously as sound, modern studio art practices.   No search for the elusive "secret mediums" of the old master here.

    Q #1   Except as a study of the history of art conservation/art materials, how useful are these books to the art student wishing to use the most permanent materials and practices?  


    So many of the materials discussed are either discontinued, replaced with more permanent ones, changed in chemical composition but with the same name, etc,  or altogether unavailable, that it seems as if it would only serve to confuse the new artist.   I know that it did years ago when I first started studying them and my mind often swam with conflicting advice.  


    Q #2   With more recent research and knowledge of art conservation and materials, how far back can we depend on books on art materials and practices?   20 years, 40 years, more?


    Q #3   Ralph Mayer died ca 1980, so how reliable are updates to his books?


    Its a shame that we do not have more authors who are well versed in chemistry to help with the technical aspects like A.P.Laurie but The Artist's Assistant , by Leslie Carlyle, Archetype Publications, 2001, while not a painting methods book, has a lot of useful, modern  information on many older practices and art materials.


    Thanks for your thoughts.



  • Question asked 2017-10-05 20:11:57 ... Most recent comment 2017-10-19 11:47:31
    Oil Paint Other Paint Additives Paint Making Scientific Analysis Studio Tools and Tips Technical Art History
    Question

    I am in the copyist program at The Met, copying The Flight into Egypt by Tanner, link below:

    https://www.metmuseum.org/art/collection/search/16947 

    In searching for more information about Tanner's techniques, I came across this 2011 presentation:

    https://www.youtube.com/watch?v=hWxErF_nzd4

    My questions are specifically about the content from 33:20-34:46. 

    I'm trying to figure out two key techniques. First- the dragged paint technique. Brian Baade mentioned this briefly in the presentation for the Near East Scene-Mosque in Tangier painting. In trying to achieve the same effect, I can't seem to get my paint to break. I buy my pigments, not make my own. Do commercial pigments come with too much oil? Is there some way of getting a dryer paint? Second- the impasto texture of the paint in The Good Shepherd. Brian Baade mentions that he doesn't know what method was used to apply paint, but I thought I'd ask about what tools/techniques were found to produce the most similar result.

    Thanks,

    Karri

  • Question asked 2017-10-16 16:16:57 ... Most recent comment 2017-10-17 13:11:47
    Varnishes Oil Paint
    Question

    ​I want to do a painting (on canvas or on acrylic-gessoed paper) in charcoal and oil but I'm unsure how to "fix" it or varnish it.  I love charcoal and usually just use it for the sketch underneath the oil and then paint over it but what happens if I do a painting that has a combination of areas with only charcoal on it, some areas that are paint only, some areas that are paint and charcoal together, and some areas with charcoal over the paint? The oil would be very thinly applied. Would I use a spray varnish at the end to "fix" it because a brushed-on varnish would lift the charcoal? If on paper, should I frame it with a good space between the glass and artwork? If y'all think that charcoal and acrylic paint would be better for this type of art, what would I use in that case to seal it? Thank you for this helpful site. 

  • Question asked 2017-10-13 10:35:14 ... Most recent comment 2017-10-13 12:06:29
    Pigments
    Question

    Do you have an exact recipe for extracting Fra Angelico blue from lapis lazuli? A student of mine needs the recipe for his conservation degree, but his professor also wants more scientific quantities. Cennino cennini's recipe for natural ultramarine is too vague for their MA classroom. Ex: how strong should the lye solution be and it's ideal ph? How much ashes to water? How much lazuli to resin, wax and oil? Etc. Thanks

  • Question asked 2017-10-11 21:18:05 ... Most recent comment 2017-10-12 21:52:33
    Grounds / Priming Oil Paint Studio Tools and Tips
    Question

    ​🍁 Fall Greetings, MITRA folks ~ Can you tell me if there is any technical reason to NOT paint light-to-dark in thin layers of oil with an alkyd walnut medium over a thin Titanium White (no Zinc) first layer on the acrylic gessoed surface? 'Durable' is my concern. Any thoughts would be much appreciated. 🍂

  • Question asked 2017-10-12 15:58:50 ... Most recent comment 2017-10-12 20:22:58
    Flexible Supports
    Question

    Is it safe to wash unused canvas in the washing machine? If not, can it be washed by hand? I came across a lot of 15 oz. cotton but it has some dirt in spots and deep creases that can't be ironed out.


  • Question asked 2017-10-10 15:33:41 ... Most recent comment 2017-10-12 11:55:38
    Egg Tempera
    Question

    ​My understanding was that Andrew Wyeth used a traditional chalk and glue gesso, learned from his brother-in-law Peter Hurd, under his egg temperas paintings.  I presumed this from various articles I've read; also from a Mr. McNeil (I think his name was), an older gent (he was in his 90s when I met him 20 years ago) who used to run a company called Permacolors and told me he made traditional chalk and glue gesso panels for "Andy".   However someone else recently told that Wyeth worked on caesin gesso. Can Dr. Joyce Stoner (or anyone who knows) corroborate what ground Wyeth worked on?  

    Thanks,  Koo Schadler

  • Question asked 2017-10-10 12:35:23 ... Most recent comment 2017-10-11 17:51:41
    Egg Tempera
    Question

    ​​Many years ago I bought a product called Disponil from, I think, Kremer Pigment in NYC - it worked great at combining hard to wet pigments with water.  I haven't been able to find Disponil again.  I now use Golden Paint's Universal Dispersant.  Am I safe in presuming that the Golden's product is compatible with egg tempera (for pigments that resist wetting)?  Any other comments on dispersants and egg tempera?  

  • Question asked 2017-10-10 11:04:40 ... Most recent comment 2017-10-10 18:26:00
    Acrylic
    Question

    ​I've heard that  a little 4F pumice, added to  acrylic primer, creates a smooth oil painting surface on rigid panels but with a little more tooth to grab onto the paint.   Acrylic primer alone seems a little slick for me, but I do not necessarily need great absorbancy.  

    Any problems?

    Would this surface be too abrasive for bristle or sable brushes?

    Would the pumice increase absobancy? 

    Thanks for your thoughts.

  • Question asked 2017-10-10 11:46:05 ... Most recent comment 2017-10-10 16:39:02
    Flexible Supports
    Question

    ​Do you see any delamination or other problems with oil paintings made  directly on PVA sized, 140 lb, cotton wc paper, rather than on an acrylic primed paper?


    I've been using sized, 140 lb,  cotton wc paper for oil studies and small paintings for for 18 years without problem.   The paper has a texture that I enjoy and I size them on one side with 2 coats pH neutral PVA size, (75% water-25% PVA glue), as suggested by Robert Gamblin.   The size is allowed to dry in between coats. 

    I do not apply an oil or acrylic primer as it tends to smooth the very texture that I like and I can collect hundreds of small plein air studies and sketches on paper, for reference, without the massive weight and volume that mounting on hardboard or dibond would entail.   The paper is stiffer than the same on unstretched linen so that studies can be more easily be handled.

    On occaision, I mount them on panel for sale.   Again, no problem in the years that I have had paintings on paper mounted on panel, but I thought that I would check with you anyway.    

    I realize that the primer would likely be more absorbent and may create a better mechanical bond with the paint layer, but I've seen so many plein air studies of 18th - 19th C masters painted and/or mounted on a lot worse supports and often without sizing.

  • Question asked 2017-10-08 04:40:02 ... Most recent comment 2017-10-10 15:50:19
    Grounds / Priming
    Question

    ​Dear Moderator

    I am trying to find a way of working that produces the best possible combination of characteristics for my way of working I currently have a thin linen which I want to adhere to panel once I do a decent painting on it Because it's fairly thin it's not taking the acrylic size well despite using a good acrylic matte medium in two coats which I've previously tested and used without problems With this linen however I'm getting strikethrough of oil paint on tests I've made Consequently I thought I'd try sizing it with the same medium then applying a couple of layers of good quality acrylic primer to prevent this strikethrough and then a final coat or two of my preferred lead oil primer Does this seem a reasonably sound given that ultimately it will be adhered to a panel? PS sorry most of my punctuation keys are refusing to work! 



  • Question asked 2017-10-06 19:28:03 ... Most recent comment 2017-10-06 22:12:49
    Sizes and Adhesives
    Question

    Dear Moderator. I am trying to find a way to get a smoother surface for portrait painting in oils as I'm regularly encountering lumps and bumps in my lead oil primed linen. I've tried gently abrading the raw linen, pre sizing,  with a pumice stone, which did help, but now find the acrylic size I've applied is quite rough to the touch. I'm using Liquitex matte medium diluted 1:1 with water and plan to apply 2 coats. I know about the need for a size to penetrate the fabric rather than act as a distinct layer. I'm not trying to achaieve a glassy surface just a smooth one. By the way, I intend to glue the painting to a panel once it's finished. I'm concerned that using sandpaper or pumice stone on the size will actually remove the size to the point hat it no longer performs its function of sealing the canvas. Is this a legitimate concern and if so what can I do about it?  

  • Question asked 2017-10-06 11:18:16 ... Most recent comment 2017-10-06 13:00:52
    Rigid Supports
    Question

    ​Hello, 

    I found a great source for copper supports and am familiar with how to prepare them.  I was curious though, as metal supports become a bit more pliable at larger sizes, what sort of glue would be recommended for mounting them?  I wouldnt want one to get accidentally dented from the front or back once framed and finished

    If mounting to wood, should I glue 100% of the surface to take into account the woods hygroscopy?  Or would it be better to 'hang' the mounting from the top, as one would when framing a drawing? I imagine it would be an easier process to mount to ACM panel.

  • Question asked 2017-10-06 11:37:19 ... Most recent comment 2017-10-06 12:17:19
    Varnishes Ink Oil Paint
    Question

    I have an oil painting that was signed in ink.  the written text was done with a micron colorfast brush pen/marker (recommended by one of the conservators here).  

    It is now time to varnish that painting, just got it back, though completed in 2014.  I usually use regalrez (gamvar) to varnish these days- though I am slightly concerned that brushing over the ink portion will cause it to run/bleed?  I would like to make sure to varnish over the signature to protect it as well.

    My current plan is to put a light aerosol spray varnish over the part in ink, perhaps two lightly sprayed coats, and let it cure for a couple of days before brushing varnish over the entire picture.  How does that sound to the mods here?  

  • Question asked 2017-10-01 21:45:08 ... Most recent comment 2017-10-05 19:49:39
    Flexible Supports
    Question
    My paintings tend to be larger (7',8',9') and can be quite fragile. To help protect them, I have typically stretched the unprimed canvas over a cradled wood panel. My first question is whether or not this is actually beneficial, or whether the panel is unnecessary? The canvas rests over the wooden panel but is not glued down.

    Recently I've been considering going back to stretcher bars (probably aluminum) and inserting a lightweight foam into the stretchers attached only to the cross bars, so the perimeter could still be stretched if necessary. My second question is whether or not this is a more permanent solution?

    I do not have access to gator board, because I can't  find single sheets and the shipping is outrageously pricey. I do have access to foam core and 1/2" and 1" sturdy construction insulation foam (which seems more rigid and doesn't have a paper veneer).  My third question is whether foam core or the construction foam is worth using/and or dangerous in terms of off gassing etc. to the back of the canvas? 

    My fourth question would be if you all have any better solution/suggestions I hadn't considered.

    Thanks!
  • Question asked 2017-09-27 14:12:45 ... Most recent comment 2017-09-28 16:50:52
    Rigid Supports
    Question

    I would like to mount some 10" x 20", oil studies on pH neutral PVA sized, 140 lb wc paper, onto 4 mm dibond using acrylic dispersion medium.   I suspect that this is not optimal, but wish to frame the studies.

    Will a water based "adhesive", such as acrylic dipersion medium, take hold of a roughened, non absorbent, dibond surface?

    Am I headed for trouble?

    Have done the same on gatorfoam, in  smaller sizes, without problem in the past.   The wc paper is stiffer than linen and doesn't seem to buckle or bubble in these small sizes, unlike linen.

    Read the pertinent posts and information in the resources section, but it did not specifically address finished oil studies, on paper, being mounted onto dibond, hence the above question.   

    As dibond is not absorbant, coating both sides of the panel should not be necessary, correct?

    Thanks for your help.

  • Question asked 2017-09-13 05:33:23 ... Most recent comment 2017-09-26 23:14:56
    Alkyd Drying Oils Grounds / Priming Industrial and Non-Traditional Products Paint Mediums Oil Paint Solvents and Thinners Rigid Supports Scientific Analysis Varnishes
    Question

    Hello MITRA,

    I might win the prize for bringing the most problematic query to the forum. The reason being that my methods of using oil paint are unorthodox, and I don't have the most scientific of minds. But please don't be too hasty to judge my methods. I have spent years of time and money getting to the point I have, and I am approaching you now seeking a little reassurance/guidance, but also knowing that you may not be able to give it.

    Where to begin. Essentially, I dilute oil paint to the extent of being able to pour apply it (alarm bells ringing already, I know). I mix oil paint in different concentrations, with a combination of solvent and medium, that when poured onto a flat laid rigid support (these days a primed Aluminium Composite board), they interact and react against each other in desirable and unpredictable ways as they meet and combine- natural forms, even fractal patterns, appear within the very dilute paint. detail.jpg Once this layer is dry, after a few weeks, I paint glazes on top in a more controlled manner. 

    What I seek in pouring oils, is a contradiction really: Stable instability.

    I know the basics...that if you just dilute oil paint with solvent it can't bind properly and will chalk off.. so I've alwyas been careful to add oil/alkyd medium of some kind. I also know the fat over lean rule. But when I am throwing it all on together in one liquid layer- I can't really apply it that rule in the same way... 

    The first year I was making paintings like this I used just solutions made of Turpentine and Linseed Oil, but I encountered drying and yellowing problems which I since have understood… I then adapted my method and started using drying mediums instead of linseed oil.

    The main successful recipe I have used is:

    - Liquin mixed with Zest it solvent, and Oil paint.

    I think and hope I am using enough of each, for the paint to be just strong enough to cure and not peel off. It has has made many successful dry and even paintings over the last 3 years. It gives a very thin, flat surface, almost like watercolour, once dry. It has had and almost enamel surface which succesffully took glaze on top. But I do find that it has sunk in significantly since I changed primer to Thixtropic alkyd primer (which i thought would be better on Aluminium panels) but I have read that some primers make sinking in worse.  I used to use an oil primer, which I think I will return to. 

    Q: Does it matter if a painting surface is sunk in... if I don't mind the look of it being uneven? Is the worry that any varnish will bond with the paint and not be able to be removed? – does this even matter? Can I use a few thin coats of spray retouching varnish to seal it and then later a proper varnish on top? Would that top layer of varnish be able to be removed if I did that? Is there a big danger of the painting yellowing /darkening a lot like this, even if I use thin layers of spray varnish? (winsor and newton).

    The only problem with the Liquin is that it darkens over time, and actually has over quite a short period of time in recent paintings: compare detail (liquin) early 2017.jpg with detail (liquin) late 2017.jpg . I don't mind how it has changed and darkened.. but I would like to know if you think it will continue to darken more and more..

     Because of this darkening issue, but still wanting to avoid yellowing oil.. The second and most recent recipe I am trying is :

    -'Drying Poppy Oil' with Zest it solvent and the oil paint. 

    I have started experimenting with this because poppy oil is supposed to be good for pale colours… and I use a lot of white, very pale and muted colour fields. (which is another issue.. finding the best white for using large amounts..currently using Permalba Original. But thinking of trying lead white?! As if I hadn't already made like hard enough for myself!). drying poppy oil detail.jpg  I knew poppy oil itself would be far too slow drying for what I do, but thought the one with driers added to it might work? The early stages of the experiment and I have managed to achieve a dry and even surface.. glossier than the liquin ones. But I have yet to try painting glazes on top of this layer. Q: I have heard that poppy oil is more likely to crack, is this true also of drying poppy oil? In which case, would you say the surface I have now that seems smooth and slippery, will eventually crack over time?

    So there you have it.

    I don't know of any oil painters historically to employ methods like these, I do know artists that have done this kind of thing using Acrylic or resins. I can only find one other artist online that claims to be using a similar technique in oil: 

    https://mauricesapiro.com/viscosity-series-poured-paintings/

    But other than his comparative technique, I have not found any other information to help me navigate this process. I suspect that would be because it is unadvised to be diluting and pouring oil paint in such a way for all the potential instabilities it causes..  But it is partly the instability that makes me want to paint in this way in the first place! You see the dilemma!

    I am happy with the paintings currently as they are.. in the short term, they seem stable. But I am concerned with the long term. I would obviously like to avoid Extreme yellowing and and peeling off of any paintings in the future! It is not the end of the world if they change and crack a little bit. But if it is going to be a lot, then I would feel unethical in selling the works. OR I do you think I should include a clause when selling that says I can not vouch for the archival quality of the work?

    I am aware that what I am trying to achieve would be probably be far easier and perhaps more straightforward if I used acrylics instead- (it would sure be a lot cheaper!)… but I am not quite ready to give up on the beautiful effects I can achieve using oil paint, everything I have invested in experimenting. 

    Any tips, or even educated guesses, on ways I could be doing this better - mediums that are good for making a strong but pourable paint film?! Ratios I should keep to? or other ways to keep the work stable for as long as possible... would be greatly appreciated. Thank you! sorry this has been such a long and confused essay...

     

  • Question asked 2017-09-26 13:51:45 ... Most recent comment 2017-09-26 17:59:21
    Rigid Supports Paint Mediums
    Question

    ​I have been warned about the dangers of using Resins in mediums.  My understanding is that the issue is twofold:  on is in cracking of the paint layer itself ( possibly yellowing as well) and then also in conservation as the removal of the resinous varnish layer would also affect/remove a portion of the paint layer.  
     I want to be very specific to the Resin and meidum that I use becuase  the answer may not apply to all resins and mediums equally.   I use 2 parts sun-thickened linseed oil, 1 part turpentine and 1 part Canada Balsam.
     I have a number of questions. 1. With respect to yellowing, would that not be mitigated by the varnish layer which would protect the paint. If the varnish yellows, it can be removed and a fresh varnish put on, so that yellowing is not an issue for the paint layers themselves?
    2.  To what degree is the cracking attributed to the rigidity of the painting surface and to what degree the resin in the medium?  Are the caveats for using Canada Balsam in the medium significantly reduced is the painting surface is a stable one?  Many thanks.



  • Question asked 2017-04-30 18:12:23 ... Most recent comment 2017-09-25 21:21:15
    Acrylic Health and Safety Paint Additives
    Question

    I am exploring the technique of acrylic pouring / flow acrylic / liquid acrylic art, and am looking for suggestions on cell creation. Many of the artists I have found online share assorted techniques such as using a silicone additive or floetrol, often in addition to using a heat torch of some kind. (A good reference would be the YouTuber Annemarie Ridderhof.)

    My question is this: is there an additive or process that I can use in place of some of the above additives, that are odorless (I have medical complications that make me very sensitive to smells) and are safe to be used? I fear that applying direct heat to acrylic and whatever additives being used, can potentially cause fumes with dangerous effects.

    For context, I generally use basic liquitex student grade acrylic paint with water on assorted sizes of stretched canvas.

    Many thanks in advanced for any tips or suggestions!


  • Question asked 2017-09-19 19:10:46 ... Most recent comment 2017-09-20 16:11:02
    Egg Tempera
    Question

    I'm planning some paintings in tempera grassa.  I've worked before in the medium, using an emulsion of egg yolk and sun-thickened linseed, almost equal parts each but a bit more yolk so it's water-soluble. The paint had good working properties, but I'd like a bit more hardness and shine, as one would get by adding dammar (which many tempera grassa recipes call for) but which I don't want to add (because of the negative attributes of dammar).  Is there another resin I could incorporate for a similar affect?  Would any of the modern synthetic resins be a possibility?

    Thanks,

    Koo Schadler

  • Question asked 2017-09-19 15:24:31 ... Most recent comment 2017-09-19 21:34:59
    Oil Paint Sizes and Adhesives Rigid Supports
    Question

    ​I've mentioned this in another thread, but haven't actually phrased it as a question, and I am curious what the MITRA folks think about using a thin sizing of Paraloid B-72 to reduce the absorbency of either Claybord or traditional gesso, prior to painting with oils. I mean, I know that it works, from a process standpoint, but is it a sound practice? 

    My own research on Paraloid B-72 suggests that it is one of the more stable synthetic resins and is not prone to yellowing, but like all acrylics, it is somewhat sensitive to solvents. Then again, it's incorporated into the ground (which in the case of Claybord, already contains acrylic resin), so is it really any worse than painting on an acrylic primer? 

  • Question asked 2017-08-30 05:17:59 ... Most recent comment 2017-09-18 15:37:19
    Pigments
    Question

    ​As some of you work for (or have close links with artist paint companies), I wonder if you were aware of any new paint pigments that are being tested by paint manufacturers at the moment? :)

  • Question asked 2017-09-16 10:41:07 ... Most recent comment 2017-09-18 11:34:42
    Acrylic
    Question

    ​Hello,

    I like using copper panels with oil paint. Do you know if copper panels and acrylic paint are compatible as well?

    Thank you

  • Question asked 2017-09-09 22:42:34 ... Most recent comment 2017-09-18 09:57:01
    Flexible Supports Grounds / Priming Oil Paint Sizes and Adhesives
    Question

    ​The store-bought stretched heavyweight canvases that I've used before have, it turns out, no sizing underneath their three factory-applied acrylic gesso layers. I am concerned about oil paint strike-through, and wonder if two (or more) additional layers of high-quality acrylic gesso would insure the canvas durability? I've read somewhere that acrylic gesso, being formulated for absorbancy, will always remain susceptible to oil strike-through. I'd love to hear your professional thoughts on the subject. Also, would you explain materials and technique for attaching a rigid covering to protect the back of a stretched canvas? Thank you so much.

  • Question asked 2017-09-14 09:41:01 ... Most recent comment 2017-09-14 19:35:53
    Art Conservation Topics Flexible Supports Grounds / Priming Oil Paint Pigments
    Question

    I've read all of the references here regarding Zinc White (PW4), and it seems that the current opinion is that it is best to avoid all applications of Zinc White (PW4) for oil painting due to durability issues, at least until further clarification from new research studies is available. Am I understanding correctly? Thank you for the clarification. Susan

  • Question asked 2017-09-05 18:12:26 ... Most recent comment 2017-09-11 15:15:23
    Acrylic Oil Paint Rigid Supports Industrial and Non-Traditional Products
    Question

    I have read that Polyethylene terephthalate is a good support for painting with acrylics, and decided to try painting on the sheet version of it. However, there are different variants of plastic sold under the general name "PET". I can buy:

    • APET (amorphous PET)
    • PETG (Polyethylene terephthalate glycol-modified)​
    • other variants with additions that claim to enhance UV-resistance, etc.

    My question is: are all of these equally fine as painting substrates? From what I've read, the glycol-modified version doesn't become hazy or brittle when heat-treated, but I don't know what type of heat would be required to be relevant for painting. Also, I'm not sure whether any of them would be more likely to leach anything (glycol?), or be more susceptible to propylene glycol present in paints.

    As a side question: is sheet PET compatible with oil paints?

  • Question asked 2017-09-06 18:35:00 ... Most recent comment 2017-09-06 19:12:08
    Oil Paint Paint Making Pigments
    Question

    ​Hi, I recently purchased some azurite pigment and I want to mull it into paint, I have never done this, It is my first time and I am wondering what is the right way to do it? should I wet the pigment first in water, or should I just add oil to the dry pigment. Also what oil is recomended with azurite

  • Question asked 2017-09-05 11:13:55 ... Most recent comment 2017-09-06 13:28:23
    Varnishes
    Question

    ​Daer MITRA 

    I have a painting that I finished recently which I wish to photograph for online entry to a competition. I had a fair bit of sinking in which I've tried to correct with oiling out, with reasonable results but there is still a certain dullness I would like to correct. I am planning to apply a good quality retouch varnish as a temporary varnish to my touch-dry painting as I feel it will bring out the colours etc. I couldn't find much information about using retouch varnish in this way (i.e. as a temporary varnish) in the resources section of MITRA. Apart from careful application technique etc, which I can read about here or in my Gottsegan book, is there anything I need to know or any reason to avoid retouch varnish? 

  • Question asked 2017-08-21 04:03:00 ... Most recent comment 2017-09-05 10:16:48
    Oil Paint
    Question

    ​Dear MiTRA person

    I recently purchased some oil paints by a reputable German manufacturer who sadly is not explicit about the oils used as binder. They admit to using a combination of oils but the feeling on online forums is that there is probably a preponderance of safflower or perhaps even sunflower oil. I have some concerns about using them because inevitably they must have added some driers and I am given to understand that some metallic driers like manganese can cause darkening in the paint film over time.  As is noted here in the resources articles, most paint manufacturers do add driers to one degree or another but the devil is of course in the detail ie how much? I've emailed them to enquire as to whether they have done any testing or have any reassuring information on this front but the response was a bit confusing as they kept directing me to information regarding the lightfastness of these paints. (And by the way they use the Blue Wool scale to assess lightfastness which as far as I know is very outdated!). Do I need to be concerned regarding darkening when using paints of this type? 

  • Question asked 2017-08-03 15:19:27 ... Most recent comment 2017-09-04 17:19:32
    Oil Paint Drying Oils Paint Mediums
    Question

    Dear MITRA,

    I encounter a lot of sinking-in due to the large fields of dark colors I use. I’ve been oiling out with straight walnut oil as a final layer in some cases despite the warnings for several reasons: 1) The brushwork is sucessful and seems a shame to repaint. 2) I don't have six months to wait for varnishing. 3) Even when I do oil out, then reapint, I often get more sinking it. 4) It solves the problem in the short term.

    I have read all of the posts relating to this topic (which have given me some good advise about other ways to mitigate the probelm) but still have several quesitons–

    If oil is rubbed into an acrylic ground to deter sinking-in, how does this affect the “fat over lean rule”? If a canvas is prepared this way, can one still paint with a medium that has solvent in it?

    If a layer of paint is oiled out with straight oil, does this mean one shouldn’t use any solvent in their next painted layer?

    I prefer to use straight walnut oil for oiling-out because it is thin and adding solvent can lift the paint, but I have read on this forum that more bodied oils thinned with solvent are better for oiling out. Why is a bodied oil thinned with solvent superior to a thinner straight oil?

    Can a black area of a painting be oiled out as a final layer? Is the inability for a conservator to remove this layer later on the only issue, since I assume true black won’t develop a yellow cast?

    How long does the yellowing process take to appear if a painting has been oiled out as a final layer?

    If cold wax is used in a medium to create a more even color field (i.e. less variation in shine), can the painting still be oiled out?

    Thank you so much.

  • Question asked 2017-08-31 01:46:50 ... Most recent comment 2017-09-01 17:51:00
    Oil Paint
    Question

    ​Hello,

    I am in the process of gluing earth magnets (and /or metal strips) to the backside (at the top) of both paper and canvas based paintings as a way to hang the works from metal screws. Is there an adhesive that you can recommend that could be both secure, and removable without damaging the support? 

    In the future I'd like the option to remove the magnets/ metal strips for more traditional framing options, and am looking for an adhesive that has these properties.

    (The paintings are oil on canvas, and oil on arches oil ready paper.)

    Thanks!

  • Question asked 2017-08-29 16:07:20 ... Most recent comment 2017-08-30 16:44:26
    Egg Tempera Oil Paint
    Question

    ​Have a great question that came in response to an article on Dark Yellowing we put out:

    "I realize that this is outside the scope of your study, but I am curious to know if the egg tempera medium undergoes yellowing when it is placed in a dark invironment."

    Any knowledge of dark yellowing being an issue in egg tempera? Curious minds want to know.

    Sarah Sands
    Senior Technical Specialist
    Golden Artist Colors

  • Question asked 2017-08-25 23:45:53 ... Most recent comment 2017-08-26 16:03:34
    Art Conservation Topics Oil Paint
    Question

    ​I am wondering if there is a way to protect copper resinate from changing colors and turning brown, would an UV varnish help?

  • Question asked 2017-08-15 16:50:47 ... Most recent comment 2017-08-25 14:34:21
    Egg Tempera
    Question

    ​Hello MITRA,

    This question is a bit complicated, so please bear with me.  I have a fellow tempera painter who's experiencing cracking in the uppermost layers of her paintings. It starts out as very faint, fine lines that gradually increase with successive paint layers; the lines grow and evolve into fine "craquelure", and eventually tiny bits of paint flake off (within a few weeks of application).  

    Over the years I've heard from a handful of other tempera painters who've seen similar cracking, often (tho' not always) reported in areas of tianium white.  In general cracking (or craquelure) in tempera is rare, but with this most recent instance I'm recogninzing it as a problem for some painters and trying to understand it better.  I've come up with 5 reasons why cracking may appear in tempera paint:

     1. Excess binder. Too much yolk can create stresses as the protein molecules shrink with water evaporation.  

    2. Too thick a layer of paint. Tempera initially dries through relatively rapid evaporation of its water content, so if too dense a layer is applied it can crack as it shrinks (akin to a dried-out lake bed). 

    3. Adding too much water to tempered paint.  Once the paint is properly "tempered" it's possible to thin it significantly with water. However with TOO much water at some point the various components of the paint become so attenuated that it can create a weak paint film.   

    4. Over saturating underlying paint layers with water.  Research I've read on the effects of various solvents (both spirit and water) on egg tempera indicates that they can induce swelling in the paint films. If a curing paint film is compelled to repeatedly expand and shrink, this stress can weaken the bonds being formed in the polymerization process and create cracks (at least this is how I understand it; I'm not sure about this one...  By the way, none of the other reasons I suggest for cracking apply to the painter with the current craquelure problem; however she really saturates her surface with watery tempera paint, so much that the ground stays cool when her paint layeras are dry to the touch, suggesting there is residual mositure within - this is why I suspect this reason for her cracking problem, but I'm not sure). 

    5. Stresses in the ground and/or support. Cracks in the gesso and/or movement in the panel can telegraph up through paint layers.  

    My questions to the forum are:

    1. Has anyone else seen cracking in egg tempera paint layers? 

    2. What do you think of the above reasons?  Do they make sense?  

    3. Are their other potential causes of cracking?

    Thanks, Koo Schadler

  • Question asked 2017-08-19 11:48:53 ... Most recent comment 2017-08-22 21:59:14
    Ink Oil Paint
    Question

    ​I've read somewhere that shellac-based India Ink can be used for underdrawing before proceeding with an oil painting. Is that durable? Would the ink have to be full-strength, not diluted? I'm looking for an alternative to a solvent-thinned underdrawing that would still show through an Imprimatura. Would an ink underdrawing have to be completely covered by oil paint to be durable? I've seen Golden's article (Just Paint, Oct. 1, 2015) on underpainting alternatives (acrylics, watercolors, safflower oil-thinned paint and egg-oil-water thinned paint) and always wondered if those solvent-free alternatives needed to be completely covered with oil paint in order to be durable? For example, would a perimeter line in a solvent-free underdrawing need to be restated with full-bodied oil paint in order to be durable? Thank you for any thoughts.

  • Question asked 2017-08-19 16:30:15 ... Most recent comment 2017-08-20 01:54:54
    Oil Paint Art Conservation Topics
    Question

    ​Greetings,

    Perhaps this is out of the scope of the conservator, but I was looking at some very high res scans of a Caravaggio and looking for some professional insight into his working methods. Here is the scan: http://www.haltadefinizione.com/en/gallery/caravaggio-bacchus

    I know that reverse engineering a painting is difficult, but perhaps you have come across some convincing interpretations of how caaravaggio built his paintings- questions of source and optical devices aside, and I've read about the ambiguity of the incised lines- but can we speculate or measure his choice of grounds, layering process, glazing, mediums, working dark to light, etc? And this is obviously subject to change across works, but in this Bacchus, can you tell how he laid down paint to get to this end?

    His modelling of flesh tone seems 'ponced' or stippled on with a glaze, it is so delicate and doesn't seem to have any of the brush marks the lights have. 

    I've been reading V. Elliot´s Traditional Oil Painting, and he does some scholarly recreations of paintings, such as Bouguereau. Is there anyone that has does a similar analysis and receation of Caravaggio, that is accepted (I've seen some bad ones, and the work doesn't seem based on a grisaille to me)?


    Thank YOU!

  • Question asked 2017-08-17 22:02:15 ... Most recent comment 2017-08-18 23:23:30
    Grounds / Priming Other
    Question

    ​This may win the prize for the weirdest question... I have five maple panels that I sized and then later gessoed and left out on my porch to air dry. It's possible that a cat (or squirrel?) may have sprinkled them with their "marking fluid" while they were drying. (I've heard that cats are attracted to the smell of amonia.) There are a dozen or more shiny specs on each of the boards, which were laid end-to-end. And the peculiar and unpleasant odor is only slightly diminishing after a week and a half. I had thought maybe there was a reaction between the sizing and the gesso, but I think that would have resolved by now. So...if the panels have been sprayed, do you think it's a reasonable approach to clean them with vinegar and water 1:2? That's one of the home remedies that is suggested for spray on interior walls. I can wipe the specs off with straight water, but the odor seems to remain. I'm concerned about adhesion problems when I proceed with oil paint, or de-laminating further down the line. Alternatively, I could put another coat of gesso (water-based) on the boards, or an imprimatura of oil paint...? Any suggestions would be greatly appreciated!  :-(

  • Question asked 2017-07-13 10:14:14 ... Most recent comment 2017-08-18 12:41:36
    Watercolor
    Question

    A student recently showed me some watercolors of his that have a problem, hoping I could decipher it, but I don't know what's going on. Throughout several paintings there are areas where the paint is  (in his words) "disappearing" - initially the paint went on fine, but over time there are patches of paint loss that look a bit like a bug has been nibbling; or, another way to describe it, looks like someone pressed a paper towel with a squirrely pattern to areas of the paint while it was wet, lifting the paint (although, as mentioned, this problem didn't occur until after the paint had dried). Neither of these are the best description of the problem…I have photos, if there is a way to share images.  The paint loss is not limited to a single color and has occurred on several paintings with different types of supports.  All I could think of was minerals or salts in the water, precipitating out?  Any other ideas?

     

    Thanks,

     

    Koo Schadler

  • Question asked 2017-08-16 23:05:01 ... Most recent comment 2017-08-17 17:46:37
    Sizes and Adhesives Grounds / Priming Oil Paint
    Question

    ​Wondering about a couple different sizing options
    1. Gac 400 then two coats of Gac 100 then Rublev lead oil ground
    2. 2 layers of Gac 100 then Rublev oil ground

    How much of a difference will there be? Will the only difference really be in the canvas stiffness (with 1. being a stiffer canvas and 2. being more flexible)?

    Will there be any difference in how the oil paint sits on the surface?
    (For example) I do not like slick surfaces to paint on. I would like a semi absorbant surface. If I go with option 1, will the surface be too slick? Or will the overall surface be pretty much the same between the two?

    Thank you so much for any help!!



  • Question asked 2017-08-11 18:33:34 ... Most recent comment 2017-08-13 14:09:17
    Grounds / Priming Health and Safety
    Question

    Hello MITRA folks,

    Do you know if there are any alternatives to rabbit skin-based, solvent-based and acrylic-based grounds for both canvas and panels? I have read that methylcellulose can be subsituted, and a reference to shellac, but have read nothing definitive and scientific. This would be for oil painting, and I am looking for a low VOC, solvent-free, easy-to-use solution that would also be archival (or a support for oil painting that needs no ground (and no solvents to clean it) at all. 

    Thanks so much for any thoughts!

    Susan

  • Question asked 2017-08-09 14:26:38 ... Most recent comment 2017-08-11 19:14:16
    Oil Paint
    Question

    I was wondering if you have any advice/ways of testing adhesion between oil painting layers?  I have done a diy cross cut test with a razor blade and masking tape, but if I go by that thicker passages and impasto pretty much always fail, so it seems like overkill. On the other hand, a fingernail seems kind of weak, because I've not been able to scratch layers that I otherwise can peel or sand off relatively easily. 

    Thanks

  • Question asked 2017-08-08 17:06:40 ... Most recent comment 2017-08-09 15:19:08
    Health and Safety
    Question

    I will be mulling pigment and making paint for the first time and I want to be safe, what mask do you recommend me to buy (pigments might include vermilion, lead tin yellow, and azurite)

  • Question asked 2017-08-06 08:08:18 ... Most recent comment 2017-08-06 12:04:35
    Paint Additives Oil Paint Paint Mediums
    Question

    ​I have over some years been able to extend the life of oil paint on the palette and in small storage containers by the use of (Mark Carder's) Slow Dry Medium, in combination with the exclusion of air (oxygen). Mixed stock color is useable for two years and premixed values for two months in airtight glass jars.

    If I were to place a wet oil painting in an oxygen rich tent (storage bag) would I be able to accelerate drying to the point I could varnish earlier than the recommended six months?

    I were to place a wet painting and/or a wet palette in a carbon dioxide or argon rich tent would I be able to postpone the formation of a drying skin, thereby extending the open time of the paint and canvas?

    Thanks Denis


  • Question asked 2017-08-03 21:34:36 ... Most recent comment 2017-08-04 12:13:01
    Oil Paint Sizes and Adhesives
    Question

    ​How archival is oil painting on birch panels that are sized with a few coats of shellac? The panels are only 1/8inch thin and prone to warping as they are not cradled. Would shellac be alright to oil paint directly on top of if they were 1/4inch and cradled? If shellac isn't archival can you recommend a way to prepare panels that gives a similar feel when applying paint?

  • Question asked 2017-08-02 22:36:10 ... Most recent comment 2017-08-03 20:53:52
    Industrial and Non-Traditional Products
    Question

    ​I want to paint directly on Aluminum with Acrylic paint and also collage on the aluminum using Acrylic Matt Medium as the adhesive. I was told I should use a degreaser on the aluminum and than could directly paint on it. Would a solution of distilled vinegar, baking soda and water work as the degreaser. Do you have any other recommendations. I want the aluminum in places to show throught so I don't want to prime the aluminum.

  • Question asked 2017-08-02 19:22:20 ... Most recent comment 2017-08-03 20:46:07
    Oil Paint Solvents and Thinners Paint Mediums Drying Oils
    Question

    I am an oil painter and replaced Gamsol with oil of spike lavender about a year ago in an effort to make my studio less toxic. I've been mixing about one part spike lavender to two parts walnut oil for my medium, and adding a bit more walnut oil to the mix for subsequent layers. (I clean up with saflower oil and Murphy's oil soap). This medium has been working fairly working well but I've had a hard time finding concrete information on the stability of spike lavender in paintings over time. I found a post on this forum that explained "Painting with large amounts of any essential oil can lead to the formation of a weakened paint film." I was wondering if anyone could please elaborate on this? For instance, what would a safe amount of spike lavender be? Further, I know that walnut oil forms a less ideal film than linseed oil, but I prefer it for its less-yellowing nature over time. Are there conservation concerns about using walnut oil and spike lavender in conjunction?

  • Question asked 2017-08-03 10:55:12 ... Most recent comment 2017-08-03 12:29:42
    Oil Paint Scientific Analysis Varnishes Paint Additives Paint Mediums Art Conservation Topics
    Question

    ​I know that some varnishes such as Gamblin's GamVar and Golden MSA varnish have UV protection due to ultraviolet light stabilizer and filters. I presume that these are close to being transparent as it's used in a very thin layer of varnish.

    Do you know of any process or product where similar light stabilizers and filters can be added to the oil paint itself via additions to a medium? Would this compromise the paint film? I was wondering if it would work to increase the lightfastness of the pigments and potentially could be present in greater concentrations than in varnish?

  • Question asked 2017-07-29 02:22:43 ... Most recent comment 2017-07-30 13:22:28
    Varnishes Industrial and Non-Traditional Products
    Question

    ​I am interested in exploring the full range of sheen that can be obtained in art, from the mattest to the glossiest. I am painting on Dibond panels (currently with acrylics, but occasionally with oils). I am not particularly impressed by the usual gloss look of fine art varnishes. More and more I'm interested in this type of finish:

    https://www.youtube.com/watch?v=K0pXjV4zGDM

    But it seems that the best results are achieved by polishing with buffing compounds on top of 'super coating' varnishes (usually alkyd based?). The manufacturers claim that these super coatings are non-yellowing and flexible, chemically resistant etc. Here is an article:
    http://www.woodworkingnetwork.com/articles/tips_for_using_super_coatings_127702208.html

    I am aware that these varnishes will eventually scratch (or age) during the lifetime of a painting.
    How can I achieve the highest possible gloss while still keeping up with the good practices of painting?
    Are there any removable fine art varnishes that can be buffed up to this level of finish?

    Cheers

  • Question asked 2017-07-28 09:38:44 ... Most recent comment 2017-07-28 12:31:03
    Drawing Materials Grounds / Priming
    Question

    ​Hi,

    A friend who is an experienced metalpoint artist recommends Golden's Pastel Ground for metalpoint; he says it has more tooth, he's able to get richer darks, and thus prefers it to Golden's Silverpoint Ground.  I got some of the Pastel Ground to try and discovered it's transparent, not opaque - and I need opacity to cover the MDF support I'm applying the ground too.  Any considerations to combining equal parts Golden's Pastel Ground with either Golden's Sandable Hard Gesso, or Golden's Absorbent Gesso (both of which work well for silverpoint and I already have in the studio)? 

    I don't have Golden's Silverpoint Ground on hand, but may order to experiment with if it's sandable - can you get a readily sandable, perfectly smooth surface with that ground?

    Thanks,

    Koo Schadler

     

  • Question asked 2017-07-25 16:30:58 ... Most recent comment 2017-07-27 22:48:04
    Oil Paint
    Question

    ​Hello,

    I am working on some portraits where the accuracy of value is critical and for areas that have sunken in from previous sessions I have been oiling out by rubbing thin layers of linseed oil (I've tried raw, stand, refined, 50/50 linseed and Gamsol OMS) on the surface. I have read mixed reviews of putting an isolated layer of oil into the paint film structure, for fear of disrupting fat over lean, cracking, darkening, etc. It seems retouch varnish has similar concerns.

    Is this oiling out (or painting into a couch) a problematic practice, and if so, how can the color be restored in a more structural way while working? 

    Are there best practices to oiling out? Oil, technique ,etc.

    Grazie Mille

  • Question asked 2017-07-20 15:38:21 ... Most recent comment 2017-07-23 16:04:58
    Oil Paint
    Question

    ​Greetings,

    I came back to the studio today and some piles mixed tube colors of oil paint from yesterday have now 'skinned over,' though the paint below stil seems fresh and usable.

    Is it problematic to use this paint, removing the dried skin, and painting with as usual? 

    Does the paint below have the same properties as paint left on the palette without the skinning, or has the complexity of the oxidation of the oil now made this paint different somehow and less desirable, perhpas more lean...?

    Gracias


  • Question asked 2017-07-19 16:31:15 ... Most recent comment 2017-07-20 19:15:29
    Watercolor Ink Gouache Flexible Supports
    Question
    I would like to protect ink and watercolor paintings on thin rice paper (unsized Xuan paper) by mounting them. They are quite big - around 100x70 cm each. I'm not sure how to proceed with this - should I dry or wet mount? Is it better to use thicker paper (bristol) as backing, or maybe a fabric like polyester? Would methylcellulose glue be sufficient?
  • Question asked 2017-07-19 19:16:11 ... Most recent comment 2017-07-19 20:24:46
    Grounds / Priming Oil Paint Flexible Supports
    Question

    ​Hi. I have a roll of oil primed linen from a company that describe their production process like this -  "For an ‘oil canvas’, zinc white is used as the primer, bound with linseed oil."

    Given the issues associated with the use of Zinc what are your recommendations - use this product or not?

    Many thanks.

  • Question asked 2017-07-15 13:53:10 ... Most recent comment 2017-07-19 11:45:11
    Egg Tempera Grounds / Priming Oil Paint Technical Art History
    Question

    Oil paints become increasingly transparent with age, due to changes in the refractive index of the binder, I believe.  For this reason, I've seen white grounds recommended as generally preferable to dark toned grounds (so as the paint grows more transparent, the light values in a painting aren't darkened by an underlying dark ground).  A few questions relative to this:

    1.  I believe the same is true for egg tempera paints - they become more transparent with age, yes?  

    2. Is it true of other paints?

    3. Is there concern or evidence to show that the converse is true;  that paintings on white grounds, as they age, lose some of the depth in their dark values (because the white ground shows through the increasingly transparent paint), to the detriment of the painting's value pattern?

    Thanks,

    Koo Schadler

  • Question asked 2017-07-14 13:05:41 ... Most recent comment 2017-07-14 19:13:05
    Flexible Supports Industrial and Non-Traditional Products Scientific Analysis
    Question

    ​Hello,

    Does anyone know of or have access to tests of flexible supports that include synthetic canvases? I clearly remember mention of an ongoing test comparing flexible supports on the no longer available AMIEN forums. The thread was a discussion on synthetic canvas and indicated that at least some synthetics greatly out-performed traditional canvas.

    I was so impressed that I eventually asked a textile designer for help producing a heavier-weight synthetic canvas that is wider and more affordable than I could find on my own. I've been working with this canvas for a few years, and recently interviewed the designer (Scott Bodenner) about the project. Talking to someone with a textile industry point of view was fascinating. There are differences in how testing is done for commercial textiles and also a concern for recycling and sustainability that I don't encounter much in reading about artist materials. The interview is posted on my own website at: 

    http://sloweye.net/scott-bodenner-recycled-synthetic-canvas/

    But I'd still really like to know how the test I saw mentioned on AMIEN turned out! Fingers crossed someone remembers what that was...

  • Question asked 2017-07-12 16:12:41 ... Most recent comment 2017-07-14 16:35:36
    Oil Paint
    Question

    What is the opinion on the usage of non-traditional drying oils? I have read about the usage of candlenut, perilla or tung oil in some art works, but there's not much I could find in terms of conservation issues regarding these.

  • Question asked 2017-07-11 17:21:59 ... Most recent comment 2017-07-14 12:36:41
    Oil Paint Solvents and Thinners Paint Additives
    Question

    ​Hola Mitra,

    I have been looking for more information about the safe or recommended amount acceptable to thin oil paint with solvent. I'm using tube paint and odorless mineral spirits. In the past I have sketched in a drawing on top of the ground of acrylic gesso on canvas with a brown earth and liberally diluted the paint near watercolor consistency so that it really flows. (I then add straight tube paint or progressively less oms with the paint, and sometimes fatter glazes on that.) But recently I've read oil paint shouldn't be thinned beyond a whole cream milk consistency to avoid problems such as future delamination and breaking down the oil paint film (and polymers?). Personally I haven't seen problems in my paint films, not yet anyway, though sometimes it seems some tinted solvent has seeped through and is visible on the reverse side of the painting- like some stained spots...

    More information surrounding this topic would be appreciated.

    Specifically, are there established guidelines for how much oil paint can be thinned with oms?  Is oms even a good diluent for oil paint, or are other solvents preferred (Essential Oils, Turps, mediums with stand oil, alkyds) especially in this lower layers? If this thinned layer leaves the ground with much tooth available for thicker paint to adhere to, would delamination problems persist. And I've come across the idea that oms evaporates fully and thus doesn't alter the lean-ness of the paint once it's gone, is this true?

    Thank you for any time you can space on this topic!


  • Question asked 2017-07-03 13:45:56 ... Most recent comment 2017-07-08 18:20:28
    Oil Paint Paint Additives
    Question

    ​Greetings,

    I would like to apply oil paint on canvas (large scale) in thick smears similar to Richter, but am looking for some insight into the best practices for this approach to avoid problems such as wrinkling, cracking, excessive drying times, etc. 

    Do we know if he is altering his paint from tube consistency? Would this be recommended and if so what additives/ amendments? 

    (Implict question: I know you recommend rigid supports for thick paint, but is there a practical solution for large paintings, say 4 x 6 feet?)

    Mille Grazie

  • Question asked 2017-07-03 12:49:24 ... Most recent comment 2017-07-08 18:11:40
    Sizes and Adhesives Rigid Supports Industrial and Non-Traditional Products
    Question

    "Artist quality" PVAs and other such sizing products are too expensive and hard to obtain for me. There is no BEVA/MSA Varnish/B-I-N either. What I can obtain are various acrylic primers made for porous surfaces, regular PVA glue (the manufacturer states that the pH is 6-7), as well as methylcellulose wallpaper glue and boiled linseed oil.

    The acrylic primers are basically watery liquids that smell just like acrylic mediums. Their manufacturers typically state that they are made from acrylic dispersions, and that they are made for priming porous surfaces, unifying them and decreasing their absorbency - some add that they still let water vapor pass through after drying.

    I was wondering which one of these would work the best for sizing before laying down a layer of (artist quality this time) acrylic ground. The acrylic primers seem to be the best option, but I read differing opinions about the properties of hardware store products. I know methylcellulose is a good size, but I don't know how well it would perform on surfaces like hardboards and fiberboards.

    As for the boiled linseed oil, I'm not sure whether it wouldn't reduce the adhesion of the acrylic ground.

    I'm open to suggestions if there's something else I could try.

  • Question asked 2017-07-06 03:10:50 ... Most recent comment 2017-07-06 18:28:16
    Oil Paint
    Question

    ​Greetings,

    I've recently read on another forum (NP) a great article that said oil paintings when possible should be made by using the most opaque colors in the lower layers and layered up toward more transparent pigments. However, it seems many paintings from the past used brown grounds or thinned brown (umber or sienna?) as a drawing color in the lower paint layer. (Another recommendation that was surprising to read was to paint from light to dark, and thus moving from light and opaque lower to dark and transparent upper layers.) 

    Which pigments do you recommend "blocking in" a drawing in the underpainting, and is the opaque to transparent layering order generally accepted?

    Is my read of many historical painting practice off, or do we just understand the chemistry better and have new best practices?

    Thank You for this amazing resource!

  • Question asked 2017-06-29 05:56:17 ... Most recent comment 2017-06-30 08:26:07
    Health and Safety
    Question

    Looking through Safety Data Sheets for various art supplies, I have noticed a strange discrepancy between the information provided by various manufacturers. A good example is "naphtha (petroleum), hydrotreated heavy", with CAS number 64742-48-9. A basic search through toxicology databases shows that it is considered both mutagenic and possibly carcinogenic (1B), with numerous reported adverse health effects (https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/115111). Yet, looking at the SDS for Gamblin's Galkyd mediums (https://www.gamblincolors.com/wp-content/uploads/2016/05/SDS-Galkyd-Galkyd-Slow-Dry.pdf), there seems to be only information about them being flammable, a skin irritant, toxic to aquatic life and causing drowsiness. My question is then: which information should I go by? Am I risking cancer or chronic painter's syndrome by using these mediums? It seems like the exact same substance that, in other manufacturers' products, causes cancer is safe here. How is that possible?

  • Question asked 2017-06-29 10:42:26 ... Most recent comment 2017-06-30 07:13:07
    Egg Tempera Flexible Supports Grounds / Priming Scientific Analysis Technical Art History
    Question

    Yesterday I went to the Boston Museum of Fine Arts to see the show of Botticelli and his contemporaries.  It's a beautiful collection of work, and I marvel that the museum was able to get 500 year old paintings from Italy to Boston - a real treat. Given that the 15th c. was a transitional time for paint (egg tempera to oil) I was curious to see the labeling.  Most pieces were simply "tempera on panel"; several were "tempera on canvas"; a few were either "tempera and oil" or "oil". 

    I wish labeling in museums was more consistent and specific.  However I appreciate that museums are generally challenged by finances, resources, time.  My guess is that different museums have different approaches and philosophies to analyzing mediums (it's not necessarily every museum's priority); a lender has to accept what the lendee says about a piece; there is not enough money for conservators to definitively analyze ever work in a collection; it's still difficult to say for sure what a 500 year old painting is composed of (especially if mediums are mixed, i.e. tempera and oil).  My questions are...

    1. Any other thoughts on way medium labeling can be vague?  

    2.  Some works (as evidenced by the brushwork and finish) were clearly egg tempera.   Other works looked so rich and painterly it was hard to believe they were just tempera; hints of tempera brushstroke were evident, but other areas were smoothly and thickly painted. Is it possible there’s some oil paint in the mix and the works  aren't accurately labeled?  Or would the varnish that was apparent on most of the paintings be sufficient to give these egg temperas an oil look?  Or maybe it's that the Renaissance masters were capable of a much greater range of effects in tempera than they’re generally credited with (i.e. they did more than just hatchstroke, as is often claimed)?  I’m trying to better understand what’s going on in these “quintessentially egg tempera" masterpieces (that, in fact, often don’t look like “quintessential” egg tempera). 

    3.  A traditional chalk and glue ground lacks flexibility, and egg tempera paint become brittle with age – so I don’t understood how a 500 year-old egg tempera survives on canvas (i.e. Botticelli’s Birth of Venus).  Could there be some oil emulsified into the ground or paint?  I know the Birth of Venus is painted thinly (you can practically see the weave of the canvas in parts, it seems to me) – would the thinness of the paint layers be sufficient to deal with the flexibility in canvas?  Or are most temperas on canvas backed by a solid panel (tho’ I don’t think the Birth of Venus is….).  In short, how to explain egg tempera on canvas?

    4.  As mentioned, much (most?) of the work appeared varnished.  Is there a way to determine which of the varnishes are original, which added in later centuries?  How do conservators address a Renaissance painting that enters their collection and has a varnish?

    Thanks for your help in better understanding this wonderful but complex period in art history.  

    Koo Schadler

  • Question asked 2017-06-28 20:07:54 ... Most recent comment 2017-06-28 21:48:42
    Oil Paint Varnishes
    Question

    ​Hi everyone,

    I have a problem and hope to get some advice from the collective wisdom here. I finished a painting about 2 months ago, and let it sit for a few weeks before spraying it with retouch varnish so that I could refresh the colours and get a decent photo. I then moved the painting into a spare room that is seldom used, and left it there to cure. Today I discovered that my husband went into the room a few days ago and moved the painting . . . he leaned it *face down* against a sofa. When I moved it today, it actually made a faint sound as I pulled it away from the sofa, something like pulling low-tack tape off a wall. :( It looks now like there is a spot where the paint looks a bit flat, and otherwise there is lint/dust that I cannot brush off with my fingers. Do I need to use mineral spirits and strip off the retouch? Or is there something else that I can use to clean the surface without disturbing the retouch? Thoughts? Advice?

    BTW, in case it helps: I painted this one in layers, using a thin layer oleogel as a couch between layers. The retouch varnish is Winsor & Newton, because I've found that other brands (particularly Krylon) don't get along well with the oleogel.

    Thanks in advance.

     

    Jennifer

  • Question asked 2017-06-26 03:39:20 ... Most recent comment 2017-06-28 18:42:30
    Oil Paint Pigments Scientific Analysis
    Question

    ​Hello,

    I'm interested in using PBr33 due to it's very dark opaque nature.. It's used by Sennelier and Schmincke in a few of their oil paints. However as it's made using Zinc I'm just concerned it could make the resulting paint film brittle in the same way zinc white can.

    But I don't know if the combination with the iron and chromite would avoid this issue.

    Does anyone have any opinions on this?

  • Question asked 2017-06-05 05:50:42 ... Most recent comment 2017-06-28 17:32:02
    Rigid Supports Oil Paint Acrylic Sizes and Adhesives
    Question

    I have recently read that the outgassing of formaldehyde from urea-formaldehyde used to manufacture HDF and MDF is a problem when it comes to conservation, since it can influence the acidity of both the work and the environment, leading ​to possible degradation of the artwork. I also read (Getty's "Facing Challenges of Panel Paintings Conservation", part 3 by Paul van Duin) that urea-formaldehyde itself degrades over time and the author estimates its longevity (when protected from light) to be a couple of decades. In light of this, I was wondering if hardboard (wet process board) wouldn't be a better choice, since it doesn't contain UF?

    On the other hand, I used to coat the panels I paint on with a water solution of PVA with a pH of 6-7 (according to manufacturer), and I read that PVA can be a source of acetic acid, but I'm not sure if this is relevant.

  • Question asked 2017-06-28 10:17:57 ... Most recent comment 2017-06-28 15:18:39
    Flexible Supports
    Question

    ​how best to repair torn painting on canvas

  • Question asked 2017-06-25 01:04:07 ... Most recent comment 2017-06-26 18:58:10
    Sizes and Adhesives Rigid Supports
    Question

    ​I am wondering if it is okay to use a heat press to mount linen to a panel using Beva 371 film after the painting has been completed. I like to glue it afterwards because not every painting works out, and I'd like only glue the ones that I (or a buyer) determines a success. I heat it at 150 degrees for 6 minutes twice, once to attatch the glue film to the board, and a second time to adhere the linen to it.  I am painting with oil paints using Gamsol and linseed oil as a medium, and painting without a lot of texture (which I have found that the heat press flattens), and gluing them to boards of MDF or hardboard. I have not noticed any issues, but am concerned that somewhere down the line the fact that the painting has been heated up might pose a problem. Additionally, I am wondering if I need to seal or size the support before I adhere the linen to it.  Thanks so much. This is a great forum. 

  • Question asked 2017-06-25 21:15:17 ... Most recent comment 2017-06-25 21:53:43
    Rigid Supports
    Question

    ​It is recommended to size and/or prime a wood panel (eg. birch plywood) adequately to prevent oil penetration. What exacly would happen to the panel if a substantial amount of oil was absorbed into it due to inadequate or no panel preparation (bare wood).  Would the acid in the oil damage the wood?

  • Question asked 2017-06-18 13:00:16 ... Most recent comment 2017-06-19 10:30:50
    Gilding
    Question

    ​Best recommendations for an oil mordant for use to gild an icon?

  • Question asked 2017-06-09 16:12:21 ... Most recent comment 2017-06-15 20:32:09
    Sizes and Adhesives Paint Mediums Oil Paint Drying Oils
    Question

    I’m hoping someone can help me with two issues I’m having with painting:

    1. I am using oil sticks to paint on muslin fabric or even a polyester for my canvas, and I'm trying to see if there is a way to avoid the fabric from breaking down over time because of the oil based paint. Because of the type of painting I am doing, I wet the canvas first with a spray bottle and therefore I can’t seize the canvas prior to applying the paint to the canvas using traditional methods such as jesso. 
    2. Because I am applying the oil sticks to a damp fabric, the drying time is extended significantly.  

    Any advicde would be greatly appreciated. Than you.

  • Question asked 2017-06-02 14:48:33 ... Most recent comment 2017-06-15 16:36:18
    Paint Additives Oil Paint
    Question

    ​Greetings,

    I have been trying to modify oil paint for textural effect and my goal is to make the paint thick sticky and ropey/ stringy. Auerbach sometimes seems to have gotten a similar paint quality where the rheology of the paint is highly thixotropic alla Lead White. I've also been thinking of the quality of silicon caulk as the texture I am after. 

    I have expeirmented with adding stand oil, dammar, clay made into paste, alkyd, etc but these tend to 'shorten' the oil, lowering the viscocity (with the exception of the clay). My next step is to see what marble or glass powder does. I have a (Daniel Smith) tube of transparent blender made with alumina hydrate that is perhaps the closest I've found for the texture I am after.

    Any suggetions for this type if paint modification would be helpful. 


    Thank you!

  • Question asked 2017-06-14 13:40:09 ... Most recent comment 2017-06-14 23:20:40
    Oil Paint
    Question

    ​I used an aluminum panel for a painting support for an oil painting for the first time. A month after the painting dried to the touch, I wrapped it unvarnished  in acid-free tissue, wrapped in foam, then in bubble wrap in a cardboard box on a flight. It was wrapped this way for about 1 week. When I hung it for my exhibition I noticed strange splotches that resemble mold. They are not uniform and were not there before packing. The aluminum was purchased at an art store with plastic vacuum sealed to both sides. I took off the plastic and primed it with 4-6 layers of Grumbacher Gesso for oils, sanding between each layer. I used Rublev Raw French Umber thinned with Rublesol for the underpainting, followed by Rublev paint straight from the tube with no medium added. The main colors I used were Lamp Black and Lead white. Is there some reason you can imagine that would cause this type of reaction? Will it go away when I varnish? I've read that using denatured alcohol and lead primer would help prevent this in the future (whatever this is), but wouldn't so many layers of gesso be good enough? Thank you!

  • Question asked 2017-06-09 23:14:16 ... Most recent comment 2017-06-10 09:16:00
    Varnishes Technical Art History
    Question

    ​Hello. I'm not sure if this question really belongs with the Varnish questions, but I couldn't find any better matches. I was reading an abstract from the journal Nature in which some Tate Modern conservators described their research into Rothko murals.* In their words, "Rothko [...] applied phenol formaldehyde to prevent layers from blending into one another." I imagine this working something like workable fixative between paint layers. Is that correct? Are there other documented uses of phenol formaldehyde for this purpose? How would the use of it affect paint adhesion in layers above? 

    I'm not aware of too many companies selling anything like this, although Lefranc & Bourgeois offers "Harlem Duroziez drying medium"** which they say contains phenol formaldehyd resin. Are there other manufacturers which offer it in a liquid or spray form?

    * https://www.nature.com/nature/journal/v456/n7221/full/456447a.html

    ** http://www.lefranc-bourgeois.com/beaux-arts/telechargement/A_TELPDF_2010092817171362.PDF

  • Question asked 2017-06-07 13:25:41 ... Most recent comment 2017-06-09 12:31:01
    Industrial and Non-Traditional Products
    Question

    ​I am looking for an adhesive to adhere tar paper to a masonite panel. Any suggestions? Thank You!

  • Question asked 2017-06-07 18:20:51 ... Most recent comment 2017-06-08 23:23:36
    Rigid Supports Sizes and Adhesives
    Question

    I want to attach unprimed linen to Gessobord and then prime with lead oil ground. I want to use cradled and sealed Gessobord to skip steps of sealing/cradling even though a bit more expensive. My question is which adhesive is better – Lineco Neutral PH Adhesive or Beva Adhesive? Note: I don't want to deal with the Beva in a film form. it sounds too tricky. Thank you for this site! 

  • Question asked 2017-06-07 10:57:25 ... Most recent comment 2017-06-07 11:25:28
    Health and Safety Oil Paint Paint Mediums
    Question

    I sometimes use Black Oil ( linseed oil boiled with lead) to speed up the drying time of the oil paints. Once the paint is dry if you sand or scrape the surface does the presence of Black Oil in the paint present a health issue with the airborne particles ?

    Many thanks

    Jim G

  • Question asked 2017-05-31 11:56:54 ... Most recent comment 2017-06-01 22:19:28
    Acrylic Paint Additives Paint Mediums
    Question

    My acrylic paintings sometimes show a noticeable amount of color lifting (particularly when using a relatively large amount of retarder) - rubbing a wet cotton swab causes a small amount of color to be left on the cotton. There seem to be no major adhesion failures, even in cases where I might have used more than the recommended amount of retarder. I was wondering if I should secure such layers of paint by brushing a layer of medium on top? I remember reading that it's generally a good idea to provide such a protective layer in practically all cases.

    And in case this ever happens, what would be the best course of action if the paint remained "tacky" due to too much retarder?

  • Question asked 2017-05-26 18:39:48 ... Most recent comment 2017-05-26 19:27:30
    Grounds / Priming Acrylic Oil Paint
    Question

    ​I know that the sensitivity that acrylic polymer films have to solvents presents challenges when it comes to the cleaning of acrylic paintings. Is there a similar concern for oil paintings executed on an acrylic ground? Or do the layers of oil paint (assuming that the ground is well covered) provide an adequate barrier against the action of sovents used in cleaning?

    -Ben

  • Question asked 2017-05-14 17:05:44 ... Most recent comment 2017-05-21 02:21:32
    Rigid Supports Oil Paint Flexible Supports
    Question

    ​I know that historically, linen with a close, tight weave was prefered for its strength. If one is mounting (pre-primed) linen to a rigid panel rather than stretching it, is there any particular reason to worry about using a loose-weave linen similar to what would have been called an "Étude" canvas in the 19th century? "Loose" meaning that there is enough space between the yarns that you can see tiny squares of the ground from the back of the linen. 

    ArtFix L21C and Fredrix Paris #908 HP are modern examples of this type of linen. I like the texture a lot on both, but am not sure if the loose weave is likely to be an issue in mounted linen. 

  • Question asked 2017-05-02 07:32:24 ... Most recent comment 2017-05-17 23:25:55
    Sizes and Adhesives Studio Tools and Tips Oil Paint Flexible Supports
    Question

    ​I like to use Beva 371 film to mount oil-primed linen to tempered hardboard. It usually works great, but sometimes I'll have a spot or two right on the edge of the panel where the linen just doesn't want to adhere, and remains loose. Going back over these spots with my tacking iron never seems to help. 

    I always adhere the Beva film to the panel first, and then mount the linen. Would it be better to start by attaching the film to the linen? Or, could I take out some "insurance" by attaching a layer of film to *both* the linen and the panel? 





  • Question asked 2017-05-09 09:23:46 ... Most recent comment 2017-05-15 11:04:12
    Oil Paint
    Question

    ​There has been some discussion on another forum regarding colour matching for touch-ups to sections of oil paintings. The problems seem to be related to adding mediums - especially mediums containing solvents (such as alkyd mediums).  Colours sometimes dry lighter or darker than expected - depending on the medium used and whether medium was added before or after colour matching. I was wondering if there are any pointers from how conservators handle matching colours for inpainting that would help artists in matching colours for tehri own touch-ups.  Do you use just straight paint? Add medium before or after mixing the right colour?  What medium do typically you use? Any insights into your typical in-painting process would be helpful.

  • Question asked 2017-05-08 10:26:21 ... Most recent comment 2017-05-08 11:11:24
    Oil Paint Drying Oils
    Question

    ​Is it OK to put an oil painting out in the sun to dry to speed up drying?

  • Question asked 2017-05-02 13:49:43 ... Most recent comment 2017-05-02 21:04:28
    Question

    ​Hi.  I'm an oil painter considering using KILZ 2, (latex water-based primer, sealer and stain blocker composed of  Titanium dioxide, Nepheline Syenite, Limestone) as a sealer for maple panels.  I will use 4 or more coats of acrylic gesso (either Golden or Art Board) after the KILZ.  I hear that KILZ is a good seal for panels but also know that industrial grade materials aren't always tested/recommended if the intention is to build an archival surface.  Do you recommend KILZ or should I stick with GAC 100?  Thank you. 

  • Question asked 2017-04-21 23:45:13 ... Most recent comment 2017-05-02 07:24:45
    Rigid Supports
    Question

    ​Dear Moderators


    Thank you for this wonderful website. So glad to see AMIEN has a successor.

    I plan to paint on some RSG sized canvas and then (if the painting works out) to glue it to a rigid support. I had hoped to use my untempered Masonite as substrate to glue the textile to but recently read here that tempered is far better (however I don't hold out much hope of getting that product here in Australia). I am very much aware of all the disadvantages of using RSG (have been reading about them for decades) but I strongly prefer the working qualities it imparts to the surface I paint on. Also I understand that RSG is much less problematic when used on a rigid support, if all precautions are taken (such as sizing and priming both sides and also varnishing both sides at the proper time etc). I had planned to just go ahead and glue the linen to the Masonite and then do the painting (much more straightforward) rather than size a stretched canvas, paint on it and then glue it on to the Masonite. However I can't do this till I find a source of tempered Masonite. In the meantime I want to paint. My question is: is it unwise to use hot RSG to glue a finished painting to a substrate? Is it likely that the hot glue would damage the painting? 

  • Question asked 2017-04-29 02:59:41 ... Most recent comment 2017-05-02 07:21:30
    Art Conservation Topics Oil Paint Scientific Analysis Technical Art History
    Question

    ​Will all oil paintings eventually crack, even if painted on a rigid surface with a good oil binder in the correct ratio and avoiding pigments like Zinc?

    Do these good practices only extend the time it takes before cracking occurs?

  • Question asked 2017-04-20 12:46:55 ... Most recent comment 2017-05-01 14:21:42
    Acrylic Grounds / Priming Rigid Supports Flexible Supports Art Conservation Topics
    Question

    ​Debating whether to use pigmented Shellac BIN or GAC 100 as sealer.  From what I've been told, Shellac BIN is a sealer, GAC 100 is not.  (regular Shellac can dissolve acrylic paint due to alkaline sensitivity to ammonia but Shellac BIN seems to be ok)

    GAC 100 reduces SID, but so can Shellac BIN.  

    It seems like Shellac BIN is winning out here... I plan to put a couple layers of Gesso on top of either Shellac BIN or GAC 100 before painting of course.  If Shellac can do what GAC 100 can do but it is a true sealer wouldn't Shellac BIN be a better choice?  

    Regarding WARPING: Someone told me that shellac also can prevent warping due to blocking moisture.. is this true?

    I'd like to eventually work bigger than 48" at some point and use the thinnest plywood possible (prob birch) to keep it light and of course cradle and brace it with supports.  But what are your thoughts as to warping at this size?  Would getting 1/4" be too thin?  What if I put 3 layers of Shellac BIN?

  • Question asked 2017-04-30 16:40:25 ... Most recent comment 2017-05-01 09:16:29
    Varnishes
    Question

    ​On Dec 2015 I finished a painting which later I varnished with Gumbacher Matte Dammar in Spray (4 months later).

    Last October the owner asked me to give it another coat of varnished (which I didn't know is not recommended).  Then I gave a coat with a cheap liquid matte varnish becayse I didn't find a good brand).  While I was applying it, the painting started to dilute a little bit.  I don't know if that was due the thin sprayed former coat or another reason. I could handle to eliminate marks and had a very good finish. However spots as if sinking in are appearing now.

    I have to fix it, but I don't know how.  I've never removed varnish before, so I'm afraid of doing so. Some solutions come to my mind.

    1. Varnish again (I know it's not good to use gloss over matte so I thin ther painting could  maybe stand another matte coat)

    2. Buff with cold wax to get an even surface.

  • Question asked 2017-04-28 07:57:35 ... Most recent comment 2017-04-28 22:18:57
    Varnishes Oil Paint
    Question

    ​Does anyone know if MS2A resin is still being produced? I've been looking for a source online, but haven't had any luck finding one.

  • Question asked 2017-04-27 07:01:42 ... Most recent comment 2017-04-28 21:17:05
    Rigid Supports
    Question

    ​Dear moderator


    Could you please advise how one might go about removing a painting done on linen from a panel (to which it has been adhered using acrylic medium) in the event that the panel has proven to be an unsuitable support or become damaged in some way? Or simply because the painting done originally didn't work out and one wants to glue a new piece of linen to the panel? I have tried removing linen from panel under the latter circumstances (when the painting didn't work out and was destined for the rubbish bin) , simply by pulling it off but found it virtually impossible. What solvents might a conservator use to achieve detachment in the event of a painting that needs to be saved?

  • Question asked 2017-04-16 16:43:34 ... Most recent comment 2017-04-24 14:30:11
    Oil Paint Art Conservation Topics
    Question

    ​Hello, 

       Someone on another forum (who lives in a warm climate) recently mentioned deliberately placing paintings in the sun to speed drying. They do it  both when finished and between layers. They mentioned that paint dried to the touch in a matter of hours. It made me curious. It sound convenient but I suspect that there are some inherent dangers to this approach.  I looked through the resource documents and there were hints that it was not a best pratcice but I couldn't find any explicit information. Any insights into potential problems with this practice?

       Thanks in advance.

  • Question asked 2017-04-20 20:05:55 ... Most recent comment 2017-04-24 11:01:00
    Acrylic Watercolor Gouache Egg Tempera
    Question

    ​From what I know, there is no limit to how much watercolors can be diluted when painted on paper. I was wondering if the same can be said of all the other water-soluble paints. Is it okay (in terms of durability of the finished work) to dilute:

    1. Acrylics
    2. Gouache
    3. Tempera (egg and non-egg)
    4. Inks

    as much as one wants if painting on an absorbent support, like paper? I read that the absorbency of the fibers ensures that the pigments are trapped within the piper, so there should be no conservation issue in that regard. Is that true?

    Also, should such works be varnished, and if so - with what?

  • Question asked 2017-04-09 12:32:20 ... Most recent comment 2017-04-11 20:18:00
    Acrylic Paint Additives Art Conservation Topics
    Question

    I know that acrylics can be made less durable by adding too much water or extender/retarder to them. I was wondering if this could be remedied later on by either

    a) coating the weakened layer with medium

    b) overpainting the weakened layer with acrylics that haven't been overextended or oils

    ?

    Would sealing the overextended layer with medium/paint have a similar protective effect as painting over tempera with oil?

  • Question asked 2017-04-09 11:54:22 ... Most recent comment 2017-04-11 18:23:00
    Rigid Supports
    Question

    ​I recently found online a kind of artist ACM panel with an anodized surface. The store that makes the panels claims the surface is porous enough to paint on directly with oils and acrylics, although I'd personally want to prime the panels first. Anodized aluminium as a painting support seems quite uncommon - however I did find at least one well-known artist, David Dunlop, who regularly uses it. And so I was wondering, are there any problems associated with priming then painting on anodized aluminium? As always, any advice would would be appreciated. Many thanks, J.

  • Question asked 2017-04-11 07:01:58 ... Most recent comment 2017-04-11 11:17:00
    Oil Paint
    Question

    Hello MITRA,

    On one of your resource handouts you say, "Some artists choose to place their paintings in direct sunlight for a certain period of time as UV light can break up some of the chemical bonds that are responsible for yellowing."  What length of time, more or less, is it suggested that an oil painting be exposed to sunlight to counteract yellowing?  Any caveats, besides being aware of fugitive pigments? 

    Thanks 

  • Question asked 2017-04-08 22:00:47 ... Most recent comment 2017-04-09 20:54:00
    Art Conservation Topics
    Question

    ​Hi there

    I've arrived here from the Wet Canvas forums, following a thread I was interested in, regarding damage to the acrylic "gesso" of a canvas, and subsequent oil strikethrough. Many respondents, in their answers, referred to the danger of "oil rotting the canvas", and indeed, searching this forum, found similar references. The problem I have is: I've never seen oil rotting a canvas. I've searched the internet of course, but may just be looking in the wrong places.

    I have some student canvases, they are about 25 years old, with paint stains on the side of the stretched canvas. There is no sign of degradation of the weave.

    oil-stains.jpg


    I have also read (I don't have a reference) that oil could be getting the blame from damage bry damp and mold in some cases. Is it possible that the fatty acids in Linseed Oil become effectively neutralized in the polymerization process, or simply locked up in the mass of fillers and pigment, and do little damage to the weave? I'm wondering what the evidence is to support the case for "oil rotting", and if there are photographs?


    Thanks!




  • Question asked 2017-04-09 18:53:54 ... Most recent comment 2017-04-09 19:36:00
    Flexible Supports Acrylic
    Question

    ​In the summer of 2016, I painted a 9-inch by 12-inch painting on 7/8-inch-deep Masterpiece "Vincent Sausalito" all-cotton stretched canvas. I added two coats of Golden acrylic gesso on top of the manufacturer's gesso, and then the painting was done in Golden acrylics. I framed it with a Nielsen aluminum canvas-depth sectional frame. It hung through the fall and winter in a winterized cottage in  northern Michigan, with the central heating system turned off.

    In early April of 2017 I found the painting in below freezing temps, in order to retrieve and varnish it. It apparently had undergone "planar" warping of the canvas surface, to use a term I've picked up on this forum. Over the course of a couple weeks in a separate year-round heated home, the warping has disappeared and the painting now looks fine. Ideally, I wanted to leave the painting year-round at the cottage, and am wondering if I should cut the painted canvas from the stretcher bars and glue it to 1/8-inch-thick Ampersand Hardbord with acrylic medium? First sizing the board on both faces and all four edges with acrylic medium. Was this sagging likely caused by the temperature change? Thanks for any insights and/or suggestions.

  • Question asked 2017-04-07 07:32:49 ... Most recent comment 2017-04-08 22:42:00
    Flexible Supports Grounds / Priming Art Conservation Topics
    Question

    ​Hi Mitra friends, 

    I originally posted this question on WetCanvas and they suggested I would ask it here to get a more in depth response. 

    I found many topics covering cracks in painting, but I promise this is not exactly related. 

    I spent many hours on a painting for which I stretched out the canvas myself, two layers of pva size and oil priming on top. 

    The painting itself has been built with many thin layers of oil paint with a little liquin to thin and accelerate drying of oils.

    Everything was going fine, but a few days back, the canvas fell from the easel and hit a chair corner. The fabric is absolutely fine, not even stretched out, but the area of the painting which hit the chair cracked a bit. 

    I was very upset and in hopes that the priming was intact, I tried to cover the crack with another layer of oil painting. 

    It seems to me that the sizing and priming were damaged due to the fall as the paint I applied afterwards went through and appeared on a cracking shape on the backside of the canvas. I'll try and post a picture with this for observation. 

    I was always told that oils will rot the canvas if it gets in contact with it (even though it might take years) but I wanted to know if there's any way I can avoid that from happening making the area "healthy" again? 

    Some people also said that the thin layers of oil will not damage the canvas if I apply acrylic primer on the back of the affected area? 

    I hope you'll be so kind to share any solid information you have on this issue?

    Thanks for reading! 

    CrackedPriming.JPG            

  • Question asked 2017-04-05 21:27:04 ... Most recent comment 2017-04-05 21:58:00
    Oil Paint Animal Glue Varnishes Flexible Supports
    Question

    ​I have had to withdraw a20170304_085913 - Copy.jpg painting for sale because of something that went wrong in its structure, sadly. This started on raw linen, rabbitskin glue (I don't use that anymore) I used oil priming- titanium with a heaping tablespoon of quality lead white paint and a small amount of quality turps. It dried several months and I used universal varnish on it. I don't heavy varnish, but a gallery in a different (dry) climate thought it needed more varnish. I bought the same brand etc and sent it to them and a respected artist with the same training added another coat. When I got the painting back, I loved it! It looked glassy and I preferred the look. However, this painting has always been the worst reactor to humidity changes of all my work. It's got crossbar supports, yes. It's now 13 years old and 2 years ago began to dimple.

  • Question asked 2017-04-05 04:29:19 ... Most recent comment 2017-04-05 15:56:00
    Flexible Supports Oil Paint
    Question

    ​Hello,  

    I have a few  questions about polyester canvas as a stretched support for oil paint.  I intend on buying a a roll of 100% polyester canvas from a very ubiquitous company.  It is "universally-primed".

    From what I've read, polyester canvas may be less susceptible to some of the humidity/moisture/movement related issues that linen and cotton enact upon an oil paint film.

    Then I read this entry by a moderator:

    Two things first. What is the attraction to polyester as a substrate for you and what type of paint are you planning to use on the polyester? I generally worry about the the overly flexible of polyester for any paint media other than acrylic dispersion paints. Let is know that and in the meantime I will ask some of the other moderators their opinions.

    Baade, Brian

    2016-12-13 21:23:01

    I intended to put a thin coat of lead white ground on top of the acrylic dispersion primer, then paint on it with oil paint.  I thought that if one were to forego panels, then this would be the "best practice" second choice ( with a vented matte- board backing).

    Am I wrong? Is linen or cotton a better, or indifferent, choice?

    I did email the company and they stated no zinc white is used in the priming.

    Thanks for your time and consideration.

    Kevin

  • Question asked 2017-02-24 09:55:55 ... Most recent comment 2017-04-05 10:28:00
    Art Conservation Topics Other Flexible Supports Industrial and Non-Traditional Products
    Question
    How can I make old newspapers less acid for use in my collages.
  • Question asked 2017-04-04 13:42:45 ... Most recent comment 2017-04-04 13:52:00
    Storage
    Question

    ​Do you have any suggestions on how to roll a 10' x 10' oil on muslin painting for storage? My friend acquired the large picture and cannot immediately stretch or hang it and was going to line with glassine and roll over plastic tubing, it had been folded in 10 inch sections. I thought the glassine was a bad idea and wasn't sure about plastic tubing.

  • Question asked 2017-03-31 03:29:55 ... Most recent comment 2017-04-03 16:50:00
    Acrylic Paint Mediums
    Question

    ​I am applying artist acrylic paint diluted approx. 10% with water onto a gesso prepared surface, with a small fine foam roller. The paint is foaming and although I can remedy this eventually, is there a way to prevent the initial foaming? Thanks.

  • Question asked 2017-03-28 08:55:03 ... Most recent comment 2017-04-01 22:02:00
    Acrylic
    Question

    For the underpainting on many of my acrylic paintings, I would like to use more opaque paints​ than most regular acrylic lines provide. 

    There are several products that I've come across -- mostly online but occasionally in the big art stores -- that are described sometimes as acrylic and sometimes as "vinyl." Examples include Lefranc & Bourgeois Flashe Vinyl Paint or Maimeri Polycolor Vinyl Paints. It's hard to tell from the online literature whether whatever it is that makes them "vinyl" would make them incompatible with "regular" acrylics.

    Are these safe to use: (1) as an underpainting for a more traditional acrylic paint (e.g., Golden Heavy Body); and, (2) inter-mixed with those same paints (e.g., to modify opacity)? I'm more interested in (1) but curious about (2).

    Thanks.

  • Question asked 2017-03-14 12:45:43 ... Most recent comment 2017-03-31 16:43:00
    Rigid Supports Sizes and Adhesives Oil Paint
    Question

    ​I'd like to know the accepted, archivally safe way to mount an oil painting created on paper (140 lb 100% cotton) onto a cradled birch panel. Specifically, how to seal the birch so acid cannot migrate to paper, and what no-acid glue to use for mounting.  

  • Question asked 2017-03-31 13:42:04 ... Most recent comment 2017-03-31 14:22:00
    Acrylic Sizes and Adhesives Flexible Supports Industrial and Non-Traditional Products
    Question
    When making things like collages, reliefs or textured paintings, would it be okay to use non-artist paper (for example, tissue paper) if it's first thoroughly coated with acrylic medium? I read that it can be used to preserve things like leaves, so I was wondering whether (aside from being an adhesive) it would stop paper that could be acidic from becoming brittle.

  • Question asked 2017-03-28 15:19:31 ... Most recent comment 2017-03-30 10:12:00
    Health and Safety Oil Paint Pigments
    Question

    ​I have a large oily waste can that contains rags contaminated with lead and mercury (vermilion) based pigments. In order to dispose of them, I will need to dump the waste into a large bag and bring it to a Hazardous waste disposal facility. The can I use has been sitting outside covered for around 6 months, and contains water for combustion concerns. Should I be concerned about any potential metabolic processes that may occur from mold or microbes growing within the rags that could potentially turn Mercuric Sulfide, into a more toxic form of mercury, or any other heavy metal based pigment? If so, what process should I take so that I can dispose of it safetly and not expose myself to these compounds. 

  • Question asked 2017-03-24 18:01:28 ... Most recent comment 2017-03-29 13:35:00
    Acrylic
    Question

    ​Hello! I observed a strange separation of paint/color after leaving the Golden Fluid Acrylic Iridescent Bronze (Fine) in a wet palette overnight. This could be just a colorant added to the mica? It was suggested by a supervisor that I contact you fine folks with this concern! Thank you!! (please see attached photo)

  • Question asked 2017-03-26 13:56:10 ... Most recent comment 2017-03-28 14:18:00
    Oil Paint
    Question

     My usual practice is to start with fresh paint every day - squeezing out just enough of the colours I think i will use for the section of the painting I am working on.  However, there has been discussion recently on several FaceBook forums about saving paint on the palette overnight or even longer - sometimes weeks. The two most common methods seem to be either a) putting the palette in a freezer or b) putting it in a sealed contained each night with a few drops of clove oil on a cloth in that container.  The freezer method seems to be prone to introducing condensation if not handled properly. Both methods will lead to using progressively dried paint over several days or longer. Are these approaches to reducing paint "wastage"  potentially problematic?

  • Question asked 2017-03-23 15:38:06 ... Most recent comment 2017-03-23 16:51:00
    Oil Paint
    Question

    ​Hello,

    I have a bit of dust dried into the top layer of an oil painting I'm working on and would like to lightly sand the surface, remove the dust and sanded particles, then continue with another layer of oil paint.  Should I be concerned with weaking the sublayer?  Thank you!  

  • Question asked 2017-02-11 12:21:09 ... Most recent comment 2017-03-20 16:56:00
    Grounds / Priming Industrial and Non-Traditional Products Rigid Supports Sizes and Adhesives
    Question
    As far as preparing rigid engineered wood surfaces for painting goes, the consensus seems to be that they should ideally be 1. cleaned 2. sanded 3. sized 4. primed. While various websites advise sanding according to preference between subsequent applications of ground to achieve a very smooth surface, what I usually found lacking is the advice of sanding before sizing.
    My questions are as follows:
    1. To clean the surface before sanding, I would use 95% ethanol applied with a rag/kitchen towel. Is this alright? Other options that come to mind are methylated spirits, mineral spirits or hardware store soap, all advertised as pre-paint cleaning agents, but I'm not sure whether they would make a difference and concerned about breathing in the methylated/mineral spirits fumes.
    2. There is generally no information about how hard the surfaces should be sanded - only that they should be sanded "lightly" so that they are lose gloss. The problem is that in order to really remove all visible gloss one has to sand much harder than lightly, so I sometimes have fibers sticking out of my boards after sanding them, which is apparently a sign of sanding too hard. Is there any way of judging how lightly one should press while "lightly sanding"?  Any way of checking other than just running a finger across the surface (possible health risk?)? Also, I understand that a 150 grit sandpaper is a bit too rough and something in the range of 200-250 would be better?
    Finally, is it worth buying an electric sander? I think it might give me a more uniform result, but I'm not sure if it won't be sanding too much even with the lightest touch given the speeds involved.
  • Question asked 2017-02-25 09:41:10 ... Most recent comment 2017-03-20 14:26:00
    Solvents and Thinners Varnishes
    Question
    I forgot to ask in my previous question: in addition to shellac not fully dissolving in a weak formulation, are there other consequences to using a denatured alcohol with a less than optimal percentage of ethanol?
  • Question asked 2017-03-18 22:34:27 ... Most recent comment 2017-03-19 03:41:00
    Sizes and Adhesives Flexible Supports
    Question

    ​Hi,

    I know it is better not to seal the back of your canvas. But what will happen if you stretch reversed primed linen onto you stretcher bars? Is that equally bad?

  • Question asked 2017-03-08 11:44:47 ... Most recent comment 2017-03-15 21:04:00
    Egg Tempera Grounds / Priming Rigid Supports
    Question

    ​i have read the descriptions for how to make real ET paint (fairly easy) and real ET panels with rabbit skin glue and whiting (very laborious).

    I cannot believe that lazy people like me who buy ET in tubes still have to make a panel. Panels with true gesso on are availale from few retailers and are expensive. Sennelier make passing reference to use on canvas with acrylic gesso, but their information is very poor.

    Are you able to offer advice on using these tubed ET paints with commercially available wood panels with acrylic gesso, please?


  • Question asked 2017-03-15 06:53:44 ... Most recent comment 2017-03-15 16:55:00
    Flexible Supports Grounds / Priming
    Question

    ​I've come across conflicting information on this.

    Some old manuals advise us to seal the canvases also from the back to protect them from humidity. Japan size and tin foil were highly recommended to do so.

    On the other hand, I've read that canvases sealed from behind perform worse than canvases where the linen fibers were left to breathe. 

    What is your opinion on this topic?

    Cheers. Nelson

  • Question asked 2017-02-14 13:09:24 ... Most recent comment 2017-03-08 17:26:00
    Acrylic Industrial and Non-Traditional Products Scientific Analysis
    Question
    I am interested in finding a list of Golden Paints  acrylic fluid color density, both fluid and high-Flow, as compared to one another and not to oil or a lacquer based paint. Can you help?
  • Question asked 2017-02-25 09:31:58 ... Most recent comment 2017-03-03 14:52:00
    Solvents and Thinners
    Question
    I make a point of searching out and buying a 190 proof (95% ethanol) denatured alcohol for making shellac.  However many of the denatured alcohols sold at hardware stores contain lesser percentages of ethanol (i.e. a student just asked me about "Sunnyside" brand; the MSDS reveals it is only 86% ethanol).  If someone prefers to buy whatever denatured alcohol is available at their local hardware store, at what percentage number does the ethanol in the formulation become too low to be suitable as a thinner for shellac?

    Also, the MSDS for Sunnyside's denatured alcohol lists "hazardous ingredients", which add up to about 94%.  What is the other 6% or so percent composed of?

    Thanks
  • Question asked 2017-02-27 22:04:58 ... Most recent comment 2017-03-02 11:11:00
    Animal Glue Chalk Grounds / Priming Oil Paint
    Question

    I’m student at an academy of fine arts in Europe. I used to paint on Wood and primed with acrylic gesso from Golden. I recently made the change to canvas and home made ground and that’s where the nightmare began. The priming recipe for oil painting on canvas given by my teacher consists of Rabbit Skin glue, Champagne Chalk (with optional titanium white) and Lindseed oil varnish. I made the first 5 with him and got excellent results but since I have had to make them by myself, I lost a month of painting and so much material because all my primed canvas cracked, I cannot understand why…

    1) I mix 55g of RSG with1L of water overnight in the fridge2)Take one part of that with 2.5 Part of water and do one layer of sizing3) Take on part with 2 part Champagne Chalk with 1 Part water with 1/3 Lindseed oil varnish and use an electric mixer. Then I apply 3-4 coats

    The next day I arrive and everything show mini cracks. I can hear them if I press gentle on the back of the canvas

    I have asked 50 times my teacher and I swear I’m doing what I think he tells me, but obviously something I do is wrong… Do you have any idea what the problem is? do you recommend another method specifically

    I use cotton duck canvas which I stretch. It is for oil painting. I like firm tension but that can take some rough cloth rubbing and handling. Longevity and quality are very important to me.

  • Question asked 2017-02-28 08:31:01 ... Most recent comment 2017-02-28 10:55:00
    Oil Paint Pigments
    Question

    ​I stopped using a newly opened large tube of Windsor and Newton titanium white that I had on hand because it contained "a small amount of zinc" according to the manufacturer. I suspect there is a growing amount of zinc containing paint being abandoned. Obviously, pure zinc white is disocuraegd but it would be great if there was some sort of guidance as to how much zinc is acceptable in a multi-pigment colour. In medicine there is an expression that goes something like "the dose makes the poison". Similarly, I expect that a very small amount of zinc isn't going to cause a problem but I haven't seen any research or guidance as to just what that maximum tolerance for zinc is. Is there any current guidance on this or research that you know of under way to clarify this issue? 

  • Question asked 2017-02-23 12:53:15 ... Most recent comment 2017-02-24 11:51:00
    Rigid Supports Sizes and Adhesives Grounds / Priming
    Question
    When applying a glue size to a fibreboard (MDF) panel, does the strength of the glue need to be stronger than the quantity of glue mix used in gesso?  I have been advised by my supplier to use a stronger formula for the inital sizing (1:10) but I haven't found this advice anywhere else.
  • Question asked 2017-02-21 17:04:22 ... Most recent comment 2017-02-21 17:48:00
    Drawing Materials Dyes Environment Ink Paint Making Pigments
    Question
    Hello! I'm a painting and drawing senior BFA student at the School of the Art Institute of Chicago and was wondering if you have any information or insight on residencies, workshops, or any opportunities that will allow me to engage in foraging and collecting my own materials, extracting organic pigments, making my own inks and paints, etc. Anywhere in the world! I hope to turn this into a fulbright scholarship application, so anywhere you suggest will help!

    I am interested in organic material, traditional processes, smaller communities and working in the natural environment... And of course, something very immersive. Even paper-making and natural dye techniques are helpful suggestions, but I'd love to just make materials from scratch. Thank you so much for your help!!
  • Question asked 2017-02-21 14:07:43 ... Most recent comment 2017-02-21 15:36:00
    Egg Tempera Rigid Supports
    Question
    To minimise warping when painting with ET on large panels 2ft x 3ft  (12mm MDF), I have previously gessoed both sides (8 layers or so) of my panels after a coat or two of rabbit skin size.  However this is a laborious technique owing to the drag of the gesso on such large panels.  Can I apply rabbit skin glue instead (8-10 layers) which glides on much more easily.  I am not inclined to brace/bracket my panels so any advice on alternative methods of stabilising large panels would be most welcome.
  • Question asked 2017-02-16 16:34:18 ... Most recent comment 2017-02-16 17:47:00
    Flexible Supports Acrylic
    Question
    Is Tyvek a sustainable surface for an acrylic painting?
  • Question asked 2017-02-16 16:36:53 ... Most recent comment 2017-02-16 17:47:00
    Drawing Materials Varnishes
    Question
    What's the best brand/material to fix a pencil on Canson drawing paper? I've used sprays before, just interested in what others are using. Thanks.  
  • Question asked 2017-02-14 22:43:54 ... Most recent comment 2017-02-15 10:41:00
    Oil Paint Paint Mediums
    Question
    I was wondering how much medium one could safely add to glaze layers.I remember the question being asked years ago on the old AMIEN forum, and there didn't seem to be a clear-cut consensus. One reply suggested that the ratio almost didn't matter, as long as the glaze was applied thinly enough. In the opinion of the moderators, how much leeway do we have regarding the amount of medium in very thin glazes? Let's say we have a glaze which is half paint, half medium, brushed on then patted down with a sponge - basically tonked - leaving more or less a residual stain of colour. In a glaze layer this thin, is the high amount of medium likely to cause any problems? I'm assuming if yellowing is a problem with oiling out, it might be something to worry about here too. And could we expect several ( similarly extra-thin ) layers of glaze, applied over each other, to develop the same problems that a single, thicker layer of medium-heavy glaze might, yellowing or even wrinkling? As always, any advice would be greatly appreciated.
  • Question asked 2017-02-15 08:19:14 ... Most recent comment 2017-02-15 10:40:00
    Egg Tempera Matting, Framing, and Glazing
    Question
    Egg Tempera artists are sometimes told to frame work under glass, to protect the initially vulnerable surface of tempera from scratches.  Both tempera's ground (traditional gesso) and support (wood-based panel) are hygroscopic.  Does framing egg tempera under glass protect the work from ambient moisture, or is glazing more likely to trap moisture, potentially leading to mold, delamination, etc.? 

    Thanks,

    Koo Schadler
  • Question asked 2017-02-14 14:53:57 ... Most recent comment 2017-02-14 15:01:00
    Art Conservation Topics Gilding Matting, Framing, and Glazing
    Question
    I gild the bevels of my archival mat boards, and I am wondering if this affects their archival-ness.  I use acrylic paint, water-based size, and 23K or other genuine gold leaf.
  • Question asked 2017-02-14 13:19:10 ... Most recent comment 2017-02-14 14:22:00
    Acrylic Industrial and Non-Traditional Products Scientific Analysis
    Question
    Regarding my question about a comparison of the Density of The fluid paints, I am mixed media and collage artist and use pours. I would like to have more control by knowing this simple fact.
  • Question asked 2017-02-13 16:26:34 ... Most recent comment 2017-02-13 17:53:00
    Grounds / Priming Rigid Supports Sizes and Adhesives
    Question
    I plan on painting on rigid, absorbent supports (HDF/MDF/hardboard etc.). Is it okay to speed up the drying time of PVA sizes and acrylic dispersion grounds using a hair dryer? Specifically, is it okay to:
    1) Speed up the drying time of the size before applying the next layer?
    2) Speed up the drying time of the ground before applying the next layer?
    3) Speed up the drying time of the ground before painting?
    In any case, how long should I wait before starting the next step/how do I know that the layer is dry enough? I have read the 24 hours drying time recommendation for acrylic ground before beginning a painting, but are there any estimates for the rest?
  • Question asked 2017-02-10 12:14:42 ... Most recent comment 2017-02-10 12:35:00
    Grounds / Priming Industrial and Non-Traditional Products Rigid Supports Sizes and Adhesives
    Question
    It appears there are conflicting recommendations on various manufacturers' websites regarding sizing HDF/MDF before applying acrylic ground. Looking at the table in the "Adhesives and Sizes" document, three coats of acrylic ground should be enough to protect from any noticeable migration of mediums or solvents through the support, so shouldn't it also be sufficient to protect the work from the chemicals that might migrate from the support?
    Assuming that sizing is still recommended, should PVA glue with a pH of 7 suffice? If so, should it be diluted? How much?
    Also, when using HDF/MDF that's laminated on one side, is it fine to leave the laminate as is, since it's already a protective layer?
  • Question asked 2017-02-09 18:00:49 ... Most recent comment 2017-02-09 18:45:00
    Paint Mediums
    Question
    I work in oils and would like to know the best choice for a medium when i am painting alla prima.  I only feel the need for a tiny amount of medium if I feel the paint directly out of the tube is too stiff, otherwise, I don't use it.  Should i use straight linseed oil, straight stand oil, a dilution with OMS of either of these, or somehing else?  I am not looking for something to make the paint dry faster.  Thanks in advance.  
  • Question asked 2017-02-09 07:07:14 ... Most recent comment 2017-02-09 10:39:00
    Grounds / Priming Industrial and Non-Traditional Products
    Question
    Given that I've heard from many people that exterior acrylic paints (hardware store ones) perform quite well as a ground for oil/acrylic paintings, and that "artist's gesso" is very expensive and hard to obtain where I live, I would like to ask for expert advice regarding their use.
    I have read the "Myths, FAQs, and Common Misconceptions" section on industrial/outdoor products, but the claims made there are very vague an nebulous. "can potentially lead to problematic consequences" and "Some of these additives are known to eventually migrate out of these commercial paints after a certain period of time" sound more like marketing claims made to instill fear and uncertainty, especially since they do not cite any works published in scientific, peer-reviewed literature. One could just as well make an argument that since none of the manufacturers of artist materials release their full formulations, those could just a well produce similar problems.
    Therefore, aside from this clarification, I would also like to ask about recommendations for ground alternatives for engineered wood (specifically HDF and MDF).
  • Question asked 2017-02-05 17:39:35 ... Most recent comment 2017-02-05 17:43:00
    Flexible Supports
    Question
    What is the very best way to tighten a stretched canvas ( no keys, rigid stretcher frame) ?  I have  just stretched a 40 x 48 canvas with  an excellent tight "thong" sound when finished ( one week ago). Now, it has relaxed - no sags, nor pulls- but just not as tight as I like to paint on. ( info: Fredrix's Dixie 123, acrylic pre-primed roll) THANK YOU for your kind reply in advance.
    Nancy
  • Question asked 2017-02-02 09:43:44 ... Most recent comment 2017-02-02 17:29:00
    Oil Paint Varnishes
    Question
    I understand that there may be a temporary yellowing of a fresh paint film, if it is stored in the dark, which is reversible with the application of sunlight, and there is a more long term, permanent yellowing that occurs over decades, if not centuries.____Isn't this long term yellowing due more to the aging of damar, copal, or other or other varnishes used in  or on  the top of the paint layer than to the drying oil used in the paint layer?_____Thanks for your thoughts.___Richard
  • Question asked 2017-02-02 13:41:33 ... Most recent comment 2017-02-02 15:55:00
    ASTM Drawing Materials
    Question
    I have noticed a lot of my favorite contemporary artists, like Colleen barry and Scott Waddell, make use of these prismacolor color pencils, for some pretty exceptional work. I question the durability of the material though. Prismacolor does not have a chart on this line of pencils. Specifically,
    Carmine red
    Scarlet red
    Vermilion
    Tuscan red
    Terra cotta
    Brown
    Black
    Tuscan red
    Terra cotta
    Brown
    Black
    I know the cpsa has their workbook, but I am a very poor artist and don't have 45$ currently.
  • Question asked 2017-01-31 09:37:19 ... Most recent comment 2017-01-31 16:08:00
    Alkyd
    Question
    Recognizing the increased flexibility and speed of drying in alkyd paint films over linseed oil/stand oil paint  films...

    1.   Would you recommend the use of alkyd mediums or alkyd paints over traditional oil mediums and paints for the most permanent, strong, flexible, non cracking and non-yellowing paint film?

    2.  What are the disadvantages of alkyd mediums, if any?

    3.  As alkyds in artist oil paints are only a few decades old, how confident are you that alkyd mediums will continue to out pace oil mediums in producing superior paint films?

    4.  To minimize the use of driers, would it be advisable to seek an alkyd synthesized from drying oils, linseed or walnut, vs non drying oils, safflower, soy, sunflower, etc?

    Thank you so much for your expertise.

    Richard
  • Question asked 2017-01-31 11:51:09 ... Most recent comment 2017-01-31 16:07:00
    Drying Oils Alkyd
    Question
    How does a walnut oil film compare with a linseed oil film in strength and flexibility?......   I know that it is a slower drying oil and will eventually reach the same level of yellowness and embrittlement over the course of decades as linseed, but will take longer to do so.......  I am considering the use of a walnut alkyd, added to a walnut oil medium to compensate for the slower drying time of the latter. .... .. The lower viscosity of both, vs stand oil with an added alkyd medium, would then require less OMS to thin it out, resulting in reduced solvent evaporation in an enclosed studio.   (I live in MN.   Either the heat is on or the air conditioning, ha, ha)....   Walnut oil is also drying oil and I suspect that a walnut alkyd may use less drier in manufacture than those alkyds made from semi-drying oils....Thank you for your thoughts....Richard
  • Question asked 2017-01-26 21:34:58 ... Most recent comment 2017-01-29 16:27:00
    Sizes and Adhesives Rigid Supports
    Question
    pva size for birch panel?
  • Question asked 2017-01-29 10:47:47 ... Most recent comment 2017-01-29 12:41:00
    Alkyd
    Question
    1.  Is the speed of drying in alkyd mediums and paints due to the chemical nature of of the alkyd compounds themselves, or are driers usually added to achieve their drying speed?

    2.   I understand that not all alkyds are created equal, being synthesized from different oils.   Do some alkyd mediums form stronger, more flexible paint films than others?  (In other words, are they all equally good in forming a reliable paint film?)



    I'm trying to avoid excess driers, as they tend to promote cross linking of the paint film indefinitely (faster embrittlement), but wish to speed up the drying time  of titanium white to be comparable to cremnitz white, which I may abandon use of because of cost.   Was thinking of using a small amount of alkyd medium in a stand oil medium to compensate for the slow drying time of titanium,  i.e. 10% alkyd, 30% stand oil, 60% OMS.

    Thank you for your insights,

    Richard

    PS   I dislike being held hostage to the much higher cost of cremnitz white and am seeking the next best alternative for painting landscape on panels.   I will miss cremnitz, however.
  • Question asked 2017-01-26 18:01:16 ... Most recent comment 2017-01-27 01:20:00
    Flexible Supports Other
    Question
    Hi, would you recommend coating a new wood stretcher with a coating of some kind, such as a water-borne polyurethane to seal the wood? Should I be concerned about volatile emissions from the bare wood on my cotton or linen canvas over the long term? The stretcher bars are bevelled. Thanks.
  • Question asked 2017-01-26 21:34:15 ... Most recent comment 2017-01-27 01:18:00
    Question
    birch support
  • Question asked 2017-01-26 10:01:22 ... Most recent comment 2017-01-26 10:11:00
    Oil Paint Pigments
    Question
    With concerns regarding the use of any quantity of zinc white and the increasing use of safflower and walnut oil as a binder in white oil paint, what alternatives, if any, do we have to purchase a good film forming white as an alternative to the increasing unaffordable lead or cremnitz white?

    Safflower, walnut and poppy oil are not thorough driers, zinc becomes brittle and apparently affects both titanium and lead white when used in any quantity, titanium creates a "spongy" paint layer that is not tough, but cremnitz white is increasingly unaffordable or contains one of the above oils above or zinc, in some cases.   Any recommendations?   Which poor alternative do I choose?

    PS  I paint on panels and use stand oil as a medium, with lead white, so that film toughness and flexibility are maximized on an inflexible support.

    Thank you for your insights.

    Richard


  • Question asked 2017-01-24 12:43:49 ... Most recent comment 2017-01-24 13:55:00
    Chalk Drawing Materials Pencil
    Question
    I am curious about what the white chalk of the old masters was made of, and where it might be found today. Currently I use generals white charcoal pencil, which I believe is some proprietary blend, and am curious about its lightfastness. I contacted generals but have yet to hear back.
  • Question asked 2017-01-21 10:10:27 ... Most recent comment 2017-01-21 10:35:00
    Art Conservation Topics Flexible Supports Mural Painting Oil Paint
    Question
    What is the better/best painting support for large scale easel painting (Las Meninas or The Raft of the Medusa come to mind)
    I personally find myself between a rock and a hard place when it comes to large scale painting supports. As many of these forums have explained, the hard panel surface is far more structurally sound than its canvas/linen counter part. On the other hand, when you want to create painting larger than sheet material size, the seam will undoubtedly rear its face during the life of the painting. I realize there are also ways to join boards to make a larger sheet surface, but my gut tells me those seams could cause problems down the line, as well. There may not be an ideal surface, but is there a best surface for this endeavor?
  • Question asked 2017-01-20 11:09:48 ... Most recent comment 2017-01-20 11:33:00
    Art Conservation Topics Pigments Scientific Analysis Technical Art History
    Question
    I have the good fortune to have acquired an 18th century British family portrait.  The painting has an inscription that dates it to 1754.  I am taking X-sections in hopes to study the layer structure, pigments and possibly help with an artist attribution.  The work is unsigned but similar to other works by Arthur Devis a British portrait painter who was active in London at the right time.  As I rarely work on paintings that are not American 19th century works I welcome any advice or insight.  I do have sampling opportunities in many different colors in the painting (according to areas of loss). 
    Thank you in advance
    Nina Roth-Wells
  • Question asked 2017-01-19 10:25:33 ... Most recent comment 2017-01-19 11:45:00
    Technical Art History
    Question
    Deseo saber sobre composición,materiales materiales en las obras de arte victoriano sobre todo en John w. Waterhouse.
  • Question asked 2017-01-17 08:43:08 ... Most recent comment 2017-01-17 08:53:00
    Egg Tempera Other Rigid Supports
    Question
    1. Does shellac discolor with age?  I’ve read both that it’s photostable (whatever degree of yellow is present when it’s initially made, depending on the cut, does not change over time) and also that it gets more yellow with age.   I have a 18 year-old test strip that shows no color change so far, but perhaps that’s not long enough to say.  Has there been testing on the yellowing of shellac?

    2.  My understanding is that shellac gets brittle with age.  If I’m using it as an isolating layer on tempera (which also gets brittle with age) on a panel, does the solidity of the support address this concern?  Or is brittleness always a concern, regardless?

    3.  I believe shellac becomes increasing resistant to solvents as it ages – is this irrelevant if its purpose is to isolate?  In the case of isolating, could this be a sort of benefit, like a paint film curing and becoming insoluble, so to speak?

    Thanks as always for your help.  Koo Schadler
  • Question asked 2017-01-09 16:55:26 ... Most recent comment 2017-01-09 17:13:00
    Drawing Materials Storage
    Question
    I have a growing stack of drawings on paper in graphite, charcoal, conte.   Is it really necessary to  interleaf the drawings? And is Tyvek the best material for these types of media? If you're on the site it says glassine is not good for long-term storage and mylar has electro static charge so I'm just wondering how I can store my drawings. Thanks.
  • Question asked 2017-01-07 17:03:07 ... Most recent comment 2017-01-07 17:24:00
    Oil Paint
    Question
    Is it safe to apply fresh paint over or into a layer of paint that has begun to set and has become tacky? Is it safe to blend tacky paint? Can either of these cause adhesion problems, etc.? No medium is being used, only a little bit of solvent.
  • Question asked 2017-01-07 13:13:02 ... Most recent comment 2017-01-07 13:16:00
    Question
    What is opinion of conservators and specialist about paint with oil colors on acrylic gesso. Will have problems and delamination for oil colors after years ? Thank you .
  • Question asked 2017-01-07 13:09:59 ... Most recent comment 2017-01-07 13:15:00
    Industrial and Non-Traditional Products Oil Paint Studio Tools and Tips
    Question
    Dear all, I am facing a problem. I am an art reproduction specialist, and until now I have been making all of my canvasses, from stretching on the frame, to prime grounding. I had done only one medallion in my career, and with success. It was longer than stretching a canvas on a square frame, but it wasn't that difficult. There were no folds, and I used tacks. I recently had a new order with a medallion format, and to save myself some time, I tried ordering to a national specialist a handcrafted but ready-made medallion canvas. I was shoked to receive it, first in only a thin cellophane wrap, but worst is, the cloth was stretched with staples, onto the back. Also the staples were put very close to one another, it felt like the number was too much, and they were not regularly applied. As a conservator too, and being aware of the quality of the materials I use, I find this outrageous.
    I called the craftman to complain but he assured me during an hour that nobody ever complained, that that's how it's done, never in is career anyone said otherwise, and should I have wanted tacks instead of staples I should have asked. Now, again, this company is specialized in traditional, handcrafted canvasses, and their clients range about all the national museums.
    I am lost here, what are your hints on the subject ? Am I to idealist to ask for tacks on a medallion canvas ? He said this would not have allowed to avoid folds entirely, but again, I did one myself with success. What do you think, do museums allow art reproductions to be made in these conditions ? Thank you again for your answers.

    S.G
  • Question asked 2017-01-06 17:14:48 ... Most recent comment 2017-01-06 17:20:00
    Acrylic Flexible Supports
    Question
    Hi, What kind of issue can I expect if applying acrylic paint on Color-aid paper? It will be adhered to cold press illustration board.  Thanks
  • Question asked 2017-01-06 13:31:16 ... Most recent comment 2017-01-06 13:32:00
    Matting, Framing, and Glazing Other
    Question
    Hello! I would like to know what is the best way to record what materials I used (pigments mediums and varnishes on the back of the canvas) I was thinking about going to a printshop and getting this info printed on canvas and gluing this small patch to the back of the artwork, but i am afraid this might disfigure the artwork down the line, same with using permanent markers. I will appreciate your input and help! Thanks!
  • Question asked 2017-01-06 12:24:16 ... Most recent comment 2017-01-06 12:30:00
    Flexible Supports Acrylic
    Question
    Hi, I have 84x30 inch canvas that is sized and primed, Gamblin PVA and Oil Primer. It is stretched on those 1x2 so called gallery stretchers. No matter how tight I try to stretch it I still get a wobbly bounce after each brush stroke. Is it safe to apply GAC 400 the back of the canvas to try and stiffen it up and reduce the movement, The stretcher can't be keyed. Thanks.
  • Question asked 2017-01-03 13:54:46 ... Most recent comment 2017-01-03 16:17:00
    Grounds / Priming
    Question
    Hello, I would be interested in knowing what you use for priming on canvasses, what are your recipes and ways of applying ? Precisions on century accuracy and references would be very much appreciated ! Thank you in advance for sharing your discoveries and works on this very basic but fondamental subject.
  • Question asked 2017-01-01 13:43:55 ... Most recent comment 2017-01-02 09:39:00
    Egg Tempera Pigments Paint Making
    Question
    How do you grind lead white? It seems to float on the surface of the water.
  • Question asked 2017-01-01 14:23:56 ... Most recent comment 2017-01-02 09:39:00
    Egg Tempera Gilding
    Question
    Can you place gold leaf over an area that has been painted in egg tempera?
  • Question asked 2016-12-28 19:10:49 ... Most recent comment 2016-12-28 19:17:00
    Egg Tempera Varnishes
    Question
    I have been experimenting with varnishing egg tempera paintings and have several questions I’d like MITRA’s input on.

    1.  As with oil, it’s generally presumed best to wait until a tempera painting has polymerized before varnishing (understanding that polymerization is dependent on number and thickness of layers, drying conditions, etc.)   Polymerization in ET seems to me to occur within 3 to 6 months; to test I either polish the surface (cured paint has a certain feeling of hardness) and/or carefully wipe a corner with a damp rag (the water beads up, no paint lifts).  These ideas come from my experience, not from any definitive timeline or test from a conservator.  Is there consensus on how long it takes, more or less, for an egg tempera painting to cure, and how to test for polymerization?  

    2.  Having spent a couple of decades experimenting with varnishing tempera, I’ve come to believe an isolating layer is necessary (at least on a relatively new tempera; it may be different for a centuries-old painting).  In my experience an egg tempera surface, whether a day or year-old, is still absorbent enough (because of high PVC) that varnishes sink in to varying degrees.  Since any layer applied directly atop seemingly becomes linked with the underlying paint, it seems best to first cover the tempera with a very thin layer of an isolator (I’ve experimented with casein, shellac, B72, Golden’s GAC500 & Gel Medium, Laropal, PVA both water and acetone based), then put a reversible varnish on top of the isolator.   This allows the varnish to go on evenly, stay distinct from the paint layers, and be reversible.  Your thoughts?

    3.  If the above is true – it works best to isolate a tempera before varnishing – does it matter how long the tempera has polymerized before applying the isolator (since the isolator becomes linked with the paint regardless of the paint’s age)? 

    Well, I have more questions, but that’s enough for now!

    Thanks,

    Koo Schadler
  • Question asked 2016-12-27 13:10:38 ... Most recent comment 2016-12-27 17:53:00
    Acrylic
    Question
    Hi,
    I'm a painter using acrylics and am thinking about incorporating wax medium (typically geared towards oil paint)  into the acrylic paint. Will the wax medium merge well with polymer based paint?
  • Question asked 2016-12-26 14:40:03 ... Most recent comment 2016-12-26 16:05:00
    Acrylic Flexible Supports Art Conservation Topics
    Question
    I have a very tiny (1/4") tear (slit) in an acrylic on canvas.  Is there a way to safely repair this?
  • Question asked 2016-12-24 12:25:56 ... Most recent comment 2016-12-24 17:21:00
    Egg Tempera Grounds / Priming Rigid Supports
    Question
    I have a few questions about SID (support induced discoloration) relative to traditional gesso and egg tempera.

    1.  The “Rigid Supports” article posted on this website, when discussing hardboard, says “SID will occur if the oily or resinous material migrates through the size or seal and and stains the ground or paint layers”.  My understanding is that oils and/or resins in or atop engineered wood-based panels are stable and cannot move or migrate – they are polymerized or cured and can’t go anywhere.  Yes, no?

    2.  My understanding is that SID is caused by materials in the wood itself (tannins, dirt, sap, starches), drawn up into the gesso by water based grounds and paints.  Yes, no?

    3.   Has there been testing to see if SID occurs in a traditional gesso ground and/or egg tempera?  I’ve done a couple of tests myself (painting a word on a panel using GAC 100, applying traditional gesso all over, seeing if the word later appeared) - very little to no SID appeared.   Could the very high solid content (percentage of chalk) in traditional gesso inhibit SID? 

    4.  The various products for blocking SID (Archiva-seal, GAC 100, PVA) are all polymer based and designed to sit under acrylic or oil grounds, not traditional gesso. I tried a crosshatch adhesion test of traditional gesso atop GAC 100 and adhesion was not great.  If SID is a concern with egg tempera, any ideas for how to block it?   I presume a layer of cloth applied with PVA to a engineered panel would do it, but is there a simpler option?

    Thanks!

    Koo Schadler
  • Question asked 2016-12-23 16:02:53 ... Most recent comment 2016-12-23 16:42:00
    Rigid Supports Oil Paint
    Question
    I just asked about painting oils on birch plywood, which I do directly, no primer. To see an example go to www.bowerart.com> galleries> painting and click on the thumbnail at the bottom left of a man in a blue sweater. That is an example. you can see the raw wood of the plywood. The painting is 2or 3 years old an looks like the day I painted it. Will it hold up for 500 years?
  • Question asked 2016-12-23 15:50:16 ... Most recent comment 2016-12-23 16:39:00
    Question
    Is it archival? I have painted on quarter inch birch plywood and like it a lot. i like the mid tone, surface, absorbency, durability, light weight, price and it has never shown a problem. I sometimes do not even seal it but paint right onto it, never a problem so far. Some opine that over time the oils will do this and that especially without priming, much like with canvas. Some say ue "marine" plywood only. Anybody?
  • Question asked 2016-12-21 21:28:35 ... Most recent comment 2016-12-22 13:11:00
    Drawing Materials Flexible Supports Industrial and Non-Traditional Products
    Question
    There are a lot of artist starting to use terraskin as a paper alternative particularly those doing metal point.  Their website explictly says that the stuff is designed to degrade under "the right environmental conditions" of heat, moisture and UV light.  For this reason it seems to me very risky to use.  Others argue that if kept indoors and protected from UV light it should be fine.  I don't think once an artist sells a piece of work that they have any control over how it is displayed.  Could you please weight in about the potential longevity and issues of these stone "papers" for fine art work?
  • Question asked 2016-12-21 13:06:33 ... Most recent comment 2016-12-21 14:31:00
    Oil Paint
    Question
    Are there good ways to prepare a layer of paint for overpainting that has become overly oily or slick?  Sanding with coarse sandpaper still leaves a surface that squeaks if I rub my finger across it.
  • Question asked 2016-12-18 02:22:48 ... Most recent comment 2016-12-18 11:22:00
    Oil Paint
    Question
    How can we best paint slowly to get a good structure in the painting? Meaning indirect painting such as subsequent corrections, revising the design, altering a colour,  glazing, scumbling (when you want the lower layer to be firm enough not to lift but you want to do it as soon as possible) or adding finishing details in fatter paint?

    Beyond starting with thin fast drying pigments or fast dry modified matte paints and observing critical pigment volume or fat. Beyond that, we mix different pigments with different drying times and change our minds. Which pigments are notorious for moving more as they dry? As a general guide for an average situation (knowing there are multiple variables including pigments and additions, weather and ground) how long is too short? eg skinned over paint that's still wet below shouldn't be painted over as it's still in it's active phase of weight gain and loss as it dries (is this typically 3-4 weeks for a thinnish, moderate drying time pigment in linseed oil with no driers or alkyds added?) How long should we wait before painting on top of a painting in progress? thank you
  • Question asked 2016-12-18 03:16:44 ... Most recent comment 2016-12-18 05:03:00
    Matting, Framing, and Glazing Rigid Supports Sizes and Adhesives
    Question
    Hello, I want to glaze (plexiglas) my paintings. What kind of rigid panel should I attach the canvas to that doesn't hold too much moisture beneath the finished painting? Hardboard is heavy and can warp. ACM can be expensive or tricky to glue canvas to. Does glueing the linen to the support using acrylic medium attract extra moisture?  Will framing behind glazing restrict the oxidisation of the paint? How much space is needed between the glazing and the painting and a rear board?
  • Question asked 2016-12-16 15:56:21 ... Most recent comment 2016-12-16 16:13:00
    Art Conservation Topics Egg Tempera Mural Painting Solvents and Thinners
    Question
    I'm trying to develop some glazing techniques to use on egg tempera paintings. I need to slow the drying time down. How should I go about this ?
  • Question asked 2016-12-14 23:46:43 ... Most recent comment 2016-12-15 00:03:00
    Question
    I mostly use GAC 700 and Specialty Polymers BH61 because I like their clarity when dry.  They both have very high solids content.  While they seem similar in many regards they are very different in their tackiness when dry.  GAC 700 is very tacky and BH61 is very hard.  I notice GAC 700 will be flexible soon after it is dry but BH61 will take weeks to become flexible.  After they are fully cured both can be bent completely over without breaking.  I wonder if the "gumminess" of GAC 700 occurs because it is made to be flexible sooner and if this occurs by an additive that creates the stickiness of the final film and what that additive might be?   I have tried propylene glycol but I don't think that is it.   Also I notice that BH61 will sometimes form fine cracks (not fissures) in certain drying conditions and I wonder if this is related to the tackiness?
  • Question asked 2016-12-14 18:30:40 ... Most recent comment 2016-12-14 18:34:00
    Rigid Supports
    Question
    I don't know if this is proper on this site to ask for the names of companies that offer already sized and primed canvas or linen mounted onto rigid supports that are archival and do not contain zinc white? I don't like to spend my time preparing supports. I know they will be more expensive when already prepped but it does save a lot of time even though I may still add another coat of oil ground or acrylic ground on top.  Thank you.
  • Question asked 2016-12-14 11:19:45 ... Most recent comment 2016-12-14 18:16:00
    Oil Paint Pigments
    Question
    Some paints are fast drying but have a high oil content to pigment ratio out of the tube.  Is it safe to use these in an underpainting?
  • Question asked 2016-12-13 19:44:14 ... Most recent comment 2016-12-13 21:14:00
    Flexible Supports Grounds / Priming
    Question
    I'd like to try painting on polyester canvas. Unfortunately, it's difficult to find artist polyester canvas where I live; equally difficult is getting untreated, "loomstate" polyester fabric. Easy to find, though, is polyester canvas for inkjet printing, and plain polyester canvas from the fabric store. My question is, are either of those an acceptable substitute, and safe to prime with acrylic gesso? I'm concerned that washing the canvas wouldn't properly remove the coatings it would have, causing adhesion problems for the gesso. Perhaps it would be be wiser to stick with cotton and polycotton canvases, made for artists, until a source for artist polyester canvas becomes available? Thank you.
  • Question asked 2016-12-12 06:24:22 ... Most recent comment 2016-12-12 11:55:00
    Handling and Transportation Oil Paint
    Question
    What is the best way to clean a dusty oil painting? Can I use a tack cloth? Should I pour water and wipe it off?
  • Question asked 2016-12-11 23:49:07 ... Most recent comment 2016-12-12 03:08:00
    Alkyd Drying Oils
    Question
    Do different paints with different oil binders, bond as strongly together as paints with the same oil binder? And does this apply to alkyd/oil bonds, considering alkyds are often derived from oils other than what is used as a binder in oil paint?
  • Question asked 2016-12-11 23:16:22 ... Most recent comment 2016-12-12 03:07:00
    Oil Paint
    Question
    How important is using pigments of low oil content in the underpainting for adhesion of later layers? I've had problems with adhesion, even when there was sufficient tooth in the underpainting, the overpainting can be peeled or scratched off easily to reveal the first layer.  I realized after that the Titanium White I used in the underpainting was especially oily, and the overpainting white I used was not.
  • Question asked 2016-12-11 22:56:34 ... Most recent comment 2016-12-12 03:06:00
    Oil Paint
    Question
    Is oiling out necessary for good adhesion between paint layers? If the layer is sunken in or matte, does it need to be oiled out? 
  • Question asked 2016-12-11 23:05:28 ... Most recent comment 2016-12-12 03:06:00
    Alkyd Oil Paint
    Question
    Is it safe to overpaint an alkyd/linseed paint with linseed paint?  These Gamblin Faste-Matte paints have a calcium carbonate additive to help with adhesion, but I am worried about varying degrees of flexibility between paint layers, especially because I use a lot of linseed Titanium White in the overpainting.  If not, is there a white you would recommend for underpainting?
  • Question asked 2016-12-10 19:33:02 ... Most recent comment 2016-12-10 19:42:00
    Grounds / Priming
    Question
    I have been instructed to use Shellac on Marine Plywood for a panel to paint on. The Shellac is obviously to seal the wood, but how do I get the ground to be white? Do I gesso the wood first?. Do I apply Gesso on the Shellac? do I mixe the Gesso WITH the Shellac? Once it is Gessoed, do I also need to put some kind of an Oil Paint Ground on it? I don't really like to do the prep work, I prefer someone else do the material preparation and I can just paint. I can't seem to get what I need pre-prepared however so my next wish would have been an all-in-one spray to make short-shrift of the work, but that doesn't appear to be available either.   POST SCRIPT: I actually asked this elsewhere and the artist who made the suggestion to me answered, knowing the effect I was after and said that I don't need any white or gesso at all to get the affect that I want.  The Shellac is intended as a sealer on the wood that is not too slippery or absorbent to paint on and to  allow the wet , streaky brush marks I am looking for, with the apricot wood color coming through.    However, what if I DO want the ground to be white?  Do I tint the shellac itself with lead white oil paint, Gamblin oil Ground, or Titanium White Oil?
  • Question asked 2016-12-09 09:16:08 ... Most recent comment 2016-12-09 10:34:00
    Oil Paint Paint Mediums Varnishes
    Question
    When using Oleogel as a medium, does the wax in Oleogel pose an issue to safely cleaning the painting in the future? Or create issues with the longevity of the painting by making it more susceptible to heat or other issues?
  • Question asked 2016-12-07 20:08:20 ... Most recent comment 2016-12-08 01:39:00
    Flexible Supports Storage Industrial and Non-Traditional Products Other
    Question
    Along the question about 'Terraskin', I want to know more about 'Tyvek'-- I have seen it used in a few installations recently, in sculptural applications. Other than the convenience and weight factor (compared to an actual heavy sculpture), what are your thoughts about its use? Best practice?

    And can this be adhered to canvas for dimensional effects? If yes, what did you use to adhere and how would you protect it for the future?
  • Question asked 2016-12-02 15:48:08 ... Most recent comment 2016-12-07 11:03:00
    Flexible Supports
    Question
    I have several used linen canvases which, rather than throwing away, I would like to reuse. Is this possible? Thanks in advance
  • Question asked 2016-12-04 14:37:35 ... Most recent comment 2016-12-07 11:03:00
    Oil Paint
    Question
    I am painting with Old Holland oil paints using a small amount of linseed as a medium, on linen canvas. My painting sometimes take several weeks to reach the first stage in completion. After that period I sometimes need to make small changes. At what point after the initial painting has been completed is it too risky to continue adding more changes? For example if I  'finished' a painting, could I then return to it six months after to make a change either a glaze or further painting?
  • Question asked 2016-12-04 15:32:55 ... Most recent comment 2016-12-07 11:03:00
    Grounds / Priming Oil Paint Rigid Supports
    Question
    I have some hairline cracks in my true gesso ground, im wondering if these will continue to get bigger and perhaps crack subsequent layers of oil paint. 
  • Question asked 2016-12-05 12:30:39 ... Most recent comment 2016-12-07 11:03:00
    Other Studio Tools and Tips Art Conservation Topics
    Question
    What´s the best way for a signature at the back of the canvas that wouldn´t eventually penetrate through the ground and paint layers and thus affect the face of the painting - become visible? (Size of the signature; how to dillute paint - oil (if at all) or acrylics that the color would flow freely in order to paint a signature on the unprimed/raw side of the canvas? Use of other dry mediums like chalk, graphit, pastel?) Thank you!
  • Question asked 2016-12-05 15:49:00 ... Most recent comment 2016-12-07 11:03:00
    Pastel Health and Safety
    Question
    Are there any health hazards when blending pastels with bare hands?
  • Question asked 2016-12-06 09:52:42 ... Most recent comment 2016-12-07 11:03:00
    Pigments Paint Making Paint Additives Paint Mediums Other
    Question
    Every now and then, I have to make conductive paint with my students. Up until now, I do it with graphite and acrylic binder, which sort of works. Sort of, because the acrylic is an insulator. So basically what I am doing now, is to underbind the paint, so it still conducts current.
    I know there are conductive binders though. Ulysses Jackson from Golden suggested polytiophene as a conductive binder, but I cannot find it anywhere. Does anyone know if there is another conductive binder that could work?
  • Question asked 2016-12-07 10:11:57 ... Most recent comment 2016-12-07 10:57:00
    Animal Glue Art Conservation Topics Drying Oils Flexible Supports Gilding Grounds / Priming Oil Paint Paint Making Pigments Rigid Supports Sizes and Adhesives Technical Art History
    Question
    I am searching for information on the use of red bole in oil painting. My understanding is that it is a clay [primarily used in building at this point] that can be diluted to cream consistency, mixed equally with warmed RSG, and applied over traditional gesso for toning a surface. Setting aside the structural debates of stretched linen/canvas surfaces, how can one use this over such a surface. Are there any pigments that approximate this clay, or is there an oil ground approach that provides a comparable alternative? Thank you for any time or considerations.
  • Question asked 2016-12-05 18:01:07 ... Most recent comment 2016-12-05 18:42:00
    Casein Flexible Supports
    Question
    In the resources here, in the Grounds and Primers PDF, it states that casein should only be used on rigid supports because it is brittle.
    However, at the site http://www.richesonart.com/products/paints/richesoncasein/richcaseinfaq.html, it states
    "Can Casein be used on stretched canvas?
    Yes, but you must remember to paint very thin because Casein can crack if it's applied too thickly. If you would like to paint thickly and would still like to paint on canvas, mount the canvas or linen on masonite, and prime the canvas with PVA, glue or acrylic gesso. Then go to town and paint as thick or thin as you please! "
    So my question is, is it true that casein can be used on stretched canvas if it is painted thinly?
    I can't see why a thin layer of casein would be any less brittle than a thick layer.
  • Question asked 2016-11-30 23:18:54 ... Most recent comment 2016-11-30 23:36:00
    Drying Oils Oil Paint Pencil Pigments
    Question
    I see warnings of the possibility of graphite migrating to the surface of an oil painting over and over again.

    I have been using graphite for over 40 years without seeing any migration, and considering that graphite is used as a pigment in oil, I'm inclined to think that graphite migration is a myth.
    Is there any evidence that graphite can or does migrate through oil paint?
    Note, I'm not talking about a drawing becoming visible because the paint over it has become more transparent over time.

    Thanks.
  • Question asked 2016-11-30 16:15:33 ... Most recent comment 2016-11-30 16:47:00
    Pigments Technical Art History
    Question
    What colors did Titian use
  • Question asked 2016-11-30 05:51:35 ... Most recent comment 2016-11-30 09:12:00
    Industrial and Non-Traditional Products
    Question
    I recently watched a video, on New York Academy of Art Facebook Page. Vicent Desiderio is using flashing cement in his work. I guess the reasoning being it is made to withstand harsh weather conditions, heat and cold. This must have some pit falls, even though he produces remarkably evocative beautiful work. Can this be considered a safe material to work with? Thanks, Steven Lewis
  • Question asked 2016-11-29 15:44:53 ... Most recent comment 2016-11-29 15:58:00
    Industrial and Non-Traditional Products Other
    Question
    I am looking for a hard black wax as a surface covering on cement sculpture. Hard enough to reject fingerprints. Any suggestions would be greatly appreciated.
  • Question asked 2016-11-29 14:10:40 ... Most recent comment 2016-11-29 14:17:00
    Chalk Oil Paint Other Paint Additives Paint Mediums
    Question
    What are your thoughts regarding mixing Chalk, calcite, barite, kaolin (clay), talc, silica (quartz) and bentonite directly into the paint or into the medium while painting. I love some of the effects that are possible when you add chalk or barite into your paint on the palette, but I'm worried about permanence. I don't use any mediums except for linseed oil and or stand oil.
  • Question asked 2016-11-29 07:35:26 ... Most recent comment 2016-11-29 09:25:00
    Mural Painting Rigid Supports
    Question
    It seems that traditional marouflage adhesives were made of mixtures of animal glue and starch paste. Such adhesives are generally strong and can last for decades, but are quite reversible by mechanical means. Are there any modern products that could be equally strong and reversible for adhering painted canvas to walls or ceilings? Perhaps commercial wallpaper pastes with the addition of animal glue? Are there any tried and true adhesive recipes for this? It seems they are hard to find.
  • Question asked 2016-11-28 18:39:45 ... Most recent comment 2016-11-28 20:23:00
    Acrylic
    Question
    I have recently been creating some abstracts using acrylics. In order to create cells I have watered down the paint considerably, ( it seems to be about density) Now that I have weakened the bond I was wondering if I use the pouring medium from Liquitex on top of the finished canvas or board, would that seal the painting underneath or should I use varnish or resin? Thank you!
  • Question asked 2016-11-28 16:18:20 ... Most recent comment 2016-11-28 16:23:00
    Drying Oils Environment Oil Paint Paint Mediums Solvents and Thinners
    Question
    Has any one of you experience with Lavender spike oil or Zest-it products to replace gamsol in the beginning of the painting process? I would like to work with more environment and health friendly products. Normally I use gamsol for the transparant wash and mix gamsol and lineseed for Amber underpainting. Lineseedoil in my first layer of full paint and stand oil in second layer. Than when finished a varnish. So if I start with a spike oil (which maybe does not give a stable paint layer) from the beginning in the first 2 steps, I need varnish in my second paint layer which Is not preferable. So how do I get a wash and underpainting transparant but still working or adapting all the fat over lean steps?
  • Question asked 2016-11-25 19:04:02 ... Most recent comment 2016-11-25 22:13:00
    Question
    Is Gamblin Rich Gold oil paint okay to use in outer layers in my paintings? I paint indirectly and will use it for small areas such as on a bird’s feathers or parts of leaves, etc. I don’t know anything about these metal paints and hoping they’re durable paints. I bought it on a whim. In case this is relevant, I only use a little linseed oil as my medium. Thank you for starting this site for artists!
  • Question asked 2016-11-23 01:39:58 ... Most recent comment 2016-11-23 09:09:00
    Question
    I have an encaustic work on a stretched headed canvas  that is delaminating. It is melted crayon. Can it be warmed to readhere it?.
  • Question asked 2016-11-23 09:03:55 ... Most recent comment 2016-11-23 09:04:00
    Art Conservation Topics Encaustic
    Question
  • Question asked 2016-11-22 06:01:00 ... Most recent comment 2016-11-22 07:14:00
    Rigid Supports Sizes and Adhesives
    Question
    What is the difference between BEVA 371, Beva gel and BEVA 371 film? The film is really quite expensive so I would rather buy a gallon and just paint it on, as long as that will have the same effect of reducing bubbles.
  • Question asked 2016-11-21 13:34:07 ... Most recent comment 2016-11-21 13:35:00
    Pastel
    Question
    20 year old pastel sticks Question: I have a fantastic collection of fine pastel sticks. From Schminke to Rembrant, to Windsor Newton, etc. Perhaps 1000. I had to stop using pastel due to living in very hot climates year round and limited interior work space/health. I am now ready to take pastel painting up again, and find that many sticks are pretty chalky and or dry. Is there any safe way to revive them? Thank you very much.
  • Question asked 2016-11-21 13:25:52 ... Most recent comment 2016-11-21 13:34:00
    Pastel
    Question
    I have a fantastic collection of fine pastel sticks.  From Schminke to Rembrant, to Windsor Newton, etc.  Perhaps 1000.  I had to stop using pastel due to living in very hot climates year round and limited interior work space/health.  I am not ready to take pastel painting up again, and find that many sticks are pretty chalky and or dry.  Is there any safe way to revive them?  Thank you very much.
  • Question asked 2016-11-21 13:27:08 ... Most recent comment 2016-11-21 13:34:00
    Pastel
    Question
    Title: 20 year old pastel sticks

    Question: I have a fantastic collection of fine pastel sticks. From Schminke to Rembrant, to Windsor Newton, etc. Perhaps 1000. I had to stop using pastel due to living in very hot climates year round and limited interior work space/health. I am not ready to take pastel painting up again, and find that many sticks are pretty chalky and or dry. Is there any safe way to revive them? Thank you very much.
  • Question asked 2016-11-21 09:32:51 ... Most recent comment 2016-11-21 09:42:00
    Grounds / Priming Drying Oils
    Question
    I was at. A product information session during which the paint company representative recommended applying linseed oil to the ground, wiping off all the excess until the surface appeared dry, allowing the surface to dry 24 hours as a solution/to avoid sinking in. Is this good practice?
  • Question asked 2016-11-20 17:09:09 ... Most recent comment 2016-11-20 17:39:00
    Studio Tools and Tips
    Question
    I'm now painting in a basement studio and the light is terrible. I bought white 5500Kelvin bulbs but to my dismay they look bluish... which are your favourite brands of white light bulbs? It can be any type of light bulb, as I can fit both halogen and fluorescent. Thanks.
  • Question asked 2016-11-19 23:55:34 ... Most recent comment 2016-11-20 00:02:00
    Art Conservation Topics Other Rigid Supports
    Question
    When adhering a painting on linen to an ACM/Dibond panel using BEVA (Solution or film) using a domestic iron, is it possible to sufficiently/successfully activate the BEVA by applying the heat to the back of the aluminium panel rather than the front of the linen/painting - in other words with the linen/painting side face-down rather than up? I ask because I've only ever applied the heat to the side of the Panel with the linen, but the reverse is always warm afterwards.
  • Question asked 2016-11-18 20:24:23 ... Most recent comment 2016-11-18 21:55:00
    Varnishes
    Question
    Hi everyone, which is the glossiest varnish or finishing technique that you know of? I'd like my paintings to keep that 'wet look' but damar is still not glossy enough... ideally a varnish that won't discolour over the years. I don't mind even burnishing it if you feel that can improve gloss? Thanks.
  • Question asked 2016-11-18 10:26:24 ... Most recent comment 2016-11-18 10:36:00
    Pigments
    Question
    What are your thoughts on PW12.77990?  I saw this on Kremer's online shop.
  • Question asked 2016-11-11 12:41:52 ... Most recent comment 2016-11-17 10:28:00
    Question
    Please do not approve this question, I am using it to test a new feature.
  • Question asked 2016-08-21 10:53:21 ... Most recent comment 2016-11-16 18:37:00
    Rigid Supports
    Question
    I am interested in learning more about appropriate ways to prepare an ACM panel
  • Question asked 2016-11-16 10:59:03 ... Most recent comment 2016-11-16 12:03:00
    Acrylic Oil Paint
    Question
    I recently over painted a work that I decided needed it.  The acrylic work had an area with R & F oil stick on it.  I thought the gel medium would allow this to be fine but need to ask.The R & F was rough.
  • Question asked 2016-11-16 00:07:22 ... Most recent comment 2016-11-16 06:18:00
    Acrylic Alkyd Flexible Supports Handling and Transportation Oil Paint Paint Mediums Storage
    Question
    I have been asked to paint a backdrop for a photographer, on a large canvas (5' x 8') with the following criteria:
    - the canvas will be rolled up so it must be flexible and not crack over time.
    - the end result must be matte, not shiny.

    I'm used to painting in oil, with a strong preference for oil, but I'm thinking acrylics would be the better choice. I"m thinking acrylic paint on canvas as acrylic can be flexible and inexpensive over a large area of canvas. There would be just two colours and those pigments are very inexpensive, but can be extended with a matte medium.

    Alkyd is also flexible, am I correct; and mediums could be added to oil paint, with a little bit of wax medium to matte it out, but I'm concerned with the flexibility of the surface if I use wax medium in any capacity.

    We don't expect this to last forever, but the photographer should be able to get the most of this for a long time. So I think we'd be happy if this piece can last for at least 5 years.

    What would be recommended?
  • Question asked 2016-11-15 11:11:44 ... Most recent comment 2016-11-15 13:39:00
    Art Conservation Topics Mural Painting Oil Paint Scientific Analysis Solvents and Thinners Technical Art History Varnishes
    Question
    I was encouraged to reformulate my FB question below here by Kristin DeGhetaldi. Feel free to moderate my message to be more on point and specific. Anyway, I wondered about the practice within the restorers/conservators community worldwide  on the removal of varnish or cleaning of historical paintings? Is there a consensus to tread really carefully when handling such a task? A standard procedure in place for assessing risks of overcleaning? One would assume that to be the case but the horror stories of overcleaned/altered works of art in the (sometimes relatively recent) past are plentiful, no? Is there consensus and acceptance across the field that irreversible errors were made in the past and a determination to avoid those in the future?
  • Question asked 2016-11-13 13:35:24 ... Most recent comment 2016-11-13 15:39:00
    Acrylic Varnishes
    Question
    Would Golden GAC 400 be OK to use as a final varnish on acrylic paintings? It foams less than Golden Polymer Varnish on a fairly rough surfaced acrylic painting. I see on the Golden site they recommend GAC 100 as an isolation coat before final varnish on acrylic paintings.
  • Question asked 2016-11-13 09:01:02 ... Most recent comment 2016-11-13 09:38:00
    Art Conservation Topics Sizes and Adhesives Solvents and Thinners
    Question
    Is the solvent Napthol, 'cut' 50:50 with BEVA 371b solution to adhere linen to Aluminum Composite Material, harmful to the un-sized & un-primed side of the linen (on the reverse side of the properly-prepared canvas being attached to the ACM) onto which it is applied?
  • Question asked 2016-11-13 09:05:48 ... Most recent comment 2016-11-13 09:11:00
    Rigid Supports
    Question
    What materials & procedure constitute 'best-practice' when cradling large pieces of Aluminum Composite Material (Dibond etc)  to prevent warping? What materials should be used for the cradle itself, and for adhering the cradle to the ACM panel?
  • Question asked 2016-11-11 09:59:36 ... Most recent comment 2016-11-12 22:20:00
    Art Conservation Topics Varnishes Rigid Supports
    Question
    Please give your suggestion on how to safely remove damar varnish, light touch up,  transfer canvas to aluminum support. Oil painting, 50 x 40", 30 years old
  • Question asked 2016-11-12 21:58:07 ... Most recent comment 2016-11-12 22:06:00
    Health and Safety Pigments
    Question
    I have heard that Italy and some other EU countries are considering outlawing pure cadmium colors as too many artists are washing their brushes filled with the paint into the water system.  For this reason I have learned to clean my brushes using no water.  Have you heard this and if so would you comment.  If not would you recommend a safe way to clean brushes that is good for the environment?  Thank you.
  • Question asked 2016-11-12 18:43:55 ... Most recent comment 2016-11-12 18:48:00
    Flexible Supports Rigid Supports
    Question
    Hello. I am aware of the consensus that (oil) painting on a rigid rather than flexible support is best-practice, but I still feel confused & unsure what to choose to paint on when I want to make large paintings; say 50" x 60" or larger - Aluminum composite is both hard to come-by where I live, and at 3mm thickness, is liable to bend at the sizes I'm talking about, unless cradled... but then I have been told that cradling often creates its own problems. These same issues go for wood panels too, with the added problem of increased weight & natural warp. So, back to the question: What should painters be working-on when they want to paint on a larger scale? Thank you.
  • Question asked 2016-11-12 17:11:58 ... Most recent comment 2016-11-12 17:16:00
    Drying Oils Oil Paint Pigments
    Question
    Is zinc sulfide embrittlement comparable to that of zinc oxide? As a pigment does it pose the same risks in a paint film?
  • Question asked 2016-11-11 14:35:12 ... Most recent comment 2016-11-12 12:23:00
    Drying Oils Varnishes Oil Paint
    Question
    I would like to make some changes to an oil painting which I thought I had finished. It is touch dry. I used Old Holland oils with a small amount of linseed oil as a medium. Should I use retouch varnish on the area I wish to rework? I have been told that I can put a layer of linseed on as an alternative to retouch varnish.. Advice much needed thank you Fiona McClean
  • Question asked 2016-11-12 05:28:41 ... Most recent comment 2016-11-12 11:49:00
    Pastel Matting, Framing, and Glazing
    Question
    I would be grateful to see any information your group might have or know of, historical or current, concerning the long standing practice by some artists of framing pastel works in direct contact with the glass -  specifically concerning mold / fungus growth. 
    <p>
    Of greatest interested would be any documented instances of mold / fungus growth that were known or  suspected to have been directly caused by this practice. Also wondering if there have ever been any studies or laboratory testing done to determine the propensity for mold / fungus growth of  pastel works in general and particularly those done on any of the current day sanded papers.
    <p>
    Please note that I am not looking for information concerning the alteration or disturbance of the pastel work by the direct contact with the glass as I have been able to test this extensively myself.
  • Question asked 2016-11-10 19:00:28 ... Most recent comment 2016-11-10 21:39:00
    Encaustic Varnishes
    Question
    What archivally sound permanent or removable protective finishes if any have been used/recommended for encaustic works that provide a more durable finish on top of the wax surface to help protect it from pollutants and contact damage? Under the recommendation of Golden products I have been using their removable acrylic varnish for about a year now with excellent results but would like to look at other options.
  • Question asked 2016-11-10 18:05:59 ... Most recent comment 2016-11-10 19:10:00
    Art Conservation Topics
    Question
    I inherited an oil portrait which is starting to show some damage, cracking especially in the very dark areas of the hair where the paint is thick. There are some tiny missing chips of paint as well. What can I do to prevent further damage and protect this paint as much as possible? Thank you, Mona
  • Question asked 2016-11-10 09:43:46 ... Most recent comment 2016-11-10 11:59:00
    Art Conservation Topics Flexible Supports Sizes and Adhesives
    Question
    ristin DeGhetaldi, I am researching sizing of canvas for stretched supports. I have tried both Gamblin PVA and GAC100 for preventing the leaching of oil to the canvas, to prevent rotting. I prefer using the Gamblin PVA, because it seems to soak into the canvas better, and therefore is easier to use (also, it is less cost prohibitive). However, I am still concerned about too much flexibility with either of these PVA sizings when used with acrylic gesso and stretched canvas. The fully cured oil paint will be more rigid than its substrate, which could lead to cracking, long term. To do it better, and get more compatible flexibility, I am thinking that adding GAC 400 might be a good option. This would make the substrate stiffer and of similar rigidity to the fully cured oil paint. Am I right here?

    If so, what would be the best order of operation? I am guessing a layer of Gamblin PVA on the front then back, before stretching, then a layer of GAC 400 on the front, after stretching. Then I would wait a day before gessoing twice with high quality acrylic Gesso, like Golden. Then, I would wait 3 or 4 days before painting. I would appreciate your opinion. Thanks!
  • Question asked 2016-11-07 22:12:01 ... Most recent comment 2016-11-08 07:48:00
    Technical Art History Art Conservation Topics
    Question
    I am wondering about the reliability of the information in Ralph Mayer's book the Painters Handbook? If not reliable and even if it is I would appreciate any and all recommendations.
  • Question asked 2016-11-06 17:27:55 ... Most recent comment 2016-11-07 01:28:00
    Egg Tempera Health and Safety Pigments
    Question
    I've recently acquired some dioptase pigment which was recommended by a friend. It seems to be very transparent and is a beautiful colour, so very useful as a glaze. I'd love to know any information on colour lightfastness and stability. I'm using it in egg tempera. I believe it's pretty toxic. Thanks.
  • Question asked 2016-11-06 22:06:23 ... Most recent comment 2016-11-07 01:28:00
    Pigments Technical Art History
    Question
    In another forum, this pigment was mentioned as a suitable pigment to use instead of verdigris.  Can you please tell me more about this pigment, the historical period it was used in and its stability and light fastness in egg tempera or oil painting binders?
  • Question asked 2016-11-06 04:20:42 ... Most recent comment 2016-11-06 05:27:00
    Question
    How do I see all posts on a subject.  Just want to read, no specific question yet.
  • Question asked 2016-11-05 13:08:33 ... Most recent comment 2016-11-05 21:24:00
    Egg Tempera Paint Mediums
    Question
    I'd be very grateful for some advice about egg tempera combined with oil glazes.
    I've read Koo Schadler's article on her website but I'm still wondering:
    1. Is it absolutely necessary to isolate the egg tempera with shellac?
    2. How long would you need to leave the ET to dry?
    3. What would be the best medium to use in the oil glazes? I bought some Rublev oil paint but I can't find any oleogel here in the uk.
    (I'm an experienced egg tempera painter).
  • Question asked 2016-11-04 11:15:37 ... Most recent comment 2016-11-04 11:24:00
    Storage Studio Tools and Tips Varnishes
    Question
    Oftentimes when my paintings are drying, they collect dust, hairs and schmutz that I need to remove before varnishing. If the paint layer is cured sufficiently, I use a foam brush and lightly brush over the painting to remove it. I wonder if a tack cloth can be used, or will that leave residue on the paint surface?

    What is the recommended way of removing inevitable dust from an oil painting?
  • Question asked 2016-11-03 10:33:55 ... Most recent comment 2016-11-03 13:03:00
    Egg Tempera Pigments
    Question
    I have recently found a good source of more or less affordable azurite.  The pigment is beautiful, easy to work with in egg tempera.  Its shade is also easily controllable by grinding more (it gets paler as you grind it).  However, one issue that I found bothers me a bit.  When I finish the work, it is a beautiful tone of blue with a hint of green in it.  However, after a few months, it gradually turns more and more green.  Not entirely objectionable, and in fact the color harmonizes better overtime.  But is there a way to stop it from greening?  I read somewhere that many egg tempera works and frescoes were done in azurite but it didn't green.
  • Question asked 2016-11-03 11:02:36 ... Most recent comment 2016-11-03 13:03:00
    Dyes Gilding Varnishes
    Question
    In some Russian icons of the 18-19 cc, there was a method of "gilding" without gold leaf.  Metal leaf (often silver leaf) was used, but then coated with a yellow-tinted varnish.   It didn't look like gold but had its own distinct charm and softness.
    Recently, I tried to replicate this technique by using aluminum leaf; however, I cannot find a suitable colorant for the varnish.  Kremer Pigments suggested something (organic pigments) but these turned out to be not soluble in a solvent-based varnish.  Even though the pigments were transparent, the varnish turned cloudy, just like you'd add a mineral pigment such as yellow ocher into any liquid. 
    Is there a type of dye that one can be completely dissolved in mineral spirits (i.e., solvent-based polyurethane varnish)?
  • Question asked 2016-11-03 07:46:23 ... Most recent comment 2016-11-03 07:56:00
    Ink Other Varnishes
    Question
    I have been asked to create an art work that will be between layers of shellac, on a guitar.  The client says the last time this was done, the artist used sharpies.  I'm concerned about how that will look years from now.  It needs to be very flat, so pigment pens might be the only way.
  • Question asked 2016-11-02 14:05:28 ... Most recent comment 2016-11-02 15:26:00
    Art Conservation Topics Environment
    Question
    Asking for a friend: She had some colored lithographs stored in a flat file that had some water damage. After laying out to dry, there's been some small mold growth on the edges/border. Is there a way that I can treat the area to prevent/minimize further growth or should I store them differently? Or take them to a professional?

    - Craig Lee
  • Question asked 2016-11-02 12:53:35 ... Most recent comment 2016-11-02 13:35:00
    Acrylic Drying Oils
    Question
    Can matte acrylics can be used (ie thinned with matte medium) under an oil paint film, ie as an underpainting/ebauche layer?
  • Question asked 2016-11-01 15:34:30 ... Most recent comment 2016-11-01 20:45:00
    Question
    Under what heading would oil paint questions be under?
    Steven Lewis
  • Question asked 2016-10-29 05:26:54 ... Most recent comment 2016-11-01 14:45:00
    Varnishes
    Question
    How do I remove Damar varnish, oil panting on linen, 28 years ild
  • Question asked 2016-10-31 06:10:06 ... Most recent comment 2016-10-31 09:10:00
    Flexible Supports Gilding Other Sizes and Adhesives
    Question
    I am about to start oil painting on canvas with gilded areas (gold leaves) and would be thankful for any advice when it comes to this, especially when it comes to the longevity of the gilded areas. I had previous experience in gilding hard surfaces (traditional Byzantine orthodox icons), but never worked with gold on canvas.
    To be more precise, let's start with size/mixtion. I am using Lefranc & Bourgeois Charbonnel Mixtion (3 hours). Any thoughts on the quality of that size? Will it become hard and brittle over time and cause the gold to crack due to the canvas' flexibility? I've got advice to apply one layer of size, let it dry out and then apply second layer of it before I put on the gold leaves - is this smart thing to do? Supposedly, this should somehow increase the flexibility of the surface...
    Additionally, I know gold is chemically mostly inert material, but are there any known problems related to the chemical reactions between the gold and oil paints? Should I additionally protect the gilded surface, or the varnish that I'm using is enough (Lefranc matt picture varnish for oils/acrylic)?
    Any tips&tricks related to best practices of gilding the canvas are most welcomed. Thanks!
  • Question asked 2016-10-29 08:45:07 ... Most recent comment 2016-10-29 08:57:00
    Acrylic Art Conservation Topics Varnishes
    Question
    I have heard many variations on this and was wondering if there was any sort of agreement on the varnishing of acrylic paintings.
  • Question asked 2016-10-29 07:59:25 ... Most recent comment 2016-10-29 08:09:00
    Art Conservation Topics Drawing Materials
    Question
    Can you please tell me how to remove small spots of rust left on a drawing that was held by metal bulldog clips?  I'd like to not have to trim the paper.  If left , what would be some adverse results? Thank you.
  • Question asked 2016-10-18 21:55:31 ... Most recent comment 2016-10-20 14:12:00
    Drying Oils Other Varnishes
    Question
    There are several areas on my painting that appear matte and uneven compared to the rest of the composition. I am not quite done painting so am unsure how to proceed...
  • Question asked 2016-10-18 11:03:07 ... Most recent comment 2016-10-18 11:04:00
    Health and Safety Pigments
    Question
    I have been hearing a lot about the toxicity of lead white paint.....but some of my colleagues swear by it. I am sort of torn at the moment...

Secondary Search Results: Answers & Comments

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  • This is a Moderator Answer - Click Here to view the full thread.

    I will respond within your post for convenience. My responses will be in red.

    Thank you very much for the information. I did try an acrylic dispersion ground from liquitex, but for some reason it did not adhere that well to the canvas, the epoxy could be pulled off a bit too easily.  Could the reason be that it was applied directly to the fabric prior to sizing it with an acrylic medium? or not the right thickness and amount of layers applied? 

    This does not make sense to me. The acrylic dispersion ground should have adhered perfectly well to the canvas without a size. The size would just prevent the ground from soaking into the canvas. What kind of canvas are you using? Is this one specifically for artists or could it have some sort of commercial coating that is impeding adhesion?

    For sizing you mention that it would be a sufficient hold out , do you mean permanent ? 

    I simply meant enough of a size layer to prevent the epoxy from actually soaking into the fibers of the canvas.

    Regarding the sizing , is an acrylic polymer (acrylic dispersion medium designed as size) more durable (archival) than a PVA size ? If yes could you please recommend the most durable ones in the market ?

    I am not specifically saying that acrylic dispersions are more "archival". My understanding is that they are capable of creating a more rigid surface which may be of use to you are you are applying a brittle epoxy layer to a flexible support and any added rigidity would help to offset this to some degree.

    You recommended following directions for sizing fabric intended for an oil ground, is there a particular reason for this ?

    I only meant that if you applied it in a similar manner as one used for an oil ground, the layer would be sufficient to prevent the epoxy from soaking into the canvas fibers.

    Do you think that Size → Ground→ Epoxy is a permanent and best solution instead of Ground→Epoxy or Size→Epoxy ? 

    I think that either a canvas with a size and a ground or even a substantial acrylic dispersion ground without a size would be preferable to the size/epoxy, as they would create a more rigid fabric surface than would a canvas with only a size. My worry is that a flimsy fabric with only a size would result in the cracking of the brittle epoxy over time.

    If you think the Sizing → Ground → Epoxy is the best solution , could you recommend the best grounds + sizing for this application ? 

    We at MITRA generally do not recommend specific manufacturers unless they make unique products and any profession grade of acrylic dispersion medium and ground should suffice. However, I am aware that when used as a size Golden’s GAC 400 is specifically formulated to create a stiffer fabric, which may be helpful in your situation. Their recommendations can be found here:

    https://www.goldenpaints.com/technicalinfo_gac100s

    Thank you in advance for your help. 

    Best.

    Tao

  • This is a Moderator Answer - Click Here to view the full thread.

    I know of no such database mainly because what you propose is incredible complicated and in some ways not meaningful. When you write the refractive index (RI) of a paint sample what exactly do you mean?

    This is a great article on RI and transparency/opacity in paint:

    https://www.naturalpigments.com/art-supply-education/transparent-opaque-paints/

    RI describes the speed that light moves through a material as compared to the speed it moves through a vacuum. This becomes important when light moves from the interface of one material into another (how light bends). There are multiple RIs in a given paint. There is the RI of the oil or mixture of oils. This is easy to identify, at least initially as the RI of oxidized drying oils increase slightly over time. Each pigment has a specific RI (actually many have more than one, depending on particle shape and other factors). To this, you then add the RI of any stabilizers, like aluminum stearate, etc. The closer the RI of the various components, the more transparent they are in each other. This why lower grade cadmium paints that contain a high proportion of low RI aluminum stearate are inherently more transparent than those that contain little or none. In paint, we are interested in the effect of one or more RIs in a matrix of another. In essence, paint is a mixture of RIs, all of which would contribute to a paint of a certain transparency/opacity at a given thickness. This is not the same as a RI for a given paint.

    As to particle sizes, many pigments come in different grinds to maximize for different effects or for specific reasons (greater transparency for glazing, etc) so just knowing a pigment number would not always be enough to discern this info. Also, I would guess that manufacturers have records of the particle sizes and morphology of each pigment they use for each specific paint in an effort to maintain consistency from batch to batch, but it is certainly not common knowledge and is unlikely to be easily obtained.

    Please let me know if I somehow missed the point of your question.

  • This is a Moderator Answer - Click Here to view the full thread.

    I believe that an acrylic dispersion medium designed as a size would work perfectly well for this purpose and should remain compatible. You should follow directions for sizing fabric intended for an oil ground. This should provide sufficient hold out.

    However, I do wonder if you are purposefully avoiding applying a nacrylic dispersion ground (often called acrylic gesso) or if that is an option. First sizing with an acrylic medium and then multiple coats of such a ground would both seal, fill in the interstices, but also provide rigidity which could be very beneficial as the epoxy material you intend on using is likely to become quite brittle. It is generally best practice to apply more flexible materials over more rigid ones, rather than the other way around.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Sorry for the late response - just seeing this now. If the cotton wipes truly are just cotton, they should be fine - certainly better than newspaper. Give them a try.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​The answer would be inherently yes - just as cotton paper is better than paper made from wood pulp. But instead of cotton rags, you could use simply 100% cotton drawing / printmaking paper. If cost is an issue, perhaps a local drawinf class or printmaking studio would be a source of used paper that could be torn into strips and reused?

  • This is a Moderator Answer - Click Here to view the full thread.

    Hi -

    At least for any acrylics you should be fine as the degree of acidity is simply not that aggressive in terms of attacking or causing structural degradation of the acrylic polymers, which are physically extremely durable. The main issues are the ones you have already mentioned - the continued yellowing and embrittlement of the underlying paper. Lastly, keep in mind that while the acrylics will provide a physical barrier and coating, they are still porous and moisture can certainly travel through to the layers below. I did try to look up direct conservation literature that might address this more directly and there were some on the conservation of paper mache masks and sculptures that seemed to suggest that the painted layers were unaffected and that most issues were more structurally connected to the paper mache itself. For one example, see:

    https://journals.openedition.org/ceroart/5248

    This was particularly interesting as the paper mache was coated with a clear acrylic layer after completion and when the pH was tested it still had a neutral rating of 7.0-7.2. Of course every piece is different but it did lend some support for the durability of the acrylic when used on top of inherently acidic paper stock. One might also want to look at cases where acrylics were used in conjunction with collage materials or for that matter, even the use of acrylic gesso on top of cardboard or paperboard.

  • This is a Moderator Answer - Click Here to view the full thread.

    The issue with acidic adhesives is that they can attack the organic components used in easel painting (eg cellulose in fabric). This is not the issue in the panels you are describing, so I would not worry about the acidity.

    I would want to make sure that the existing layer would not be a source of delamination overtime. Is the adhesive is both strong enough to hold the veneer and that it has good aging properties assuring that the adhesion will last over time? The reason I say this is that even if you coat it with an acrylic dispersion, if the existing adhesive layer fails, there could be delamination at that site anyway. In a laminate structure, each layer needs to have the proper adhesive and cohesive properties. It is sort of like the weakest link in a chain analogy.

  • This is a Moderator Answer - Click Here to view the full thread.

    You are correct; we want to avoid creating the appearance of undulations associated with the bracing overtime. I have found that if you use a hardwood like poplar or oak for the crossbrace and secure it to the outside members using “L” brackets and screws, the bracing provides support without gluing it to the panel.  

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Hi there...actually if you enter "newspaper" into our search field a couple of interesting threads come up....I suggest reading this one first and let us know if you have any additional questions after doing so.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​I would also point out to the artist that oil paints differ in composition from traditional printing inks, even though they do both contain oil, often the same one.  Nonetheless, heavily sized papers are usually recommended to use as supports for oil painting and lightly sized papers for printing.  This apparent contradiction has, I believe, to do with the proportion of oil, its type, the presence of driers, the factors that Joan notes, etc, between the two media. 
    Margaret Holbein Ellis

  • This is a Moderator Answer - Click Here to view the full thread.

    ​The following is from Joan Irving, Head of Paper Conservation at Winterthur Museum: What a thoughtful question. Historically, printing papers for oil-based inks had very little to no size at all. This was particularly true for intaglio, where papers needed to be soft and pliant to conform to the cut lines of a copper plate. Printing papers remained like this, or "soft sized"  (versus "hard sized" for writing with water-based media) for eons until the emergence of lithography. With planographic printing, papers were said to be "half sized" - not as hard-sized as writing papers but more than intaglio papers and just enough sizing to tolerate the very tacky, almost adhesive-like, lithographic inks.Occasionally, with these historic prints, we can see a bit of migration of the oil binder -- either sinking into the paper or creating light brownish discoloration on the verso. This may have more to do with the quality (type of nut oil, length of cooking, etc.) and less to do with sizing.I am not familiar with modern oil-based inks but I think the longevity of the print lies in the quality of the paper fibers and how balanced (pigment to binder) the ink formulation is. My colleagues who see more contemporary art may have other impressions -- pun intended!

  • This is a Moderator Answer - Click Here to view the full thread.

    There is really no better white than lead white for oil painting. It is superior in flexibility and permanence. It is, however, less “white” than zinc and titanium and is both expensive and toxic. It is easy to use lead white safely but some would prefer to avoid both the expense and issues of toxicity disposal. So in lieu of lead white you really only have titanium white. Zinc white has been shown to be very problematic even in small proportion. Other whites lack the opacity to be used as an all-purpose white (barium sulfate, etc) Titanium dioxide on its own has issues as well. It tends to make very weak paint films. Unfortunately, for oil paint, all whites other than lead are a compromise. That is not to say that permanent paintings cannot be made using titanium white, only that it is inferior to lead white. 

    One could certainly use Gamblin’s ground, which is titanium white and calcium carbonate in an alkyd binder. It should take varnish in a similar manner as the rest of your painting and should remain white.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Richard, That sounds like a sensible approach, mixing the two blacks to arrive at something with the properties you want. Personally, I think it's best to avoid painting broad areas with lamp black alone, even on a panel, especially if you're not using a medium that can support film strength, like alkyd. Just as an example, while I don't know for certain which black was used on William Orpen's Portrait of Grace (1907), in this picture there is fairly apparent splitting of the type I think might result from broadly painted lamp black. 

  • This is a Moderator Answer - Click Here to view the full thread.

    ​I am posting on behalf of Dr. Joyce Hill Stoner:

    I believe he rarely if ever used India ink to begin a tempera – it was usually pencil – and then tempera washes and then zero in on details

    Ink was sometimes used in his water colors for very black blacks—


  • This is a Moderator Answer - Click Here to view the full thread.

    ​Amanda, I'm sure I can see some fine cracks in the sample shown in that video, and also in some product images on vendor websites.  I think it's possible the mounting adhesive and top-coating might help manage issues resulting from the cracks.  I would also want to verify the fiber content of the felt- some stone veneers use a cotton/fiberglass felt, bonded with polyester resins.

  • This is a Moderator Answer - Click Here to view the full thread.

    Ben

    While what you write is true, it would be misleading to believe that copper used as a painting substrate will not corrode in interior conditions. Every paint sample taken from an oil on copper that I have seen exhibit a blue-green layer of corrosion at the copper interface. This probably is the result of the action of the fatty acids in the oil paint and not specifically the atmosphere. Also, not all copper corrosion products are as benevolent as you suggest. Copper sulfide is relatively stable but chlorides are very problematic and are even called bronze disease. Bronze disease is a self-perpetuating problem and can completely destroy outdoor sculpture.   

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Well my first suggestion would be to take a trip to your local library to read up on the cleaning of oil paintings a bit....specifically look into "The Conservation of Easel Paintings" (eds. Joyce Hill Stoner and Rebecca Rushfield). I say you can certainly try out what you want on your own paintings to see what "works"....but keep in mind you would likely be dealing with relatively young films and obviously the appropriate cleaning solution would depend on WHAT type of oils you are using as well as the specific pigments involved....so yes, it gets complicated. But heck....that is why paintings conservators now have to go through grad school these days (AFTER taking TWO semesters of Organic Chemistry!!).

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Hi Amanda...I have reached out to Dr. Rosie Grayburn on your question as she has had a) extensive experience testing incralac and b) she knows far more about metal chemistry than many of us :) In any case it is good to hear that you have already begun sifting through some of the previous threads on issues (or non-issues) relating to copper. As to the use of incralac and the mounting system you are proposing (copper mounted to ACM) here is what Rosie had to say: 

     It’s true that like all non-noble metals copper won’t stay shiny forever. Over time, coatings become more porous allowing air/water to reach the metal and cause corrosion, but the better the coating the longer that process will take. Also, Incralac was designed for outdoor use i.e. a much harsher environment. I think Talas’ recommendation for 5-years is based on an outdoor environment. Indoors I believe it would last much, much longer (20 years+). However, If those two metals are in contact, the aluminium will corrode really fast due to sacrificial corrosion but copper will stay ‘safe’ and shiny. That would present a tricky situation...
    Dr. Rosie Grayburn
    Head Scientist
    Winterthur Museum - Scientific Research & Analytical Laboratory


  • This is a Moderator Answer - Click Here to view the full thread.

    That desk is very similar to an architects desk or drafting table. I would google some of those to see if you could not just purchase one rather than going through the trouble of building one.

    You could probably even find plans to construct one if you decided to go that route.

  • This is a Moderator Answer - Click Here to view the full thread.

    You are right that we have discussed similar issues in the past. The following thread is germane:

    https://www.artcons.udel.edu/mitra/forums/question?QID=216

    That does not cover all aspects of your question, though. If you read the above link you will see that many of the issues of covering the reverse of the canvas result from eventual embrittlement or not covering the whole of the canvas creating regions that would respond differently to environment changes and, therefore, would eventually create planar deformation. If one sized the from and back of a whole section of linen with an acrylic dispersion medium or a PVA dispersion size and then stretched it over a stretcher or rigid support (meaning that the whole of the image area had size on the front and back) I do not see why that would be a problem.

    Certainly one should not put animal glue size on both sides of the canvas. There are problems with animal glue size under a ground but it would be a real major disaster to have it on the reverse of the canvas where it has immediate access to the environment.

    However, as I wrote in that earlier thread, most of what you are trying to achieve by coating the back of the canvas could be accomplished by either stretching the canvas on a rigid support or by installing a backing board on the back of the stretcher chassis.

    It is true that we suggest stretching fabric over, or adhering to, a rigid support. This does provide many benefits (see our resources section for particulars). We also realize that the added weight, expense, and other factors will mean that some will not be interested in going that route.

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    Are you speaking about the angled desk seen on the right side of this image?

    https://www.theglobeandmail.com/arts/art-and-architecture/studio-contents-of-canadian-artist-alex-colville-to-be-put-on-display/article32172154/

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    Hi Koo

    I just returned from a conference in Belgium and finished grading so I am only now getting to your question. I will respond to each point within each section of your question and in red.

    Hi Brian,

    In a reply to a recent post you said, "…works painted over earlier compositions are much more likely to develop delamination issues over time." This raised questions for me.

    1.  Why is this so? Is it because newly formed oil paint films don't crosslink with dried paint underneath?  How much less absorbent is a dried oil paint film versus acrylic gesso ground?  And were you referring to oil paint only, or other mediums?

    It would be an oversimplification to make a definitive statement that covers all situations, but I will try to make some general statements. I do not think that it is an issue of the newer paint not “cross-linking” to the older layers but another group of possible issues. First is the diminishment of absorbency and tooth. This is inevitable. Additionally, if the underlying painting was taken to a high level of completion the artist may also be have added additional medium in their later layers exacerbating the points above. If there was a substantial period of time between the first and second composition, there could also be a certain amount of surface grime that could slightly compromise adhesion. It is also generally true that the more layers used to execute a painting, the more likely a problem can arise. Finally, there does appear to be some closing off of the surface of a painting that occurs after the paint has dried for a while. I have never seen this completely quantified but people have long spoken of the presence of an extremely thin layer of oil that sits above the surface of the pigmented layer. Perhaps due to a slight sinking of the pigments. This may contribute to a closing off of the surface. Truthfully, I have my doubts about this and its effect. I have, however, in my years conserving old paintings. I have seen many examples of paintings that were overpainted in oil by an unscrupulous restorer. Sometimes a very cautious and highly trained conservator can this cleave this overpaint cleanly off of the original paint without damage to the lower imagery. This does suggest the lack of true adhesion between the original and the later application of paint.

    I am not sure that I would make a definitive pronouncement, but generally, dried oil paint (that has not been overly thinned) would be less absorbent/toothy than a properly formulated acrylic dispersion ground. Having written that, a good lean lead white oil ground can retain a good deal of absorbency.. 

    The above is somewhat true of all mediums but there are very different degrees. It is most pronounced with oil paint. It is much less or almost inconsequential in acrylic dispersion painting where the medium is such a great adhesive. Egg tempera probably lies between but my own experience with tempera would put it closer to oil in the sense that the absorption greatly diminishes as layer upon layer of paint is added. It is very difficult to apply broad washes early on without getting overlaps while this is relatively easy after many layers of paint have been applied.

    2.  Would you say the same is true for egg tempera; that delamination is more likely to occur in works painted over earlier compositions?

    Probably, but it would depend on how many layers of tempera were used in the original composition and how dry (absorbent) or greasy (unabsorbent) the surface is. There are just too many variables to make a definitive statement.

    3. The case is often made that dispersive adhesion is primary; however in my experience with egg tempera mechanical adhesion seems equally important.  When I've continued painting on aged egg temperas (from a few weeks to over a year old; i.e. partially or fully polymerized surfaces) the paint is more difficult to work with; much more prone to lifting if I do things like sponge on watery paint, or lightly sand or polish as I develop layers.  This seems to indicate less than ideal adhesion between old and new egg tempera paint layers; and that they "are much more likely to develop delamination issues over time".  And yet I've also been told (by well-informed people) that it's fine to paint atop old, polymerized egg tempera with fresh tempera (as long as the surface is clean).   Your thoughts?  .

    You need either chemical or mechanical adhesion, preferably both. There may be a similar skin that forms on the surface of the egg tempera as it oxidizes over time. There are really a ton of oily components in egg yolk. This would be a great research project. I can’t say with authority but you, and my experience suggests that there is a diminishment of adhesion. I suspect that most of it is the loss of mechanical tooth/absorbency.

    4.  To address the less than ideal working properties of fresh tempera paint applied to a polymerized surface, I do three things to the surface: 1. Wipe off dust, 2. Do a gentle sanding with a 1500-grit sanding pad, to open the surface, 3. Apply a very thin nourishing layer of egg yolk medium (1 part yolk to maybe 8 parts water).  I'm actually not quite sure why I do #3, except that it seems to help the paint grip and behave better – but I also wonder if the nourishing layer is more detrimental (i.e. contributes toward fatty acid migration, or even delamination) than helpful.  Again, your thoughts?

    I would probably err on slightly roughing up the surface over adding egg water. The later probably does help but adding a bunch of the adhesive (binder) which by the very nature of its stickiness will adhere to the lower paint and its freshness allows adhesion to the upper layers. It does, however add a slightly slick interlayer, and more importantly, contributes a superabundance of free fatty acids, which will possibly/probably effloresce from the surface in the future. We have seen this on many 20th century egg tempera paintings.

    Brian

    Thanks as always!

    Koo 

     

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    ​Just a guess (since there's no hint of precise contents), but I assume, since the importer discloses that 'Green for Oils" is in the biosolvent category, it's likely based on methyl soyate or similar.  Look up something like Agri-pure AP-406 for more information.

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    ​Non-toxic is pretty much just a marketing term like organic. There's no real regulatory standard. It just means that there's no research to prove it's toxic. So it could be a chemical that is in fact hazardous and no one has ever done an exposure study on it. In a 5 minute search, I couldn't easily find the ingredients or safety data sheet. I'd be suspicious of any company claiming to be looking out for your health that doesn't make this information readily available. Without any information to prove otherwise it's best to assume solvents are hazardous.

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    ​These are all very interesting points and observations....first I would refer you to an earlier but related thread on the toxicity associated/not associated with spike lavender oil and other "green" solvents being marketed as safe alternatives to turpentine and mineral spirts (the latter being a rather wide and complex category). Kerith Koss Schrager's comment on the thread is particularly relevant here and I will forward your question to her in case she has anything additional to add. In the meantime some of us will try to do a bit more digging and will reach out to Sennelier to see if anyone can share some insight on these products.

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    Sorry for the late (and incomplete) reply. In my experience, there is a wide spectrum of absorbency among brands of acrylic dispersion painting ground (gesso). Some are more resistant and "fast" while others are so thirsty, the initial paint layer can look dry and waxy. I don't think I've ever used an acrylic ground that was less absorbent than a dry oil painting, though.

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    An alkyd-based gel medium may help retain ropiness better than liquid. In particular, some of the alkyd gels sold in tubes are good for retaining paint body.

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    I achieved a nice, ropy body adding 10% marbledust to titanium white tube oils, then adding a small amount of stand oil with a palette knife. The resulting mixture was long-bodied with sinuous ribbons when brushed. It's important to achieve a homogenous distribution with the marbledust first, because it's a lot harder to work the paint once stand oil has been added. I think a small pile could be mixed with a wide, flat palette knife, but a larger pile (enough to fill a tube) will require a muller to reduce clusters of powder.

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    ​Ben you are absolutely right! And I am sorry for not including this above, particularly as a Noelle is wonderful and was one of my outside readers for my dissertation and b) the book is a great resource (she also has an article in Van Eyck Studies btw). I think I tend to view her text as more of a "historiography" of how the conservation and scientific communities have viewed van Eyckian paintings....but there are certainly tidbits in there about technique.

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    It sounds as though acrylic-primed hardboard is your first choice. I can understand the storage issue with finished art, but hardboard isn't that expensive. Personally, if that were my preferred support, I would just use that.

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    A couple of questions and a comment or two.

    How textured is the impasto on the sketches. If the paint is quite thin, you have more options and the mounting would be easier. Additionally, do you paint with zinc white containing oil paint. This may have an impact on the answer as well.

    Do you intend on having these mounted on a rigid surface. If you paint thinly and avoid zinc white, this seems like overkill for a work of this size unless the mounting is to be part of the intended presentation.

    So, if the works are as small as you say, relatively thinly painted (no extreme impasto or a complete thick layer, I would think that these could be hinged, matted and framed like a traditional work on paper. The problem here is that this subject is out of my areas of expertise. If you respond affirmative to this, I will forward this exchange to one of the paper conservators and/or framing/conservation display experts among the moderators.

    Finally, while no one can stop you from painting over discarded sketches, works painted over earlier compositions are much more likely to develop delamination issues over time. Now you may think that none of these sketches is likely to be one of your masterpieces, but you never know until it is finished. I would vastly prefer that you paint your small sketches on the prepared oil-paper as you describe, rather than reusing the same substrate over and over again.  

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    I am not sure that there are any hard and fast numbers for this and it certainly does involve a number of factors. For an oil painting on linen, I would first want to make sure that I was selecting the candidates from samples that exhibit a tight weave. From this group, I would then select the heaviest weight (oz or gms per standard size, eg 15 oz per square yard) that satisfied my chosen surface texture and that I could afford for the project.

    If I had to ascribe an arbitrary number for a larger work in oil paint on a linen canvas, I would say that larger canvases (not stretched over, nor adhered to a rigid auxiliary support) should probably be no lighter than 12oz per square yard.  Again, this is an arbitrary number and does not take all factors into consideration (for instance the differences between a 3 x 3 foot painting and a six by six foot painting, the types of priming/ground, the stability of the stretcher system, the number of layers of ground, the thickness of the paint, the pigments used in the painting) You get my point.

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    ​Are you attempting to use amylase powder on one of your own paintings?

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    ​This is a question that could essentially be an entire PhD topic so I will do my best to answer. Eastlake as well as related texts (M.P. Merrifield comes to mind) from the 19th and early 20th century are certainly important documents. Not all of the technical information should be completely discounted;however, as you have already pointed out, we have now found other statements in these texts regarding materials and techniques to be inaccurate as scientific advancements have allowed to us to learn more about Flemish painting techniques. I highly recommend checking out the fairly new publication (2017) from the 2012 van Eyck Symposium entitled "Van Eyck Studies" as there are several articles within the book that provide very up-to-date information regarding van Eyck's painting techniques. There is also the articles that can be found in the National Gallery Technical Bulletin (NGTB) series HOWEVER please note that the NGTB dates as far back as 1979 and much of what is postulated early on about Flemish painting technique has since been re-visited. We now know more about pigment degradation for instance....one example would be that "copper resinate" (dissolving copper salts in a heated solution containing resin) was probably NOT used by painters (at least not frequently) until the 17th century. We are still learning more about copper green pigments. And then there is evidence that some of these painters were adding glass particles to their paints most likely to facilitate drying (additives in glass like lead for example would leach into the surrounding oil medium). Finally it seems that vitriol (zinc sulphate) may have also been used on occasion as a drier (this material was found in van Eyck's Arnolfini portrait...in addition to glass btw). 
    But as far as pigments go, that is really it as far as "new" information if you are talking about van Eyck and even Flemish painters in general. The NGTB articles are still a good go-to for that (and they are all free to download on the National Gallery London's website). I would also check out "Investigating van Eyck" and "Rogier van der Weyden in Context."
    The subject of binding medium however is a really tricky one. You will find people stating that van Eyckian painters occasionally coated certain pigments (like azurite) in protein in order to prevent them from reacting with the surrounding oil medium. You will find people stating that these painters occasionally applied lower paint layers using egg tempera, followed by oil glazes. You will find people stating that van Eyck used partially heat-bodied walnut oil in this and that color, etc. Well....all of these things have either been a) found to be incorrect or b) require careful and thoughtful re-visitation. Basically if you are trying to emulate van Eyckian works use oil. We really do not have the ability to know what type of oil or even how it was pre-treated contrary to what a small group of folks may claim. Is it possible that these artists may have also occasionally used resins as additives? Yes...of course. But again if they added small amounts of these things it is likely impossible for our current instrumentation to detect these now very degraded markers...particularly after these works have been restored 5, 6, sometimes 15 times. 

    But we do have a sense of layering...I would advise checking out our Memling reconstruction which you can find on the Kress Technical Art History website...Lower layers were generally more opaque and even a bit on the "lighter" side, with subsequent glazes applied very thinly to further refine areas of modeling.

    I hope this is somewhat helpful!

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    ​You are not unfounded in your concerns about flammability...which is why we included some information about this issue in our Health and Safety document located in the Resources section which you can find here. Give it a quick read and let us know if you have additional questions!

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    If you are looking for stability and not specific surface texture, many artists’ grade linens will suffice. I would look for a tightly woven linen of a heavy weight rather than trying to find one that has a certain number of threads per CM. The two are not synonymous. Sometimes a low thread count is the result of a loose weave and not robustness, a loose open weave creates a poor substrate if it is not completely adhered to a rigid support.

    While this is a different subject, large paintings on fabric really benefit from being stretched over a solid support, even if the fabric is not glued to the surface. Yes, this does add weight. Please read over our “Rigid Supports” documents in our Resources Section on the subject for more information.

    https://www.artcons.udel.edu/mitra/resources

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    Sorry for the belated response. This has been harder to track down than I initially thought. Few providers of artist’s canvas list the thread count. I had to go and measure some that I have in sample books and stock used for my classes. Kremer appears to offer a 8 x 10 per cm. I have a roll of hemp canvas that measured about what you are looking for (8 x 8.5) I do not have the packaging to provide the exact type with total confidence but I believe that it is SoHo Urban Artist Professional Unprimed Canvas #25 Hemp. I can’t absolutely promise that is the brand, but I think so. The fabric is very coarse with a pronounce weave and varied texture. It would only really work for large paintings and even then would likely require a number of layers of ground to surmount the rather obtrusive texture.

    There are likely other canvases that meet your criteria, it is just hard to know without personally measuring the thread count. I am sure that Utrecht had an appropriate canvas in the past but they seem to have stopped offering a range of their own unprimed linen.

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    As has been mentioned above, we are talking about sleeping in a room where pure (solvent free) drying oil paints are drying (eg linseed oil paints with no added solvent by either the manufacture or by the artist). Dispersion paints, even latex house paints offgas organic components for a while. I would want good air flow if sleeping in a tightly sealed room with large paintings covered in wet dispersion paints.

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    Cassel earth is rated 0 in terms of permanence. The tarry bituminous component never really dries and will remain sensitive to solvents. Mixed with other pigments it can result in huge open alligator cracks. Using it as a final glaze would avoid this but then you have the solvent sensitivity issue. The color of cassel earth can be easily approximated using stable pigments (it is more difficult to emulate the perfect transparence of pure bitumen but it is even more problematic than cassel earth). Why flirt with disaster?

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    Accepting the above criteria as being absolutely true, the only risk that I can even fathom is that of the spontaneous ignition of rags soaked in oxidating vegetable oils. This is easily avoided by removing any cellulosic materials contaminated with drying oils, dousing them in water, and disposing them away from your residence.

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    While I'm not a physician, personally I can't see any risk if the paintings genuinely are solvent-free, vegetable oil-based.  Does she work very large-scale or spray-apply her paint? Or, are we talking about small, typical easel paintings?

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    PV19 can be found in a range of hues from crimson to rather violet.

    Quinacridone red is the most permanent pigment in the same hue range. It is far more saturated in color and is not as transparent nor as deep in value as carmine. I would experiment with using quinacridone red and adding very small amounts of a dark burnt umber and even an extremely tiny bit of a very dark transparent color like pthalo green to deepen the value and slightly cut saturation. Now when I write extremely tiny, I am almost talking on the “homeopathic” scale ;)

    There are a few art material suppliers who offer a wide range other quinacridones and some might be closer to carmine in hue, saturation, and value. Additionally, while I have not tested it, a mixture of quinacridone red and quinacridone Burnt Scarlet PR 206 would seem promising.

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    Acrylic dispersion mediums are fine mordants/adhesives for metal leaf. I have much more concern about the imitation gold leaf. These readily oxidize even under solvent bourn varnishes. They are really not stable in terms of color and they easily tarnish. If you really need to use these copper containing metal leaves, I suggest covering them with a MSA varnish rather than acrylic dispersion mediums alone. Dispersions generally create a film that is less continuous than solvent bourn acrylics and are less able to postpone tarnishing. Also, as Matthew mentions, the aqueous system and resultant pH of dispersions can patinate rather quickly.

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    Some acrylic mediums can induce tarnishing with imitation leaf, resulting in a blue-green patina. The tarnish is not altogether unappealing, but may not be the desired effect.

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    ​Hi -

    Just to be clear about one fundamental point, while it is true that we are big advocates of nonremovable isolation coats prior to varnishing, especially to address the concerns of  future conservators about their ability to remove a varnish from an acrylic painting without damaging the paint layers, they are not strictly speaking required. In fact most artists we know or work with tend to skip them and varnish their work directly. The reasoning here is that the isolation coat is non-removable and if anything goes wrong - from a fly falling into the material, to brush strokes or foam appearing -  there is no way to remove or repair those. So prior to ever applying an isolation coat onto any artwork of value, we would strongly recommend practicing on either test panels or older paintings to gain a high degree of confidence.

    In terms of spraying on an isolation coat, you could try using something simple, like a Preval Sprayer, which we have in the States and is very inexpensive. It is often sold in auto part stores as it is used for touch ups in auto painting, but we see them also in the large stores catering to house paints. While the atomization is not perfect, and you will want to again practice to make sure you are getting results you like, it is a very low entry point for spray applications. If going this route, try out sprayable isolation coat recipe of 2 parts GAC 500 to 1 part High Flow Medium (earlier names Airbrush Transparent Extender). 

    Beyond that, Brian's thoughts on using B72 would be a viable route and worth looking into. No other sprayable options comes to mind, so would encourage you to look at a Preval-type sprayer, make the investment in an airbrush or spray-gun (especially if varnishing on a regular basis, these provide maximum control), or finally even look at skipping the isolation coat altogether and varnish directly. On this later, just realize  this will complicate any repair or cleaning by future conservators, so make note of what you have done on the back, regardless of the options you use.

    On the use of fixatives, we do not feel they would be useful as an isolation coat or interleafing layer in an artwork. They are, first of all, designed to lay down a very weak and usually non-continuous layer that works to just barely bind loose particles to paper without encasing them in a resin layer. That is just a very different function that creating a true layer that can act as a barrier for a varnish, or prior to other layers in a painting  It can also be hard to find out what is specifically in a fixative, which can complicate knowing if the material is fully compatible with everything you want to do. As for OPEN, we would recommend using a light touch and brushing on a layer of GAC 500 if wanting to continue with other layers without disturbing what you have. You can read that recommendation here:

    https://www.goldenpaints.com/technicalinfo_open#rewetting

    But as we state, doing this will also slow down the curing process and lengthen the time when all the layers have fully coalesced. If you are consistently getting more open time than you need, think about blending the OPEN acrylics with a faster drying regular acrylic paint of medium to get working properties that match your needs.

    Hope that helps!

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    ​The only examples of it being used that have survived well, from what I know, are in illuminated manuscripts. But then, those were either in closed books, or rolled up scrolls, and so not exposed to light except for the brief moments of being viewed.

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    Do you mean a fabric with 8 threads per centimeter in both the warp and weft directions (a coarse weave) or do you mean a fabric that can be ordered in 8 x 8 foot sections? I am assuming the former, and will take a look at my collection of supplier's samplebooks when I return to my office on Monday

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    No, not really. The coloring component, carminic acid, is very fugitive. In reality, it should never be used for artwork or any purpose that requires a color to last. It is best reserved for high-end makeup and Starbuck’s drinks where there is no expectation of color permanence. The use of this color is the reason why the female subjects are all ghostly white in paintings by Sir Joshua Reynolds. The red compoent of the skin color faded even in the artist’s lifetime and he lamented his use of the pigment later in life.

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    I am hoping that others would weigh in on this as well. I think that you would want to give the painting a few applications of the B-72 (allowing it to dry between coats) to build up the surface to that of a varnish and not just a super thin, fixative layer.

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    I should add a bit explaining my rationale of using an acrylic resin as an isolating layer under another acrylic varnish. The B-72 is only soluble in quite polar solvents like acetone/ethanol and highly aromatic mixtures. You should be able to remove an MSA varnish from a coating of B-72 using low aromatic mineral spirits. As usual all information about your layering should be recorded somewhere on the painting so that future conservators immediately know what materials were used on the artwork.

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    There are a couple of schools of thought on varnishing acrylic paintings. Until I read some compelling research to the contrary, I subscribe to the two-varnish system where a sacrificial layer of water borne acrylic dispersion medium is applied and allowed to dry before adding a solvent borne picture varnish. Golden Artist colors has described this well. You can read about this here.   

    https://www.goldenpaints.com/technicalinfo_varnapp1

    If spraying is necessary and you do not want to purchase an airbrush, sprayer unit, or even a cheap compressed air can system, I would think that it would be reasonable to spray the painting with a coat of  B-72 as an isolation layer before spraying it with an appropriate picture varnish.

    The availability of B-72 in a spray can is discussed on this thread about sizes.

    https://www.artcons.udel.edu/mitra/forums/question?QID=200

    Having written the above, acrylic dispersion paints are not my specialty. We have other moderators here who are far more knowledgeable about this subject. I will defer to their opinions if they differ from what I just wrote.

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    ​Sorry for have taken a bit long to respond but these questions are rather complicated...1) Question regrading the inks: To be honest, I don’t have an answer for this because I do not believe the solvent-based inkjet systems have been well studied when used as an art material. The big advantage of solvent inkjet is that it is resistant to water if printed on the correct substrate, which makes it ideal for outdoor signage (its intended purpose). The colorants should also be somewhat durable as they are often exposed directly to sunlight and pollutants outdoors. On the other hand, how people define durable is variable. Often outdoor signs are meant for shorter periods (6 months- 3 years), while museums probably want things that last longer than that (which they would get by exhibiting at a much lower light level). UV glass would help both with UV and expose to the air.2) Question regarding printable substrates: This question is difficult because parts makes no sense and parts are just incorrect. There is no such things as “polyester (acetate) films”. Polyester and acetate are two very distinct materials with one being made from petroleum and the other from plants. Acetate can’t be acid free because it contains acetic acid (which is why it is called acetate film). Also, I don’t think there is mixed data in the archival properties of acetate. It’s not stable over time. The only way to make it last is to store it in cold or frozen conditions. Whether a protective spray can help the lithograph is dependent on the surface quality of the paper and the bond between the ink and the paper surface. Not all lithographs will behave the same way.

    Hopefully this is somewhat helpful.
    Daniel M. Burge
    Senior Research Scientist/IPI

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    It is generally preferable to continue on the same thread. I am assuming that you sre contiuing from a previous thread which cn be found here. I hope the info is of help.

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    1/4" plywood seems pretty thin for a panel of those dimensions. I understand there is a big advantage in lighter weight compared to fiberboard, but I would be concerned that the cross braces might be visible through the front of the panel. If you are limiting options to common construction panel materials, have you considered thicker MDO plywood instead?​

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    ​This is possibly where you have reached the "limitations" of some of our MITRA Board experts....but I will be happy to reach out to others in the field who are specifically knowledgable about this topic. The archivability of dye/ink-jet prints is a huge topic that has of course received increased attention from the conservation community over the past decade so the information is now quite vast and overwhelming. IN GENERAL pigment-based inks are considered to be more permanent than dye-based inks. but obviously the diluent (water vs. solvent) might play a role in addition to the substrate (uncoated paper, coated paper, metal, polyester, etc.). The NEDCC has a fairly decent outline of some of these issues here but I am not certain you find the answer to your question. Again I will see if I can reach out to some of my colleagues who know more than I.

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    ​It is too difficult to give an average as there are MANY thread counts listed on the table on page 157 of the Sargent book but it ranges anywhere from 15 x 9 threads per square cm to 36 x 34.

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    I require clarification about your question, “Does that knowledge enter the realm of conservation needs?” Do you mean, does it enter into concerns about the conservation of Sargent works, or the general role of canvas and the aesthetics of appearance, etc., or something else? I am sure that you are aware; this can be a huge subject.

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    The truth of the matter is that essentially all of the linen weaves available to 19th century painters can be purchased today. What are you looking for? I recently assembled a group of historically representative fabric weaves, and with some work, I was able to fill all of the categories.   

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    ​There is an amazing publication that recently came out on Sargent which I highly recommend (John Singer Sargent's 'Triumph of Religion' at the Boston Public Library: Creation and Restoration). There are chapters that provide specific information relating to his materials and techniques, including his canvases....according to page 53 he chose plain-weave linen canvases of medium-coarse weight although others in the series are slightly finer. There is a table that has an exhaustive list of thread counts....so this book is probably right up your alley.

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    This page may give you some insight into what Sargent used for some of his paintings: https://www.npg.org.uk/research/programmes/artists-their-materials-and-suppliers/john-singer-sargents-suppliers-of-artists-materials

    I found another reference to linen used for a Sargent portrait, which was described as 23 threads per inch both warp and weft​, and it looked like a plain-weave fabric very much like modern linen: http://www.baumanconservation.com/WHZSargentExamination.html

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    ​Hi -

    We got samples of the pigment a long while ago, when it was first reported. You can see examples of drawdowns comparing it to a couple of Cobalt Blues as well as Ultramaribe Blue in our article in our Just Paint newsletter:

    http://www.justpaint.org/yinmn-blue/

    And the price so far is still anticipated to be around $500 a lb, so the paint itself will be extrodinarily expensive, although final pricing has not been released and hopefully there might be some adjustment downward. Anyway, we do understand there is always an inetrest in anything new and so plan to make it available on a custom basis once it is released for sale in artist materials. Currently it is still under review by the regualtory bodies and not available except for industrial applications.

    In the end its color space can probably be approximated with a blend of other less expensive pigments, so it might not offer enough attraction to warrant the expense.

    Hope that helps!

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    ​Hmmm sorry no....perhaps a couple of us have so I will put some feelers out just to be sure. You probably already know about this link here but we will also ask our rep from Gamblin to weigh in. I suspect that it probably will not create a hue that is completely "new" but its handling and/or aging properties might be very desirable. So stay tuned....

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    There's plenty of other companies which sell Polyester inkjet-printable films, I would suggest you look into these:

    https://www.tekra.com/products/brands/dupont-teijin-films/melinex (this item is specifically used by architects and drafters, and is polyester-based!)

    Printable Mylar:

    http://www.paperrolls-n-more.com/24-x-125-4-mil-Inkjet-Double-Matte-Mylar-Film-1-Roll.aspx?feed=Froogle&gclid=Cj0KCQjw_ODWBRCTARIsAE2_EvXrWThCd3uLTDkUpmkF6s1suy4zPCBWPoDiWnmtfgcI6nfmyo4gPioaAgPzEALw_wcB

    Alex Nichols

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    ​​Apologies for the delay....we have a few feelers out to try and address your question but if the manufacturer is actually ADMITTING that something is not archival well then I would most definitely believe them. And this leads me to believe that the coated side being in direct contact with the litho might be the least of your problems. I would actually worry more about WHY this coating is non-archival...does it turn yellow fairly readily? Will the inks readily fade after being printed onto the surface (I realize that the durability of inks is probably another question entirely)? Will the coating off-gass over time? These are all questions that I would worry about...

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    ​You are not the first to ask this question on MITRA. If you enter "BEVA" into the search field you will pull up a few threads that you might find interesting including these two:https://www.artcons.udel.edu/mitra/forums/question?QID=95

    https://www.artcons.udel.edu/mitra/forums/question?QID=266

    Also we have some information on how to work with BEVA and rigid supports in our "Rigid Supports" document in the resources section...however in general we do not recommend attempting this for various reasons outlined in the previous threads. Please let us know if you have additional questions on this topic.

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    Glad to be here, Brian!​

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    If I understand the situation correctly, I would recommend the double hardboard over the canvas. There are just too many different materials in the first scenario and each would react in a different manner to changes in the environment. The glued fabric would react very different from unglued areas; the fabric would react differently than the hardboard, etc. It could probably be done, but the situation is not ideal.

    I wonder if there is a lighter substrate that would work as well for your needs but without the extreme weight. ACM would be difficult to cut but would be structurally sound.

    Others likely have other ideas that I have not thought of.

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    It is fine to continue working on a painting when it remains wet to the touch. Problems arise when painting fresh paint over a layer that has only had the time to skin over but it remains wet under the surface. This situation is exacerbated if you apply paint containing driers over layers that have not have the time to oxidize through the whole layer.

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    ​Thanks for all of your work on MITRA Matthew.

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    Koo

    Sorry for the belated response. Kristin and I took an internet break and left town to celebrate our daughter’s first birthday over the weekend.

    A few thoughts about you earlier post. First, it is preferable to avoid hanging paintings on the interior side of an exterior wall. This is a situation where there the front and back of the panel will always see a very different moisture environment.   If it is necessary to hang a work like this, it is really essential to make sure that the panel is very well sealed and not worry if it is more so than the front.

    When I wrote that, “it is best to treat the front and back of a painting in a similar manner”, that was an ideal that is difficult to achieve in practice. I would always ere by making the reverse as well isolated from moisture suffusion as possible on a panel painting. The situation is compounded with natural wood substrates. Even ignoring the cut of the wood, the side of the panel that is more absorbent or that receives a higher RH will swell more than the other. This can collapse the wood cells on the other side creating a permanent warp. It is always safer for paint for the warp be convex rather than concave in terms of the painted side (this is also why if one needs to roll a painting on canvas, it should only be done with paint side out. Compression is far more damaging than stretching). In this scenario, unrolling the paint side out relieves pressure while unrolling a painting rolled paint side in causes additional stress. A similar situation exists for painting on natural wooden panels, just to a lesser degree.

    This rather answers your last post as well. In practice, it is probably best to fully seal the back of your panels irrespective of whether they are varnished or not. It is both difficult to replicate the layering on the front and it is always possible that varnish could be applied to the surface in the future (although a conservator should always follow the direction of the original artist in terms of whether a work is varnished during a conservation treatment.

    I hope that is more clear.

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    It is generally best to wait until initial layers a dry to the touch before continuing painting in oils and alkyds as the upper layer can slow down the oxidation of the lower layer. This can create a situation where upper layers are more brittle than those below them resulting in cracking. We see this phenomenon on many 18th-20th century paintings. The situation is exacerbated when driers are used in final layers.

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    The original Turpenoid (in the blue can) is a refined Stoddard solvent/low-odor mineral spirits. it should be used in a well ventilated area, away from sources of combustion. It can be used for thinning oil paints and some varnishes (not for Damar, Mastic or other resins normally prepared in turpentine). Turpenoid can also be used as a brush rinse. Like other OMS products, Turpenoid doesn't support drying as well as fresh, pure gum spirits of turpentine.

    "Turpenoid Natural" is a citrus-derived product that can be used to rinse brushes, but should not be used to thin oils. (The manufacturer recommends no greater than 25% Turpenoid Natural by volume in the paint mixture, but in my opinion, it really doesn't impart any beneficial properties, and can interfere with drying.)

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    I would advise against bonding mylar to a litho, since it can not be called “reversible” in any sense of the word, but if it has to be done, I would experiment with Lascaux, 360 or 498, applied to the mylar, dried for two weeks and washed to ensure surfactant removal and then run the mylar and print through a pressure roller, or cold vacuum press. When Gemini G.E.L. added mylar to the back of Lichtenstein’s wall paper print, they used Solmatol, an industrial adhesive, which had not been vetted for preservation, but it was on the verso, where it would not see the light, so it mattered less. Putting the mylar on the front brings up interactions between adhesive and image and discoloration of the adhesive, which adds up to please don’t try this.
    Hugh Phibbs

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    The back of panels is the only place that I really recommend using shellac on paintings. A good quality alkyd housepaint (I would go with at least semigloss to ensure that the paint is not too leanly bound nor contain matting agents that would create a porous film). Alkyd would likely be as good as or better than Shellac. This is one of the instances where oil or solvent-based materials win out over water borne media. A film made from a dispersion or emulsion will always be more porous or permeable than a solvent borne resin or well bound oil film. Acrylic dispersion are vastly preferable in some situations, this is just not one of them.  

    Having written all of the above, we should keep in mind that the goal of coating the back of a panel is to create a situation where the front and back of the work respond in a similar manner to changes in relative humidity. Problems evolve when the surface of a work is impervious to moisture while the reverse is effected in an unrestrained manner. A work in acrylic dispersion paints on a panel (executed in 6 layers on 3 coats of an acrylic dispersion ground, for instance) would be perfectly protected by a similar stratigraphy on the reverse. If the surface is in oil or if the acrylic dispersion painting is coated with a solvent borne varnish, it is probably best to use a solvent borne sealant on the reverse.

    As always, other moderators may have a different take on this.

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    Pressure sensitive tapes are near impossible to assess, since they are so often based on trade secrets, rather than patents. All are likely to contain plasticizers, tackifiers, and other additives that will contaminate that to which they are applied, on contact. 800 series 3M tapes, like 850, 888, and 889 are designed to be less problematic and are sold with the terms “preservation” or “conservation” appended to them, but their chemistry will always be open to a question, until the manufacturer specifies exactly is in them. One can make a tape, by applying Lascaux 360 or 498 to a strong carrier like paper ironed on to a heat sealing foil laminate (Marvelseal 360, 3 mil reflective mylar, white) and allowing it to dry, age, for two weeks and then wash off the surfactant that has migrated to the surface, with water. This material can then be cut into strips and used to mask paint areas, with minimal fear of contamination, since the Lascaux products do not have additives and owe their working properties to their co-polymer design.​

    Hugh Phibbs

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    ​Hi there.  Masking tape is generally a rubber-based adhesive with a crepe paper carrier; the ingredients are often proprietary, depending upon the manufacturer, but usually includes an elastomer (natural or synthetic rubber), a tackifier (makes it sticky), a plasticizer (makes it flexible), and often unidentified fillers.  Typically, as masking tape ages it becomes harder to remove, and masking tape left on art will almost always cause some sort of staining and degradation over time.  So, to answer your question, the amount of risk to the paper in terms of staining depends on how long you leave the masking tape on, as well as other factors such as heat or humidity in the environment - but even if you have the masking tape on the support for a very short time, you risk skinning/tearing the paper during removal and/or leaving a tacky residue.  For that reason, I'm not a fan of using masking tape on a paper support in any capacity.  That comes from my experience trying to remove masking tape which has become highly oxidized - not an easy task.

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    ​There was a similar query posted not too long ago about the durability of "acetate" films on the market, and Grafix was specifically mentioned. We would not advise using most acetate-based products for many of the reasons stated in that thread: https://www.artcons.udel.edu/mitra/forums/question?QID=420
    Certainly polyester films would be a better option here whether you plan to make a collage or not....as to the framing question it is of course always better to place any artwork that contains paper-based supports and/or sensitive media such as inks behind UV-protective glazing.

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    We try to refrain from recommending specific brands here, but in terms of weight, I would not use anything much lighter than 10 oz for a stretched canvas of those dimensions. For fabric-covered panels, many artists favor lighter weights, which are less prone to curl a panel from shrinkage. ​

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    While I wouldn't present it as definitively the "best practice", personally I get best results when stretching fabric on the bias (diagonally against the weave), especially when using a fabric that might pucker at the tacks/staples. Also, there is at least one linen (Utrecht 79D) that does not give good results when sized with RSG, so make sure to check the package label for indications.​

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    ​There is really nothing wrong with what you are proposing (stretching over already stretched/primed cotton canvas) so long as you do not over soak the linen so that the two might stick together unevenly. Just be sure you read up a bit on the pros and cons of sizing with RSG in our resources section. But all in all we feel that you are alright with going forward with what you proposed.

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    ​Cristian.

    I have slightly amended my post as a few of my stements were not well worded and even contained a factual error. None of this changes my overal suggestions to you but it is improtant to make sure that MITRA uses the most up-to-date information.

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    Thanks, Brian- that makes sense. It's gratifying to have this cleared up!​

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    A half glue/oil ground has the same issues associated with the use of animal glue (hygroscopic, very reactive to changes in relative humidity, etc). Other than this, a properly emulsified half glue/oil ground is reasonably permanent. These grounds are more flexible than straight chalk-glue and true gesso grounds. They are more brittle than oil and acrylic dispersion grounds and are best reserved for rigid supports.   

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    ​Hi Matthew

    There is a certain amount of logic to the concept. The high alkalinity would certainly saponify and/or disrupt the oily residue at the surface. It would also likely destroy the uppermost oil matrix making it overly friable and desiccated. In practice, the results would probably vary from perfectly fine to complete interlayer delamination. This is not a practice that I would condone.  

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    ​It might (?) help if you described your painting technique a bit more...do you work with thick, pastose paint? Do you apply a series of thin glazes? Matthew's recommendation seems fine to me (as I personally have little to no experience with synthetic hair brushes) but perhaps we can put some queries out if you can elaborate a bit more on your technique.

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    Brian, Some time ago, one of the paint chemists working for Utrecht suggested a remedy for beading and resistance on oil-primed canvas: wiping with household ammonia to remove oil glaze from the surface. Does this make sense​ at all? Would it be of use when resuming work on an older painting?

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    Hi Cristian

    I am glad that you took the time to post here.

    It is true that many advise against applying paint to works that have dried for an extended period of time. I have never read of any scientific study that fully explains and proves this contention, but it does seem to have some validity based on empirical evidence. Additionally, as a painting conservator who has conserved many works that were overpainted in oil paint, it is common to find poor adhesion between the original paint and the much later overpaint. The reasons for this are likely quite complex including surface grime and old oxidized varnish residue between the two campaigns of paint.

    The second issue here is the concept of overpainting an alkyd work with oil paint. In general, it is preferable to use faster drying paints in lower layers and slower drying in upper layers. The length of time that your painting has dried sort of negates that from being an issue here even though alkyds do indeed dry quicker than most brands of oil paint. More salient is the preference to use paints that are more rigid in the lower layers and more flexible paints in the upper layers. It is also important that the painting’s surface is not so glossy and closed off as to make it difficult for any subsequent layers to adhere adequately.  Recent research seems to indicate that alkyds are more brittle than oil paint. However, most of those made for artist’s use in the past had much lower pigment load than similar oil paints and result in a rather glossy surface and may effect adhesion. You are also saying that you used titanium white for the initial layers, which creates a rather brittle paint so the situation here is very complicated, and there is no way to state definitively that a specific formula will produce the desired results. Your use of additional oil and varnish probably further complicates this. To have a hope for success, you will likely have to “finish” this work with relatively few additional layers and all subsequent oil paint layers should have a bit of additional oil added to conform to the flexibility principle.  You may end up with a perfectly stable work. However, it is certainly possible that you efforts could be in vain. If your initial composition was painted using rather fat layers or with substantial amounts of additional medium, you are probably much better off just starting the composition anew.

    As a general rule, though, I am not saying that one cannot return to a painting years later as long as a number of criteria are observed. First, the original painting should not have layers of fatty glazes or medium rich applications, which would cause mechanical adhesion issues. Secondly, one should abrade the surface in some manner to create a mechanical tooth to which the subsequent oil paint layers can adequately adhere. I do not mean sanding away the painting, but using an abrasive (eg 320 sandpaper) to remove any skin of drying oil from the surface before resuming painting. I would then wipe the surface with an aromatic containing mineral spirits or even true turpentine to degrease the surface. Finally, and only if you are going to repaint the whole surface, I would probably oil out to promote adhesion with the subsequent layers. PLEASE READ OUR PDF ON THE USE OF OILING OUT, IN OUR RESOURSES SECTION, BEFORE PERFORMING THIS STEP.

    I am sure that others will have a different take on this subject but that is mine.

    Brian  

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    ​I'm sure our conservation experts will give a more complete answer than this, but in my opinion (as a painter) the proposed approach sounds like a fairly complicated combination of materials, even more so if a transitional layer of varnish or oil is applied first. If you are determined to use this panel (instead of transferring the image to a new one), I would make sure the existing paint surface is clean, and just have at it. Any time issues with adhesion or cracking may be a factor, it's advisable to paint thinly and avoid broad, continuous impasto, because some areas may perform better than others.

    One more thought: If you are just interested in the essential shapes and colors in the unfinished work, would it be out of the question to sand down some of the original paint to improve adhesion? (With personal protective gear and appropriate cleanup, obviously)

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    Without recommending a specific product, personally I've found some synthetic mongoose oil brushes to be very nice. ​The ones I've tried have offered some of the nice qualities of natural hair with good solvent resistance and nice spring even when heavily loaded.

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    There is an excellent response regarding alkyds, flexibility, drying rates and "fat over lean" in this thread: https://www.artcons.udel.edu/mitra/forums/question?QID=214

    If you feel this doesn't completely satisfy your request, feel free to post followup questions.

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    If by rubbing alcohol, you are referring to isopropyl alcohol (aka isopropanol), there are no objections to using it to clean your palette. I would opt for the higher percentage (often around 92% in water) It may even be more effective at cleaning because it does not really dilute the oil paint in the same way that OMS does. It just rather attacks it making it easier to clean up. Just make sure that it has visible evaporated before putting more oil paint on the palette and there will be no residual issues.

    Baby wipes may have other additives to make the active ingredient less drying to the infant's skin. It would likely be best to avoid them.

    Do not attempt to dilute oil paint with alcohols. They are not appropriate for thinning oils and will likely just make them separate in an unsightly manner.

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    Yes, they were Yarka. The linen actually had visible bits of tow- literally sacking/sack cloth. It was also weird (I thought) that the fish glue sizing was even used in combination with a synthetic dispersion priming. The stretchers were very solid with mortised cross braces.​ They should have just sold the stretchers!

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    I agree with the above. BTW, Matthew, were those Yarka canvases? I remember buying some when I was at The School of the Art Institute of Chicago in the mid- 90s (at Pearl Paint I think). I remember that the canvases were like burlap but that this was stretched on really heavy stretchers.

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    The canvas manufacturers I am familiar with stopped using protein sizings with oil-primed canvas decades ago, replacing them with PVA and acrylic-based products. My most recent correspondence from Claessens lists PVA since the 1980s, before which RSG was the sizing.

    The last brand I encountered that still used an animal-derived sizing was from Russia (about 20 years ago), sized with isinglass (fish gelatin). The Russian canvases were not coated on the bolt like modern fabric, but were sized after stretching (a necessity with these 'sack cloth' linens, which were so porous the sizing had to fill enormous gaps in the weave). I recall the stretchers were amazing, however, and I bought some on clearance just for the frames.

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    It seems to me that, for your requirements, and that you are going to work on panel anyway, you would be better served by simply underpainting in acrylic dispersion paints well diluted in water with no added medium, and overpainting in oil. The panel would elevate any potential issues of the flexibility of acrylic underlayers (probably way overblown anyway).

    I can see no advantage, given your rather simple needs for this layer, to introduce a complicated, potentially problematic paint layer to what could be deleterious to the longevity of the work. If you were seeking a difficult to achieve paint effect the answer may be different…but probably not. In general, it is better to keep things as simple as possible and yet still achieve the visual effects your artistic vision requires. It is ok to deviate from best practices to create a necessary effect, it is foolish to do so to achieve an easy to accomplish one.

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    Hi Jenny

    I am glad that you posted.

    What I mean by “not a natural emulsifier” is that, on its own, gum Arabic has no real emulsification properties (ie nothing that forms an intermediary between the aqueous and oily components). Before panicking, realize that the same thing is true of animal glue and other materials that have been used in emulsions; it is just that these are not stable emulsions in their raw state. If left in the jars such an “emulsion” would separate into its aqueous and oily components whereas one composed of egg and oil, or resin would stay emulsified until it began to decay.  A couple of things to remember about gum Arabic is that it will eternally remain water soluble/sensitive if used in any amount beyond the minutest proportion. Additionally, it is extremely brittle as compared to more common oil painting additives.  If you decide to use it in your works, please record this on the back of your painting.  

    None of this speaks to their applicability as an additive to tubed oil paint. What are you trying to achieve? Is there a particular effect that you hope that said emulsion would help to realize? Please look as a recent post about casein additives to oil paint. Partially mixed additives like these can easily create heterogeneous, multilayer films that are prone to cracking and delamination.  Even if the paint is completely mixed and an emulsion is achieved (very unlikely), the resulting film is going to be much more brittle than a standard oil film with accepted additives and mediums. It is also true that there are effects that can be achieved using an emulsion such as this into an oil glaze or paint layer that are difficult to replicate using more orthodox methods. One needs to experiment and decide whether such effects are required to fulfill one’s vison or if the desired quality could be achieved using more stable methods.

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    This is still a bit overly simplistic, as we do not know the acid value of the theoretical alkali refined oil in this theoretical instance. I am not sure that the differences would be marked either way, but sure, for lead white, feel free to buy it in CPL Oil. It may yellow a bit more that the alternative but it will definitely take up as much pigment as possible. Unlike many other issues on this forum, you are not going to cause any problems by doing so.

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    I am afraid that rather than having the benefits of both mediums, mixtures like this generally end up having the deficits of both and lack the virtues of either. Certainly very small amount of oil can be, and are, added to casein emulsions. A representative from Richeson mentioned that they add small amounts of oil to their Shiva Casein paints during our materials session at CAA this February. This is probably only added as a plasticizer and for tube stability. Casein is a very brittle binder and a tiny amount would probably lessen this to a small extent. I would still not recommend painting casein paints on canvas.

    There are technical reasons not to add oil in substantial amounts to casein. Casein containing large amounts of oil are known to yellow strongly. Mayer strongly cautions against this. It is certainly true that mixing oil paint with casein paint is not really creating an emulsion unless the two were vigorously mixed and mulled and even then a proper emulsion is probably not created. You would likely create a paint that had swirls of very brittle casein between or surrounding bands of very flexible (at least initially) oil paint. That is a perfect recipe for cracking and paint delamination. Additionally, it is really not technically possible to create a paint that really straddles the emulsion inversion point and allows for alternating between water and organic solvents. These mixtures are physically far more complicated than this. This subject was brought up many times by scientists at the recent tempera conference hosted by the Dorner Institute in Munich.

    Coincidentally, the mixtures that you mention actually remind me of the “mixed technique” popularized by Max Doerner where egg tempera/oil/resin emulsions were painted into oil glazes. These were very successful at creating effects that were hard to accomplish by other means but unfortunately resulted in paintings that were prone to cracking and delamination, excessive yellowing, and solvent solubility.

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    The safest plastic sheet is PET, mylar. This material has stood the test of time and makes chemical sense. Acetate, as we can see from its name, is modified with acetic acid, which makes it less stable and less chemically safe. To create the kind of sandwich you outline, it makes sense to find a polyester sheet that works with your printer and work on a method of securing it to the litho, without using any adhesive, since all of them will entail problems.  No spray will protect safely, since all are aerosols with solvent, which means that they will sputter onto the surface and are likely to have residual solvent, so please avoid that option. ​
    Hugh Phibbs

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    I think you might be confused about polyester and acetate - these are two different plastics (aka polyester most certainly does not mean acetate). I googled the Grafix film and it is made from cellulose acetate, which is laughably unstable. Cellulose acetate degrades easily, releasing acetic acid. The substrate itself yellows, shrinks, and cracks (see http://www.materialspathology.com/images/materiales/visu1g-10.jpg for an example). This process you probably have heard of as vinegar syndrome, and is a huge concern for the motion picture film industry. 

    https://www.imagepermanenceinstitute.org/resources/newsletter-archive/v12/vinegar-syndrome 

    Fun fact, the conservators who created A-D strips, which are indicator strips used to identify the degradation of acetate film, are the only conservators to ever win an Oscar!  

    https://www.imagepermanenceinstitute.org/resources/newsletter-archive/v12/academy-award

    Polyester on the other hand, is a pretty good material for longevity. There's plenty of inkjet-printable Mylar sheets on the market, as well as large rolls intended for larger printers (not just A4). 

    I would also point out that applying a fixative is generally considered a bad idea - these typically yellow and cause their own issues (the coating may contract faster than the substrate and cause physical stress). It's also probably not necessary - if something is printed on plastic intended for such a process then it should not have issues that would require fixing.  
    Alex Nichols

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    ​No one but a trained paper conservator should attempt to reduce creases in works of art. That said, if the questioner is an artist, working on material of their creation, micro manipulation of the paper fibers might be tried, after extensive practice. Similar paper should be found and creased, to match, so extensive practice can take place on it, before anything is attempted on the drawing. The tool used to manipulate the fibers should be rounded enough to prevent cutting, but small enough that the pressure can be isolated to the crease. Stone implements are not sufficiently small and a chromed metal implement should be better. Practice on the practice sheet should then reveal techniques that can press fibers back closer to their original position, without undue pressure.
    Hugh Phibbs

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    I'm assuming this is your own work, still in the studio, and not a drawing by another artist that you've purchased. If that's the case, you could try gently reducing the crease with an agate burnisher or bone folder. Try first rubbing through thin paper instead of directly on the drawing, as the burnisher may emboss a shiny spot that will call even more attention to the crease. Test on a scrap of the same paper first so you'll know what the burnished passage will look like. Don't use any metal instruments, because they might leave an indelible mark.

    A burnisher is really handy, by the way, for rough spots from excessive erasing and other corrections in commercial art. Probably not as many artists use them these days as when I was starting out. 

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    Hi Carlos -

    I was wondering what happened as I actually did respond to your email to us at Golden about two weeks ago. So when I saw your questions posted here I thought perhaps you never received our email - and sure enough, in checking my records just now, the reply was accidentally sent to someone else. Aye! Anyway, it was essentially the exact wording that I gave above -and I so glad you took it upon yourself to ask the question again, as otherwise, I would have never discovered my mistake!


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    Koo

    That is great. I would certainly expect this effect considering the thiols in those vegetables, although I have not heard of anyone accelerating the darkening of silver using produce. I have often joked with my students who are bothered by the paleness of their metalpoint attempts that we should make a sulphur chamber to speed up the process. I guess that I will suggest refrigerator refuse in the future ;)

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    Kristin is being a bit modest about our involvement here. She gave a keynote presentation at the conference and I gave both a paper and a workshop.

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    ​Wow....well there were loads of excellent talks. Know that there will be a forthcoming publication released by Archetype Publishing probably in the next year or two...I can really only comment on the things that I learned:
    a) Apparently the use of "flax seed mucilage" was a bit more common during the turn of the century than we previously thought. We have identified this material in Henry O. Tanner's "tempera" paints and a group of Italian researchers have also identified this material being used by several painters working in Venice.
    b) There are and continue to be massive issues regarding terminology with the word "tempera." This is due to the liberal use of the word (as it actually means "to mix") but also the term can change its meaning from one generation to the next depending on all sorts of things. Sorry to bring up Tanner again but as an example his "tempera" recipe basically contains everything EXCEPT egg.
    c) There are all sorts of theories now about how egg-oil emulsions (oil in water or water in oil) form and stabilize. More research needs to be done here.
    d) Basically the most optimal methods of analysis combine some sort of imaging technique that one can use on cross-sectional samples coupled with some sort of chromatography method. Without a doubt, modern tempera paints pose some of the most CHALLENGING analytical obstacles for the science community.
    e) There are many interesting and fruitful collaborations happening in Europe between paint manufacturers/archival paint collections and conservation scientists: Talens and RCE in the Netherlands, the Ca'Foscari University of Venice and Fortuny's archives, and the University of Pisa and Maimeri. 

    But honestly I would simply recommend purchasing the book....as well as "Tempera, c. 1900." 

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    ​Yes everything that Sarah said :) I would simply add however that some of these studies that focus on problematic issues relating to Cadmiums found on paintings dating to the turn of the century (or a bit before) make things sound a bit "doom and gloom." While calcination, temperature, etc., etc. can all certainly play a role in the stability/instability of the resulting pigment, things that have NOT been adequately addressed is a) how fairly invasive restoration procedures may have played a role (lots of water and heat involved with glue/paste linings that can adversely affect certain pigments) b) how the binder may have played a role (we recently published on the Matisse painting cited above and in our research we found that during this period Matisse was also playing around with distemper and casein...it is not altogether impossible that he may have used a few colors bound in these mediums on the Barnes painting as we could not detect ANY fatty acids markers that are commonly associated with drying oils in the CdS paint samples collected from the canvas using ToFSIMS which is rather odd to say the least) and c) the role that pollution may have also played (city air was far more detrimental to the surfaces of paintings during the 19th and early 20th century). I would finally state that Brian Baade and I attempted to replicate the dreaded discoloration that can potentially occur in problematic CdS yellow pigments that were prepared using the "wet process" method under the guidance of Dr. Jennifer Mass. We sent a series of paints out to the GCI to be artifically aged and they came back perfectly fine...so again lots of questions there that remain unanswered. I would say you are FINE to continue painting with Cd pigments...as long as you take proper health and safety and disposal steps of course.

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    ​Hi -

    You are correct that over the last 10-15 years there have been various articles about specific paintings where Cadmium Yellow has undergone changes in color. While the conservation studies are continuing, cases of cadmium degradation so far appear limited to only a very small percentage of the cadmium yellows produced between 1880-1920. On its own, this limitation to such a narrow band of time strongly points to the problems being connected to early manufacturing processes. This would include the presence of initial reactants that were not fully removed, impurities, and the lack of calcination as a final step. This last point is particularly important, since early manufacturers feared that hearting cadmium yellow could cause it to darken. However, that was only true if carried out in the presence of oxygen, while calcining in an inert atmosphere - as was later done - produced a much more stable, harder, and permanent crystalline structure. Without this step the cadmium yellow remained in a more reactive and vulnerable amorphous form, which in turn made it more susceptible to degradation from humidity and light. The lack of calcination would also help explain why these problems are limited to cadmium yellow. All cadmium colors start out as yellow cadmium sulfide, and to make oranges and reds, the cadmium yellow needs to be heated to a very high temperatures along with other metals meant to alter the crystal lattice. Calcination is therefore always needed to make these other shades. Thus it is likely not a coincidence that the introduction of cadmium reds and oranges around 1920, and the adoption of calcination for cadmium yellows as well, coincides with the end of the problematic 1880-1920 period where we find the cases of yellow degradation. 

    For some additional information along these lines we would recommend the following, publically accessible conservation article:

    SR-FTIR imaging of the altered cadmium sulfide yellow paints in Henri Matisse's Le Bonheur de vivre (1905–6) – examination of visually distinct degradation regions

    http://pubs.rsc.org/en/content/articlehtml/2013/an/c3an00892d

    and the section on Cadmium Yellows, Oranges and Reds in Artists' Pigments A Handbook of their History and Characteristics, Vol 1, published by the National Gallery and available for download:

    https://www.nga.gov/research/publications/pdf-library/artists-pigments-vol-1.html

    As for the continued concern about even modern, well-made cadmiums used outside, keep in mind that the conditions needed to trigger the process of cadmium sulfate to oxidize to cadmium sulfide are unique to outdoor environments. Sunlight contains thousands of times the amount of UV and spectral energy compared to artificial lighting, and in particular contains the very high energy, destructive UV-B, which window glass filters out. And of course, there would also need to be a sustained exposure to very high humidity or moisture at the same time. These simply are not conditions that would be expected inside a house or museum. And indeed, environmental conditions do not appear to be the main cause of the few cases examined. 

    Lastly, as to why manufacturers continue to include it as one of the most permanent choices, the fact remains that other than in outdoor settings - and cases of early manufacturing - the cadmiums have continued to do well in accelerated and natural aging tests under indoor conditions. That said, there are certainly alternative yellows one can use - such as the benzimidazolones and bismuth vanadates - that have so far been proven to be equally durable, although often not as opaque.

    We hope this is helpful.

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    Hi Elisane -

    Would be happy to share what we know and try to respond to your questions.

    There is no standard that ties a specific range of acid values to the terms 'low' or 'high', and as you discovered, most linseed oils today will have an acid value below 4. And indeed, ASTM's Standard Specification for Raw Linseed Oil (D 234) actually sets the current maximum allowable acid value at 4. So low and high would be relative to this range, for the most part on a practical level. Certainly in older literature, one can find higher ranges mentioned, but whether that has changed due to modern methods of production -  keep in mind, even cold pressed oils are processed - or changes in the actual cultivated flaxseed, I do not know.  

    Within alkali refined oils, however, one can get quite a range dialed in, from extremely low levels below 1, to standard grinding oils in the 2-4 range, and finally oils with very high acid values of 12-15. As for who sells a linseed oil with high acid value, we would recommend looking at the offerings from Natural Pigments. The only colors that would gain much by using a linseed oil with a high acid number would be reactive pigments, the most common of which would be lead white, but also includes cerulean blue, and cobalt green, among others. See this piece by Natural Pigments for more information:

    https://www.naturalpigments.com/art-supply-education/reactive-pigments/

    Lastly, the better wetting of the high acid value oils can be demonstrated in precisely the way you mentioned - looking at the amount of oil needed to fully wet out a specific quantity of pigment. You also get more viscosity build when combining high acid value oils with a reactive pigment due to the rapid formation of metallic soaps. But to be honest, unless you are planning on making your own lead white, we think you are best off just sticking to one of the standard alkali-refined linseed oils being offered, which should be fine for most cases.


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    Sorry to hear this. It is very difficult to determine exact causes from a single photo. Additionally, there are so many variables beyond adding medium and adhering to what was called “the fat over lean rule” in the past including type of size, thickness or size, type and thickness of ground, paint layering, pigment choice, environmental conditions, and handling. The lower crack appears to be an impact crack. The upper crack may also be from this but it may be a drying crack associated with technique or environment. I will say that when I encountered cracking in my own paintings it was usually when I had applied a too thick ground layer on fabric, even when using a lead white primer. I did use animal glue as a sizing back then and that likely played a role, but I have many works from that era painted on thinner grounds that do not exhibit the same issue.

    Can you tell if the crack continues through the ground to the canvas or if it is only in the paint layers above the ground? This can give us a good indication of which layer(s) are problematic.

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    Sorry for the late response. Richeson recommends casein as an underpainting for oils, and instructs that it can be used over acrylic dispersion painting ground (gesso). They caution against applying casein over any ground containing oil, so that would also include alkyd and traditional "oil gesso" formulas. I think the proposed thin underpainting would be a sound approach, avoiding impasto and broad, thick applications. Ampersand recommends a rigid (panel) support for casein, so I would follow that advice and avoid using stretched canvas, even with thin applications.

    http://www.richesonart.com/products/paints/richesoncasein/richcaseinfaq.html​

    https://ampersandart.com/casein.php

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    I don't think what you are describing is functionally the same as alla prima, because the paint is applied in layers, and adhesion between the strata​ is something that would not be a factor in a single-layer, one session painting. I often recommend that artists not get too preoccupied with the "perfect" time to apply the next layer, though. When I feel ready to paint over yesterday's work, if the surface is touch-dry, and the paint is of thin to moderate thickness, I normally proceed, unless there is some obvious reason to wait (e.g. skinned-over impasto or very "fat" colors in the touch-dry layer). This is unscientific advice based solely on what I do at my easel, however.

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    ​Also, one of the virtues of casein is that over time it becomes insoluble in water. Using watercolors rather than pigments will negate that to some degree.

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    ​Both Ralph Mayer's book and Mark Gottsegen's text list pigments that are sensitive to high levels of pH. We can also reach out to our contact at Richeson to see if they wil answer your question on this forum.

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    ​You probably could? Although I would check the pH of the casein paints you are using...some of your watercolor pigments may be sensitive to higher levels of pH (fresco painters know all about this issue).

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    I just want to introduce a different perspective concerning the reliance on ACMI's AP Non-Toxic statement on labels as we abandoned using that standard many years ago for principled reasons, believing the term "non-toxic' was misleading and promoted a false sense of safety in using materials. While the following is from a piece about the labeling for Golden acrylics, the reasoning would be the same for all our lines:

    "Our concern with the "nontoxic" message was for several reasons. First, potentially toxic chemicals are likely present at some level in all products, regardless of risk assessment; second, it is inappropriate to assume that all possible chronic hazards of chemicals are currently known; and third, personal exposure should be prevented when using chemical products. Over the years, feedback from our customers indicated that reading "nontoxic" on the label implied the paints could be used for things we did not intend; such as body painting, painting with the fingers or tongue, tattooing, and decorating dishware."

    We strongly support the full disclosure of all known health hazards on labels and feel it is important to point out that ASTM D4236 legally requires all art materials undergo toxicological review and carry chronic health hazard and precautionary statements on the label. So always look for those as a way to guide your choices. We just wanted to make clear that not all companies agree with ACMI's use of the term "Non-Toxic" on products.

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    ​I completely agree with Matthew's comments. And would like to stress that just because something is hazardous doesn't mean it can't be used--you just have to know how to handle it properly. You have a great opportunity as art educators to teach artist's about health and safety in their work practices. It's so important that they learn early in their careers. It's unlikely that they will completely avoid all hazardous art materials their entire lives.

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    Artists' oil colors themselves are generally very safe if used according to package directions, especially the colors which carry the AP seal indicating certified non-toxic by a health care professional, safe for all ages. Not all oil colors are non-toxic, but many are. The few colors which require special safety labeling are still very safe to use by individuals who are able to read, comprehend and follow package instructions.

    Linseed oil (the standard oil paint vehicle) is a vegetable oil which is not toxic. Linseed oil does have a characteristic odor some find unpleasant, but the smell is not harmful. Combustion warnings on linseed oil packages refer to the possibility that oil-saturated rags, gloves and steel wool can build heat through oxidation sufficient to catch fire; this is also a possibility with cooking oils. Oil stored in a bottle or jar poses no combustion risk.

    Solvents commonly used with oil paints carry some risks, but these risks can be minimized depending on type of solvent, classroom configuration and equipment, and on number of students. Solvents can be avoided altogether by using water-miscible oil paints. In order to safely work with oil painting solvents, the workspace must be adequately ventilated. There must also be proper receptacles for disposing of waste solvent and medium, and students must understand and follow rules governing what materials are permitted and how to use them. ​

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    Great info. We can report that our current Titanium-Zinc contains 2% by overall weight. Would be interesting, if you are gathering these things, to ask if the percentages refer to:

    - overall weight (oil and all solids)

    - weight of pigments + inert solids

    - weight of pigments only

    - volume of any of the above

    And of course, try to treat this information in a neutral way. While research has not currently identified a safe percentage of zinc, at least one of the principal researchers in this area (Marion Mecklenburg) continues to feel that some as-yet-defined percentage of zinc could be beneficial, providing some film strength to titanium white and acting as a source of active metal ions, which are thought to be critical in the overall structure of a paint film. This is especially true if lead white is not being used in a painting. So always a somewhat complicated picture. In the meantime, transparency in itself is always a good thing and more information is useful for both researchers and artists.

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    ​We thank you very much for sharing this information. We plan to also share your post with folks in the conservation and preservatoin field as this is useful to them as well! 

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    ​This is the first that I have heard about this but my initial take would be to reiterate this quote from the article, "Reaney notes that further research will be needed to determine the long-term properties of the new flax-based paint medium." Perhaps our industry contacts are more savvy about the subject.

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    Kristin’s has written a very complete answer here. What you point out is certainly technically true. Its effect in this instance would probably be minimal and I neglected to bring it into the discussion. I attended when Mecklenburg presented this information.  I was responding to a separate issue and did say that lead is preferable but that what the OP proposed appeared sound. Thanks for bringing this topic into the discussion.

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    ​I will answer on behalf of Brian as well here. He is well aware of the fact that lead can form metal soaps...as are many of the moderators on this forum. However when one is talking about zinc containing films vs. lead containing films there is hardly a comparison when dealing with film strength and flexibility. Zinc is known to cause paint/ground layers to become increasingly more brittle over time (note this has really only been observed in oil-containing films to date NOT acrylics). There are extreme examples of lead soap formation however where the soaps have actually migrated to the surface of the painting and "erupted," causing all sort of unappealing micro-craters to form. But the number of Old Master paintings that possess lead-containing pigments that are in great shape is significant...realize that a certain number of lead soaps are needed to actually impart film strength and flaxibility.While there has been an exhaustive amount of research regarding lead soaps (almost too much imo) we still have yet to learn about what causes these metal ions to migrate to the surface and cause the unaesthetic look I described above. There is some evidence that this phenomenon can be linked to high levels of humidity and/or exposure to higher temperatures....which leads me then to the big question as to how traditional lining and consolidation techniques may have impacted the migration of lead soaps. In the past, restorers would frequently use aqueous-based adhesives combined with heat to consolidate flaking paint and to line paintings. Finally, we still have yet to look into how flooding one's paint with lead driers can affect this issue (again I raise my eyebrow at this given the fact that so many studies have been done on lead soaps....WHY this has not been explored is beyond me). Just wanted to clarify a few things and add some additional info as to where we are regarding the lead soap phenomenon. It is almost an entirely different beast than when dealing with zinc....I would much rather have to deal with an Old Master painting that has a few tiny unsightly micro-craters (that can be inpainted out with reversible conservation colors) than an oil painting that is globally delaminating because it is on a zinc white-oil ground.

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    I don't think the Cretacolor product is made using drying oils, so again I think cleaning and maintenance could be risky.

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    Poppy oil has low viscosity and is less yellow compared to linseed oil, but drying oil in general is a poor choice for this proposed technique, in my opinion. Wax will remain soluble and soft for a very long time, plus it will tend to attract dust. ​Some oil paint sticks are firmer than others, so you may want to at least test them.

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    ​To the OP, re-reading your post I just noticed that you mentioned chalk ground on canvas. Please note that a chalk-glue ground sould not be used on canvas as it is far too brittle for a flexible support. The only time this would be appropriate is when the fabric is completely glued to a rigid panel and the fabric is then completely covered with the chalk-glue ground. In this structure the fabric is acting as an interlayer and is not really carrying the weight of the ground and paint.

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    We view sizing the back of fabric supports as a means to further reduce absorbency of the fabric and seal is off from atmospheric moisture. As Brian mentioned, this work will be done by the rigid support backing in your case. PVA Size underneath acrylic gesso is superfluous in the structure you described. I do, however, advocate for the use of oil/alkyd ground rather than acrylic gesso, as oil/alkyd grounds are less absorbent. Oil colors are formulated to have an appropriate balance of pigment and oil for any given color, which effects color strength, texture, surface quality as well as flexibility of the resulting paint film. Absorbent grounds will through off this balance and generally reduce the flexibility of paint layers. I cannot speak for all oil/alkyd grounds on the market, so I am referencing Gamblin Oil Painting Ground here.

    Kind regards,

    Scott Gellatly

    Product Manager Gamblin Artists Colors

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    Oil pastel is not a good choice in this case, since it's a non-drying medium. Oil paint sticks (e.g. 'oilbars') made using drying oils would be better.

    "Fixing" the charcoal in a layer of oil could lead to yellowing and darkening as the painting ages. If the oil application is very heavy, wrinkling could result, as well. 

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    ​I have sent a note to representatives at Gamblin to weigh in on this.

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    ​Linen will generally contain stronger threads due to the length of the component fibers. This benefit is most obvious when the fabric is stretched on a stretcher or strainer. However, linen and cotton are both cellulose, and under the conditions that you mention, they may be equally stable.

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    I think regardless of what fixative you use, the final surface will be vulnerable if the picture is cleaned. Completely saturating the friable charcoal with oil or painting medium will introduce other problems. In my opinion, the best approach would be to either accept the potential problems, use the fixative of choice and document the materials (maybe frame under glass), or spend some time evaluating other media that might give a similar look, like oil paint sticks which can be varnished. You might be surprised at the range of effects you can achieve, even something with the broken, dry quality of charcoal but more fully bound to the paint beneath.

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    There are a few points here that need clarification. Lead white is the most flexible oil primer and is responsible for the continued existence of many old master paintings. It is the continued flexibility of the lead white oil ground that contributes to the survival of subsequent paint layer. It does not really chemically change later paint layers making them more resilient. This beneficial effect is most obvious when painting on flexible supports as they are the most responsive to changes in relative humidity. You are proposing stretching your fabric over a rigid support which with will go a long way to protecting your work from physical damage due to impacts and will serve as an environmental buffer, slowing down the effects of changes in humidity.

    As to sizing, I see no benefit to using PVA size under an acrylic dispersion ground, although it would probably be fine. PVA is generally used under an oil ground as a replacement for animal glue.

    If it were me I would use an acrylic dispersion medium as a size (see out “Resources” section on sizes) since that will be the binder in the ground and will behave in a similar manner. It also seems to create a more rigid fabric support. Perform a search on MITRA discussing the difference between acrylic dispersion and PVA sizes.

    I wonder why and how you intend on sizing both sides of the fabric. If it were me, I would either adhere the fabric to the pane with the acrylic medium or if you wanted reversibility, which is understandable, I would first size the surface of the panel, allow it to dry, then stretch the fabric over the panel, and then size the surface of the fabric.

    The reason I write this is that it is difficult, or at least laborious, to size both sides of the fabric without creating buckling which is difficult to remove during stretching. This can be done, but it requires that you stretch a slightly larger piece of fabric on a working stretcher that allows access to both sides. You apply the size to one side and then the other while the first is still wet. Let this dry and apply another coat on both sides in the same manner. Let the whole dry overnight. Remove from the working strainer and stretch over the panel before applying the ground. This process is far more likely to produce a planer surface.

    I see no problem with your proposed paint layers.

    Finally, I cannot say if this system is an exact substitute for a painting on a lead white ground, but it does sound like a sound method.

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    ​Hi there and apologies for the delay....in general stretching (with staples or tacks) fabric supports over a rigid support is always a more "stable" option than not stretching over a rigid support. ​But as to the exact chances of ANY slackening occuring over time? This is impossible to know as there are far too many factors to consider...but we would advise stretching over a rigid support for sure. Fastening with tacks will also be a fine way to ensure that slight modifications can be made in the future if necessary. As to your last sentence I am not entirely sure what you mean? Do you mean linen vs. cotton? If you are stretching over a rigid substrate the possibility of one slackening more than the other is really neglible although linen tends to be a bit stronger.

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    I agree that the alkyd white used on this canvas was too binder-rich to be used as a ground. A light sanding with rough sandpaper, followed by wiping of the dust, will open up this layer and make it more receptive to subsequent paint layers. In the future, consider using a true alkyd/oil Ground or an alkyd white made for underpainting (Gamblin makes both of these – our Oil Painting Ground and FastMatte Titanium White. Both of these products, when applied thinly have an adequate tooth to provide mechanical adhesion to subsequent paint layers).

    In regards to Galkyd, being a high viscosity painting medium, it levels brushstrokes and increases gloss. If too much is added to oil colors, early on in the painting structure, the leveled/glossy characteristics of the resulting paint layer may make for a closed/slick surface for subsequent layers to adhere to. Consider this medium “fat” in the Fat Over Lean guidelines – use sparingly in early stages and more as you build up the painting so the structure moves in a “matte to glossy” direction, which will help with adhesion. If you need to paint on a glossy layer, consider a light sanding/steel wool treatment first. For more information on FOL, please refer to our website. It’s also worth mentioning, we also make Galkyd Lite and Galkyd Slow Dry – both speed drying of oil colors, but are leaner than our straight Galkyd.   

    In addition to the FOL info (linked above), please refer to our page on Solvent-Free Painting. As Solvent-Free mediums, by nature, are all 100% fat, they should be used in moderation.


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    It seems to me that paint that can be easily scratched or removed from a ground is a bad sign for future longevity although it is possible that with time the paint will dry and be more resilient. I would guess that the paint you used for your ground was either not absorbent enough or crated a closed film with no mechanical tooth. Conversely, perhaps the scrubbed on oil layer was too lean.

    There is nothing inherently wrong with a good quality alkyd binder. This has been show by decades of use and testing by coatings manufactures. I have generally found alkyd artists paints to be looser with less pigmentation than high quality artists’ oils (this is a very complicated subject on its own as “stabilizers” and thickeners can be added to an oil, or alkyd, to make them very stiff and appear to be super loaded with pigment).  On the other hand, those alkyd artist paints that I have observed created far more transparent and glossier films when compared to an unmodified oil paint film of the same pigment. I have not experimented with Gamblin’s alkyd paint line, which I understand was formulated to be quite lean and a good choice for underpainting. So again, I doubt that the problem is the result of a bad material. Alkyds are perfectly acceptable and useful in the right situations.

    Galkyd may or may not be appropriate for a specific paint effect, but it is a reliable medium for use with oil paint. Artists, like the public at large often have strongly held opinions on subjects that are based on faulty assumptions, misinformation, and biases. Some these become are repeated so often that they take on the air of concrete truth. An example is the often repeated idea that graphite somehow migrates through paint films. This is not and never has been true but it still comes up on forums, including this one.  One of the goals of MITRA is to dispel some of these myths.

    Back to the alkyd containing paint. Zinc is problematic in large percentages in the long term (search the forum for a discussion about zinc white) but its presence would not contribute to the defect you mention.  

    More to the point, I will send a message to M. Graham to see if they would like to comment on this thread. I will also send a message to Gamblin to see if they would like to comment on Galkys and alkyd paints.

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    I've seen something matching this description before, involving layering with oil paint and alkyd medium. In my case, a fresh application of oil paint with alkyd medium was applied over a completely dry layer of oil paint without alkyd. As you describe, the new layer was easily scratched off at first, but later, when the paint became stiffer and not so "fleshy", it was not as vulnerable.

    I wonder if it might be advisable to abrade or lightly grain the first layer when layering in this combination. ​I recall Taubes used to recommend something like this, but his advice was based on independent studio work and not scientific experiment.

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    If one looks at the existing examples of 17th century oil-on-copper paintings that you see in museums, it does appear that it is the superlative surface. Some are so pristine as to look like they were painted this year. This is somewhat misleading. Oil-on-copper paintings tend to be in one of two states of condition, really good, or abominably bad. This dichotomy really has to do with the history of storage conditions. Copper is very reactive. If the painting was stored in a higher humidity environment, it is likely in terrible condition, if in low humidity, possibly great condition.

    This indicates that while copper can be used for permanent paintings, it is not ideal. Copper as a substrate was discussed in this thread:

    https://www.artcons.udel.edu/mitra/forums/question?QID=345

    As Sarah pointed out some of the problems with copper as a substrate are discussed here:

    https://www.academia.edu/1031822/The_degradation_of_oil_painted_copper_surfaces

    and

    http://www.lalibreria.upv.es/portalEd/UpvGEStore/products/p_2102-3-1

    I will not go into what is the perfect surface because that is both subjective and I am not sure that we have tested some of the candidates well enough yet to call one of the contestants a definitive winner.

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    If the question is about which support best ensures durable results, that's a lot easier and less subjective- aluminum honeycomb panels are excellent in that respect. I recall Mr. Gottsegen said he had determined through testing that aluminum provided a terrific pairing with acrylic dispersion primer provided the panel was finely grained with steel wool and washed with denatured alcohol before priming.

    That said, "best" is not going to mean the same thing for all artists. Some artists favor support materials that have known drawbacks. This might be for practical reasons like availability, affordability, the ability to cut panels in-studio, or whether glue joinery and hardware can be easily incorporated. I expect some artists will favor MDO plywood, for example. Others may argue that stretched linen is best for their work, regardless of challenges that emerge as the picture approaches antique age.

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    Great to hear - thanks for closing the loop. Patience, light, and warmth will usiually do the trick!

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    This probably warrants a thread of its own at some point, but would be good to broach the topic that while we often see caveats along the lines of "commercial paints not being made to the same standards as artist materials", and give those caveats ourselves, the actual truth of the mater is somewhat worse - on the art side. I actually think few artist materials are probably tested as rigorously as high-quality commercial ones, especially when talking about acrylic grounds which have over the years, for many if not most manufacturers, been in a race to the bottom in terms of price and hence quality. Some commercial paint systems do extremely well in tests we have done, and many conform to far more rigorous ASTM test standards than those for the art materials industry. Obviously there are many commercial products that don't do great - but the same is true on the art material side. At least in our testing.

    I just worry that we project a picture of art material companies doing rigorous testing to make sure their materials are extremely durable, when I think the reality is that just a small handful of ones do much testing at all. I wish that was different but I will also say that very few manufacturers of artist materials even attend ASTM meetings anymore, which is a sign that there is no broad interest or deep commitment among artist material manufacturers to work on rigorous and scientifically vetted quality standards so that we CAN reassure artists that their materials are durable and appropriate for permanent works of art. Until that changes, I fear we are slipping slowly back to the wild west in terms of quality and even lightfastness of what is being offered in art stores.

    Anyway, it's a complicated situation.

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    ​I think being on a panel you will be fine. Can someone always imagine a 'perfect storm' scenario - probably - but then you can get perfect storms even when using only artists materials. Here I think the risks are truly miniscule. That said, going forward, keeping the commercial housepaints off of the front would probably be prudent.

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    ​Yes I concur with Matthew's statement. This is also why we included similar info (No. 13) in our "Myths" document that can be found in the resources section here.

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    If possible, I would just sand or scrape it off before priming over. Especially if you haven't started painting yet, why not just eliminate any possible problems? House paint is​ formulated for a different type of performance, to a different standard of durability than artists' colors. That doesn't make it inferior, just not always well suited for permanent art. It could be fine, but there may be components of the enamel paint that could affect the painting as it ages.

    Hardware/architectural paints often include additives that are not used or tested in the art materials industry. The polymer base might not be 100% acrylic- it could be styrenated acrylic copolymer, which can be prone to yellowing. Special coalescents may be included so paint can be applied outdoors in cooler temperatures, plasticizers may be present, and it may be formulated to shed particles for a "self cleaning" feature. These are desirable in a paint with an expected 25-year useful life, but not in artists' colors.

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    I think ideally more latex would be preferable, as it clearly is compatible with and would age similarly to the substrate and won't introduce new materials. I have also read that it can be sanded later and that it hides seams well. Since the poster is casting latex, it sounds like they have access to liquid latex which may be used for this. 

    I was reading some forums for movie prop designers, and while some posters complained that new latex can delaminate (aka doesn't have great bond strength) as a join material, others have had good results if they first dampen the bond edge with a mild citric acid solution and then apply the liquid latex (apparently the wetted surface bonds better with the liquid latex than a dry surface). Worth a shot! 

    If the poster does not want to use liquid latex, there are two types of commercial latex adhesives: solvent-based and water-based. Obviously it is hard to say what exactly is in commercial adhesives, but if you are going this route, water-based latex adhesives are preferred, as any solvents in a solvent-based adhesive can dissolve/warp the cast latex panels used as the substrate. 
    Alexandra Nichols

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    ​High alpha cellulose paper and cotton rag paper are made with different plant fibers, i.e. alpha cellulose paper is generally wood pulp that is chemically treated during manufacture, while rag paper is generally cotton.  Rag paper also has a high alpha cellulose content.  As Brian said, both are high-quality and it may just be a matter of which you prefer.

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    The difference between cotton fibers and high alpha cellulose in terms of preservation is likely more of an issue of strength and dimensional stability due to the longer fibers of cotton (in some ways this is a presumption because the fiber length of cotton used for papers can vary from full fiber length to short chopped fibers).

    If the paper receives substantial a layer(s) of good quality acrylic dispersion ground, the ground is providing a good deal of the rigidity and strength. If this is then mounted to an actual rigid support, I am not sure that there would be a real qualitative difference between cotton and high alpha cellulose papers (of equal weight) in terms of preservation issues.

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    ​Matthew, I would tend to agree that your suggested method sounds 1) more easily reversible in the future should that be desired, and 2) easier to ensure that the secondary support was free of defects before adhering the artwork.  The method you're describing sounds similar to lining artwork with a karibari board, actually.

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    ​Here is a response from one of our textile experts: 

    As is so often the case in conservation the short answer is: it depends. It's true that if you compare *fibers* that linen is stronger than cotton because of greater fiber length and higher percent of crystalline structure. But the strength of a fabric is never just about fibers. Fabric is made of threads that can be thick or thin, single strands or plied, tightly or loosely twisted. The fabric can be more densely or more loosely woven. The threads and weave can be more consistent or have more irregularities. All of the structural properties of the thread and weave influence the strength and stability of the fabric. So depending on the threads and weave structures, you could have a specific cotton fabric that is stronger than a specific linen fabric. Also, fibers are often bleached or given different chemical processing during spinning or weaving, and these chemical processes can influence strength (for example, mercerized cotton has higher tensile strength than un-mercerized). With paintings, there are other factors to consider including the way the fabric is stretched and the evenness of the tension. 

    Laura Mina

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    Assuming the artist is handling the mounting procedure, it's less risky to create the panel first and execute the painting on the paper once it's already been mounted.

    I'd like opinions from the other Moderators on this notion: If it's absolutely necessary to execute the art on loose paper and mount the finished work in-studio, it seems to me that one could prepare panels in advance by mounting paper to front and back, and subsequently adhere art to the paper face. I believe this would be simpler and less risky for the artwork, because pasting paper to paper would require a smaller amount of adhesive, and would enable the artist to use a broader range of glues/pastes/films. Plus, the artist would know in advance whether the bond between panel and paper was free from defects before the art was in place.

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    ​This proposal entails both chemical and physical issues. Chemically, plywood must be knot free, to limit lignin emissions and hardwood is a poor choice, since it really is just compressed bark and thus, a high lignin source. Dibond, D-lite, Alumalite, or Pro-lite, are all better options as support layers, since each lacks emissions chemistry. If a paper based board is used, it will be chemically safe, whether it is rag or alpha cellulose, but whatever materials comprises the substrate, counter mounting is a wise step, since paper boards can warp Dibond and may warp hard board and ply wood, if they are not thick enough. To keep things simple, acrylic can be used to mount the paper to the substrate, but its poor initial tack must be factored in.

    Hugh Phibbs

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    ​Matthew's response above is quite helpful here but we have also sent this question along to one of our textile experts. As for the rigid support question, no, there will be no noticable difference (other than color, texture, etc.) once mounted to a rigid support.

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    Both are cellulose fibers which weaken with extreme age due to oxidation, acidity, and the destructive effects of painting materials, UV light and pollutants. Our conservation specialists will no doubt be better able to explain the aging mechanisms.

    In the short term, flax fibers (bast fiber from the plant stem) are stronger and much longer than cotton (boll fiber)​. The longest, strongest flax fiber is produced by spacing plants closer together to reduce branching. Flax grown for seed is spaced farther apart to encourage branching; a fiber crop is still harvested, but it's shorter and rougher than top quality "line" fiber. Lower quality linen thread is slubby, and the resulting "sack cloth" sometimes even has bits of tow in it. To obtain the full length fiber, flax is mechanically grubbed roots and all- never mowed or cut.

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    We do know that acrylic dispersion paints are often superior to PVA dispersion paints but there is no way to say that a particular paint is better or worse without far more info about ingredients and formulations.  

    It does seem fine to mix this paint with acrylic dispersion paints.

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    ​That specific temperature is not great for acrylics or young oil films to be quite frank. You should also consider the impact local heat will have on your ground, size, and support. I suppose you are avoiding something like charcoal for a specific reason...in any case I do not think many of the moderators would be 100% endorsing this material or even this specific technique until more research has been done. However, if you yourself decide to do a fews on your own please share your findings with the group!

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    ​I think I am confused as to what particular benefits these types of pens can offer...apologies if I missed something! As with most materials used in art, if it is difficult to get a fairly clear idea as to the chemical components present in something then it is hard for us to make any endorsements. Even materials of known composition require certain types of testing (I am referring to ASTM testing here) before we can recommend them for specific purposes. Can you please clarify what aspect of these pens you are after in particular so that we can try to offer somewhat helpful advice?

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    ​As long as it did not completely inhibit air flow, it should work.

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    Sarah

    The painter I referenced in my post wanted to work completely wet-into-wet and yet have ample time to work through the painting contemplatively. I have known a few painters who felt and worked this way, but it is in no way the norm.

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    Sarah

    As usual, your post is filled with dispassionate facts.

    I agree that there is just not enough info to draw any real conclusions about the performance of these paints. PVA solutions are rather simple and the Tg is a result of polymer chain length. Emulsions and dispersions of PVA can run the gamut depending on a huge variety of factors and the influence of other ingredients. Some PVAs may exhibit cold flow at room temp and others will not. As an illustration, has anyone ever seen cold flow in dried white glue like Elmer’s (a dispersion of PVA and many other proprietary ingredients)? I have not.

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    I always leaned the painting forward to rest the top edge against a wall or the edge of the painting rack when in art school and in my private studio. If it is oriented properly the surface can even receive a little bit of indirect light to facilitate proper drying/oxidation.

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    I would first attempt to restretch the canvas. It could hurt nothing, as you will need to remove it from the stretchers if you decide to mount it on a rigid panel anyway.

    If this does not work adhering, it to a rigid panel is a viable option. Either cradled birch or ACM would work and BEVA is a good adhesive and is sufficient for this purpose. Your search did not reveal the answers because we included info on this in our downloadable PDF on “Rigid Supports” in our RESOURCES section. https://www.artcons.udel.edu/mitra/resources

    It would be a good idea to read this over as well as our PDF on “Flexible Supports” before moving forward.

    All the best

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    ​Just wanted to follow-up. We are still waiting to hear back from some sources we reached out to, to see if we can get some good references to point you towards. In the meantime, however, see my reply to this similar question where I think I address many of your concerns:

    Vinyl as a Binder

    As for the question of whether adding a layer of acrylic would help, in general we would say yes but keep in mind that it could also impact the aesthetics of the piece, and so some testing would be in order to make sure you liked the results. The acrylic would add greater physical durability and chemical resistance, and if you followed that with a UV protective varnish, you would certainly be covering most of the usual routes of concern with vinyls.


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    I fear there is just not enough information to go on. What type of testing did they do? Following what standards? Can they share the results in a quantified manner? All of those things would be important to give their statement about the vinyl paints as doing better some weight and backing. At the same time, i t is good to realize that vinyls encompass a very wide field of chemistries and polymers and making generalities just isn't valuable because it glosses over precisely those fine points that can make all the difference. Just to take one example of the problem with generalizations, prior to the 1960 most vinyls were plasticized externally - meaning a separate plasticizer was added to a single, or homopolymer, binder - and these generally had issues with the plasticizer being volatile , leaving the system over time, and becoming increasingly brittle as a result. Because of that, more modern formulations have generally gone to a copolymer system where the harder vinyl is joined with a softer resin (hence "co-polymer") to allow for a more stable and flexible system without the concern around plasticizers evaporating away. And of course there are many possible combinations of copolymers, complicating all of this further. But, and here is a good illustration of the danger in just these types of generalizations, a PhD thesis I link to below concluded that the homopolymer formulations in the paints they were studying appeared more stable than the copolymer ones. So.....what can I say....its complicated.

    If interested in pursuing this further you might want to take a look at the following papers, PhD thesis, and book:

    A preliminary study of the composition of commercial oil, acrylic and vinyl paints and their behaviour after accelerated ageing conditions


    The perfect paint in Modern Art Conservation: A comparative study of 21st century vinyl emulsions


    Modern Paints Uncovered

    Unfortunately none of these will provide a definitive answer to your question. The book Modern Paints Uncovered is good to the extent that it covers several case studies involving artwork done with vinyl paints, and so gives some examples of the types of analysis and concerns conservators are involved in.

    In the end, as in so much around art materials, it comes down to the trust in the company, the testing they have done, and how much they are willing to share. Also, keep in mind, the vast majority of research around the durability of vinyls has happened in the context of commercial housepaints, where  the vulnerability of vinyls in exterior applications and UV exposure are well documented. Which is also why nearly every exterior housepaint you will find are formulated with 100% acrylic, while interior paints will use the less expensive vinyls. But these types of concerns might be moot for a work meant indoors.

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    Tilting the canvas forward (if the easel will allow it) helps a lot. ​Covering with a cloth will help, provided something projects out from the canvas or easel to prevent it from contacting the wet paint, and also providing that the cloth itself is not dusty or prone to releasing lint.

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    ​I wouldn't use mineral oil or baby oil for brush rinsing. Honestly, I don't like even the possibility of a non-drying mineral oil getting into the paint. Semi-drying and drying vegetable oils are a different matter, especially when reserved for end-of-day cleanup followed by soap. (Personally, I've gotten best results with vegetable oil bar soap. ) Just be sure not to keep anything at the painting station that would cause trouble if you accidentally dipped into the wrong jar.

    Trying to keep brushes wet by continuously submerging the tufts in oil is not a good practice. Paint will still build up and dry in the ferrule where it can cause the most trouble, and the glue holding the tuft in place may loosen. Just wash your brushes, groom the tuft into shape and lay flat to dry.

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    It should be fine as long as you avoid applying so much acrylic medium that it becomes overly slick and glassy. ​That could cause adhesion problems and possible delamination.

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    Here are my best guesses: According to their site, the manufacturer offers both craft-grade and fine art-grade paints,​ and lists the one you mention among the latter, so they are representing it for permanent art. There are PVA products including adhesives and sizings that meet this standard, so personally I don't see any reason to be particularly suspicious of their claim of durability. Any speculation on plasticizers would be a guess without information from the source, and they might be averse to sharing something they regard as a proprietary secret. It's possible another Moderator will know more about what plasticizers are currently used with vinyl-based emulsions/dispersions. (I think it's pretty unlikely that the formula has gone unchanged since it was used by Dalí.)

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    ​While unusual, because so few go in the direction of slower, you could probably get a painting to stay open a long time if you worked with a slower drying oil, like Poppy, then opt for all slow drying pigments - so eschewing Burnt Umber for, say, a combination of Cadmium Red and carbon black, and so forth. Like I said, it runs counter to what everyone chooses, and forces you off a lot of the earth colors, but it will stay open longer. Just know that many of these slow drying colors form soft or weak films. Its all a tug-awar in a way.

    Lastly, keep it in as cool and dark a location as possible -between sessions  but NOT in your freezer - and leave out the clove oil. Taken together I think doing all these things  might keep a painting open for days. Worth a try perhaps.

    Or one could place the painting in a sealed container filled with nitrogen gas....okay, a little extreme, but.....

    :)

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    Oil paint will adhere to a dry layer of acrylic medium, but it might be a good idea to first evaluate different brands of acrylic primer to see if one yields the results you want. Some are more absorbent than others.

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    In addition to pigment selction, keeping the painting in inirect light, in a warm environment, and with good air flow (not direct sunlight, unless this is only for a very limited time like a few hours, and without the use of strong heaters or fans) will promote a good drying rate. Your choice of oil should be directed by the handling properties and effects that you are trying to achieve. Smooth, long, or easily blended strokes require a less viscous oil or a thin couch of oil to paint into. Broken, dragged effects may require less oil or a stickier, viscous variety. Also, as Matthew mentioned, the type of ground will play a major role in these handling properties as well.

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    Yes, it's certainly possible to achieve durable results using oil colors with a minimum effective amount​ of drying oil as a medium. Since you'll be using manual force to deposit paint, oil with lower viscosity like walnut or raw linseed would work better than polymerized oils like stand and thickened. A "thirsty" or "slow" ground like acrylic dispersion primer ('gesso') will cause strokes to break and drag, so you may want to reserve some cheaper or worn brushes to rough in the frottis when working in oil over acrylic. You may wear out some tufts at first until you get used to the more viscous paint; generously loading the brush helps.

    A "fast" ground like oil or alkyd will facilitate smoother brush movement in the first layer. An acrylic ground can be made less absorbent by rubbing in a very small amount of oil (again, the bare minimum effective amount).

    More neutral-colored oils like safflower and poppy are generally slower drying than linseed oil. You can support faster drying without using catalytic siccatives like Japan Drier by selecting pigments that are strong driers, like raw and burnt umber, which can be added in tiny amounts to blacks and dark neutrals.

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    ​Darn. I see that my fellow moderators beat me to this and did so with some great info. Oh well, here is what I wrote:

    Sorry to hear of your problems.

    If you search this topic on MITRA you will see that I have real misgivings about the use of clove oil in oil paints. I also stated my reservations about using its vapors to keep oil from setting. We know that solvent vapors can penetrate and change even dried oil paint films and it seemed more than reasonable that it could do the same to fresh oil paint. I have discussed the use of clove oil with a number of painters who formerly used a medium similar to yours and they said that even though the paint generally set after 28 days or so, the final film was always rather soft. Anyway, off of my soapbox.

    It seems likely that the natural drying curve of the oil was so disrupted that it is not able to oxidize properly. First, please do not use the spray siccative. There are so many problems with that concept.

    1 It seems like you have three real options. Why not let the painting sit for a while longer to see if the drying was only slowed and not completely disrupted? There can be no harm in this and you can always proceed to numbers 2 or 3 if necessary. You should not paint on top of the problematic paint, or frankly the painting at all, unless it does oxidize. Doing so would set you up for wrinkling, cracking, and possible delamination down the road. I do fear, however, that the lengthy period of time that you report suggests that option 1 is sort of a long shot.

    2 It may be necessary to remove all offending paint from the surface, wipe the surface with OMS and apply new paint.

    3 If you find that too much of the painting is effected, you may need to start over.

    Why not work on another composition until you know whether you need to follow plan 1, 2, or 3.

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    ​I would echo Sarah's caution against use of essential oil of clove in mediums. The main antioxidant component (eugenol) is not standardised from brand to brand, and last time I investigated, it seemed there was a significant difference between the same product from several sources so I think it's probably very difficult to measure reliably. I also agree that later adding a product which accellerates drying will make the paint film very complicated and may yield unpredictable, undesirable results.

    (Regarding the Krylon drying spray, when I inquired, the manufacturer would not explain exactly by what mechanism the product acts on the paint, but I did discover from product literature that it includes an anti-skinning agent used also in industrial paints which prevents a skin from isolating the interior of the film from contact with the air, and reduces the chance of wrinkling when top-driers are used.)

    It might also be worth noting that ambient temperature can affect the drying rate of oils. This time of year, depending on where your studio is located, low temps may just be slowing things down. If you are patient, the clove oil will evaporate and the paint will dry, though the resulting film may have been affected by the presence of clove oil, dependng on concentration.

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    ​First and foremost, I think, is realizing that oil paints in general need light to form a good film. There are exceptions of colors that will still dry in the dark - cobalt blue and raw umber are two that we have tested - but many colors simply will not dry if kept in the dark, and can take extremely long in semi-shadow versus exposure to full indoor light. just to give one example, Cadmium Red Medium in 'regular' studio lighting, 6 mil film, dried in 7 days. When kept in the dark, it took 135! So more than 4 months. In open diffused shadow, it took 16. You can find similar data in Gettens and Stout's Encyclopedia of Artists' Materials:

    https://play.google.com/books/reader?id=X09r_D3mpFgC&printsec=frontcover&pg=GBS.PA40.w.1.0.37

    The graph is small.....but the top dark line is linseed in light, the bottom linseed in the dark. For the dark cured linseed, the tack free stage of drying was not reached for nearly 70 days. Keep in mind this is also linseed oil alone in a very thin film - and of course pigments and other additives can impact it further, both in terms of speeding it up or retarding it even further. The main point is that having little to no light can severely retard and slow up the drying process, and I would not recommend ever drying paintings in dark storage.

    Second, you do not state how much clove oil you added to your medium but we are not fans of adding clove oil into paints. It is an extremely powerful antioxidant and, while you have seemingly had luck in the past, future results (and clearly present ones as well) can differ. If you need to have more open time in an alla prima process, we would recommend trying to use poppy or safflower oil as safer.

    As for what to do now, our experience has been that even the most intransient paint films have eventually dried . The worst we have seen in testing was nearly 6 months, but dry it did. So, have patience, keep it in the light, and if you have a sunny day or two coming up, and none of the colors you used are vulnerable to fading, then having it exposed to direct sunlight would help as well.  We would not recommend trying to spray on or add to the top surface any driers. Trying to force things at this point only risks more complications and potential problems down the line. 

    Hopefully others will have additional thoughts, but that is our advice.

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    Exposure limits aren't really as simple as what volume of a chemical you can use in a day. The simplest answer is that you should reduce your exposure to ANY chemical to the lowest amount possible, with proper ventilation and personal protective equipment (goggles, gloves, respirator). 

    Every chemical you use should have a Safety Data Sheet (SDS) available from the manufacturer. The exposure limit for inhalation will be listed on there as a concentration in air in parts per million (ppm) as either a TLV (Threshold Limit Value) or PEL (Permissible Exposure Limit). These values are the concentration that you could be exposed to --if you worked 8-hours a day, day after day, over a work lifetime--without seeing health effects. Not every chemical has a TLV or PEL. Also, there's no real way to know what concentration is in your work space without instrumentation as it depends on the ventilation, your work practices, evaporation rate of the chemical, etc.

    The lower the TLV, the more toxic the chemical. So for example both Odorless Mineral Spirits and Turpentine have TLVs=100ppm, whereas ethanol is 1000ppm.

    The SDS will also include any information on health risks associated with the chemical (neurological, reproductive, carninogenicity). However, it will be based on available data, and for a lot of chemicals there isn't enough research. So, just because a health effect isn't listed, doesn't mean there isn't one---could be there just isn't any data available.

    As for oil of spike lavendar, there isn't a TLV value and it looks like different manufacturers have different formulations. The one from DickBlick states: "High density vapor irritates respiratory organ, and induces dizziness, headache, anesthesia, slumber or the effect to central nervous system. Spirit of petroleum: Chronical excess inhalation in long time of mist induces inflammation of lung, and may cause fibrosis on pulmonary artery." Which would pretty much keep me from using it in any situation were there wasn't proper ventilation. Another lists limonene as a component, which is a controversial chemical because it's marketed as a "safe and natural" alternative. There is no US exposure value, but European values are 5ppm (remember turpentine is 100ppm and lower is more toxic.) There are lots of "natural" things that are poisonous.

    Inhalation is just one route of exposure (probably the most relavant for artists if you're just using artist's materials in a normal way), but ingestion and absorption are other routes, which is why personal protection and proper work practices are so important. There's no way to know if one particular person will develop a health problem or solvent sensitivity when another will not.

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    Here are 3 references for Stoddard Solvent (mineral spirits):  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2078137/ 

    https://www.atsdr.cdc.gov/toxprofiles/tp79-c2.pdf

    http://onlinelibrary.wiley.com/doi/10.1111/j.1742-7843.2006.pto_254.x/full

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    The 2008 study, Allergic contact hobby dermatitis from turpentine (Barchino-Ortiz L, Cabeza-Martínez R, Leis-Dosil VM, Suárez-Fernández RM, Lázaro-Ochaita P.) details some of the health consequences of turpentine exposure by painters. ('Boo hiss' for the term 'hobby') A 2002 review of toxicology literature for turpentine can be downloaded here: https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/turpentine_508.pdf​

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    Much of the apparent solvent strength of spike oil has to do with its very slow evaporation rate and, therefore, ability to swell/dissolve the lower layers over time. This is really unrelated to whether it is a health hazard or not. We have forwarded your question to our Health and Safety experts/ moderators.

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    If the paint is exactly at its optimal PVC what you are saying probably is technically true.  It does assume that there is not even a bit of a surplus of oil, which is probably not the case. However, I would guess that the effect is not linear and that dilution has little or no deliterious effect at relatively lower radios and rather strong effects at higher. As I said, judicious dilution is probably beneficial in multiple layered systems. This may be more of a function of maintaining tooth in the lower layers and not so much an issue of fat and lean.

    There was a lot of really in-depth work done of drying oil paints in the early 20th century before synthetic materials gradually supplanted them. The positive notion of controlled dilution is somewhat reinforced by early industrial recommendations for the proportions to create a basic lead white primer and house paint. I don’t have a specific volume in front of me but they almost always listed so many pounds of lead white pigment, so much linseed oil, and so much turpentine and not simply pigment and oil. Mayer has similar suggestions for an oil ground consisting of so much Dutch boy lead paste diluted with so much turp to a workable consistency.

    Relating to the subject here, I have found it preferably to dilute lead white to a heavy cream consistency when using it as an oil primer as opposed to simply using the priming knife to create a smooth priming layer out of neat paint. The results of dilution were always slightly drier feeling and more appropriate as a ground layer than my early experiments applied by physical manipulation alone. That is not to say that those early grounds were not useful, they could be very smooth and pristine, they just did not take paint as well as those thinned to a degree and applied with the priming knife.

    It does seem to me that the amount of solvent that is used to create the "initial wash" is often extreme. It would be far better to dilute the paint to to a small degree and then physically spread the paint with a brush (or even better a rag as long as it is disposed of appropriately to avoid spontaneous combustion) I think that some painters believe that their later applications of more robust paint will consolidate the initial powdery layer. There may be a germ of truth in that, but for the most part, this practice is flirting with possible paint delamination. If one creates a wash and then paints on it while it is still wet, the problems you mention would be avoided.

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    ​As to what you can do, and if the work does not contain any light sensitive or fugative colors, put the painting in a place that receives indirect sunlight for a week or so (not directly in the sun unless that is only far a very, very short period of time) and see if some of the yellow cannot be bleached out. If you see some beneficial but incomplete effect, try another week.

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    ​Here is a response from Hugh Phibbs

    Proximity to ligenous cardboard can produce a number of pollutants, peroxides and acids, most prominently, and these oxidants could interact with the chemistry, of the paint, but we have seen so many factors enter into instability of paints, that it is hard to point to anything in the storage materials, in particular. Styrene monomer has long been suspected as a change agent in preservation setting, but the research is scant. What may be safest to say is that this is an oxidation reaction and that the storage setting did little to inhibit oxidation.

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    I am not an expert in preventive conservation, housing, or storage but my gut instinct is that the darkening is a result of dark aging or too much binder, or a combination of the two. However, before suggesting anything, I have forwarded your question to a moderator more knowledgeable about those subjects. I may be off the mark on this.

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    Sorry for the late reply. As to the original comment. Honestly, you are right. That document was written when I was still using the fat over lean terminology on a regular basis and that section was certainly overstated. I have since come over to the PVC school of thought. I will need to edit that section to essentially say the same thing but remove the fat over lean reference, which you rightly criticize. There are other realistic reasons to thin lower layers and add less solvent to upper layers in multiple layered systems.

    However, I do sort of question the idea that heavily diluted paint has the same binding properties (different than fat or lean). The concept makes sense in theory, but it does not work exactly the same in practice. If it did, you could take a given amount of oil paint, thin it with a very large amount of solvent (let’s say OMS here to avoid the turpentine issues mentioned above) and apply it as a toning layer on a ground. In theory, this should be as well bound as neat oil paint physically distributed by the brush to a very thin layer (to the degree that is likely in practice and not a theoretical, unlikely degree).

    In practice, though, it is very easy to add enough solvent to oil paint and create a film that can be easily rubbed off on your finger. We see this all of the time in modern and contemporary paintings. Sometimes they cannot even be cleaned in any manner because any physical manipulation dislodges original pigment. Yes, an absorbent ground would exacerbate this making it more likely that the binder would be drawn into the ground leaving the paint underbound. This may be a major cause of the apparent discrepancy. I have, however, seen the same effect on relatively nonabsorbent grounds but have not preformed any real scientific tests. So while I completely with your take on all theoretical grounds, there is still seems to be a difference in the bonding strength between neat oil paint and oil paint thinned with solvent.

    However, I still do need to remove that phrase, as it is misleading.

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    ​I'm sure our scientist Moderators will correct where I am in error, but as I understand it, fresh, pure gum spirits of turpentine that has not been exposed to the air will take up oxygen more readily than old stock from an open bottle. Because of this, fresh turpentine mixed with oil paint will increase available oxygen in the paint film and support through-drying (though not as a catalytic siccative). Old turpentine that has already oxidized will not impart this effect, but will still thin paint. Stale turpentine containing oxidation products has been shown to be more irritating to the skin, as well.

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    While I wasn't involved in composing the linked document, it may help to consider the effect of solvent on viscosity of the vehicle, and how reducing viscosity impacts the envelopment of pigment by the vehicle.​ Oil paint isn't just a simple mixture and proportion, it's a homogeneous dispersion with each pigment particle enveloped in oil. Naturally, paint that has been thinned excessively would lose the orderly distribution of pigment gained through milling. Excessively thinning oil colors results in paint with a powdery appearance due to unbound pigment. It also occurs to me that a thinned vehicle could be taken up more readily by an absorbent ground, and I imagine some is even wicked away by a semi-permeable palette.

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    I understand the appeal of historical theories about painting methods and materials, but the need for accountability to collectors compels me to use modern, reversible varnishes that facilitate easy maintenance and cleaning of finished works.

    Charles Locke Eastlake is often the source for notions about use of oil varnishes throughout history. Eastlake's theories about the use of oil varnishes by the Old Masters were influential, and are still referenced today despite even Eastlake himself remarking often at the apparent defects in paintings where oil varnishes were used. Eastlake wrote about the comparative tendencies of different fresh, semi-fossil and fossil varnishes to yellow and darken, and theorized that earlier painters employed strategies to compensate for darkening, or even use it deliberately. It's important to remember, however, that Eastlake wrote and worked at a time when a dark, yellow cast in paintings was associated with antique age and was often considered aesthetically pleasing. http://www.mediafire.com/file/3mwymy4r2oo/methodsandmaterials_Eastlake.pdf

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    ​So recipes for oil-containing varnishes go back quite far (Theophilus writes about them in the 11th c but they were likely in use even earlier) and it is possible that oil alone was used on occasion as a coating for painted surfaces. Eventually the Old Masters sowly transitioned to spirit varnishes around the 15th c however it is clear that oil-containing varnishes continued to be used here and there. But as we know not everything the Old Masters practiced or used stood the test of time. Oil-containing varnishes are a perfect example of this....they can turn horribly brown and darken, obscuring the original palette beneath. Perhaps even worse they cross-link, meaning they become impossible to safely remove from oil- and/or resin-containing paint layers. Finally, an unpigmented stand oil film will remain tacky for a very long time, inevitably attracting dust and grime. I hope this somewhat answers your question. 

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    ​One more thing. While many people seem to assume that GAC 100 or acrylic gesso somehow seal the surface of a panel, they are actually really poor moisture barriers, which is precisely what you want to try to have on those exposed sides. For that we would recommend following our guidelines in the following article on Preparing Panels for a Life Outdoors

    http://www.justpaint.org/preparing-panels-for-a-life-outdoors/

    Although the focus is on exterior use, it would still represent a superior moisture barrier to many alternatives. You might also, for interior use, take a look at pigmented shellac primers, such as BIN. See my posting in a different MITRA thread on sealing hardboard with shellac for some references to support that option:

    https://www.artcons.udel.edu/mitra/forums/question?QID=379

    Okay, hope that helps.


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    Thanks Brian, but this happens to actually be a case where questioning us might be in order! I feel I can share that we are actively looking at changing our stance on plywood, or at least modifying it, and are just now plotting to do some testing and more thorough research. And, while the referenced article was published in Just Paint, our newsletter, the research and views were from Elaine Salazar, of Ampersand, who certainly has a long relationship to these issues and materials, thus we would continue to give them some consideration and weight. That said a few things have started to chip away at our own confidence in plywood. One, is having some cases come to us with cracking in the ground and paint layers that seemed clearly associated with the veneer used on the underlying ply. Second, a comment from an conservation scientist we were corresponding with caught our attention when they stated they felt that plywood was unsuitable for permanent works of art, and finally - while we rarely give Wet Canvas posts a lot of weight as a reference - this following one felt exceptionally well researched in terms of citing conservation research and studies from the Forrest Products Laboratory, and the points made are in line with your own comments above: 

    http://www.wetcanvas.com/forums/showpost.php?p=20442188&postcount=6

    So, all of that combined definitely has us taking a renewed look at alternatives, such as other types of composite, engineered wood supports, and of course aluminum composite panels remain seemingly ideal. We should also mention that internally we rely on MDO (medium density overlay) for our plywood supports, as do several of us in our own work. The resin impregnated paper surface does seem to solve some of the issues of grain and provides a smooth surface, but even there I think more research might be warranted, even though it appears to pass muster as an approved material for use in storage cases in museums.

    Anyway, wanted to chime in on that one aspect at least.


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    ​Hi -

    You question was passed along to me and I would be happy to gather some information for you. To do so I want to be able to touch base with our chemists and formulators in our Lab, so the earliest I can post that would be Monday. So hang tight - but promise will get you what information I can.


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    I would not contradict those at Golden as they tend to do substantial experimentation before making claims about performance. What they state is certainly true, it is important to follow those steps to create a panel that is less likely to develop cracks or checks. I would add though, in my experience and years of examining paintings and student works, it is extremely common to see some degree of checking in grounds (acrylic dispersion and glue based) on ply panels (when there is no interlayer of fabric or film). Plywood is made by basically shaving wood off of the trunk of a tree to produce a very long continuous sheet (sort of like a roll of toilet paper). This sheet is cut, flattened, and adhered, to another sheet, usually at a 90-degree angle. This creates a panel that is far less likely to warp but this flattening does introduce stresses that tend to reappear as checking along the grain. A well-sealed ply panel with a substantial acrylic dispersion ground layer may not develop these defects. Additionally acrylic dispersion grounds are far more flexible than glue grounds and would likely show less checking than glue-based grounds.

    However, even for acrylic dispersion grounds, I tend to recommend gluing a fine fabric to the sized panel, applying an additional layer of size on top of the fabric after it has dried, and put the acrylic dispersion ground on the fabric layer. This resembles the methods used by the Early Italian tempera painters to diminish cracking in their true gesso grounds on panel. Others may have a different take on this.

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    ​Hi again -

    After reading through various blogs and posts, I thought I would add a couple of finds. One is from a framer who sprays traditional gesso and adds salt (a tablespoon to 20oz) as a anti-gelation additive to slow down the setting of the gesso, as well as a splash of alcohol as a wetting agent. He also emphasizes strongly - as did various other posts by people who spray - that it is critical to apply the first coat by hand and make sure it is well smoothed out as this is where the pinholes get started and then continue telegraphing upward. Also a couple of places mentioned addition of a few drops of linseed oil, which of course would act as a defoamer - in acrylics one can use mineral oil for the same purpose. But it would need to be well emulsified. Okay, just wanted to pass along those two suggestions. traditional framers seem a good source of info as spraying seemed to crop up as a more common tool - perhaps because of the intricate textures of a carved frame?

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    Hi Koo -

    "

    "Flow Aid" is not a Golden product, but is rather a medium made by Liquitex. We do not know if there are any restrictions on spraying or if it would be effective for this use, and would recommend reaching out to them directly for more information.

    However, you might have been speaking about our Acrylic Flow Release, which has since been renamed Wetting Agent. If so, we would NOT recommend using it for any spray applications. In fact, on the label and the Tech Sheet, we state: "WARNING: EYE IRRITANT. INHALATION OF SPRAY MIST HARMFUL. DO NOT SPRAY APPLY."

    In the meantime, I can pass on the question to some of our other folks in the Lab to see if there are more insights or suggestions and if so will report back.

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    ​The issue of the alteration of lead white due to the presence of hydrogen sulfide air pollution is less a concern today than it was when industrial countries burned coal. I am not sure if the statement by Church is accurate science; I cannot see how sulfide pigments can prevent this type of issue ocurring in the presence of this type of air pollution. Anyway, I think you may be overreaching by being concerned by this issue.

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    ​Hi -

    As Kristen mentioned, this is an area I have partly covered before and would also point you to the same thread. That said, I am also happy to touch on your questions here as well. In terms of the issue of oils over acrylics in general, we feel this article can serve as a good introduction and the points it covers should be applicable to any high quality professional brand of acrylics:

    Using Oils with Acrylics

    As for your specific concerns:

    Adhesion: As the above article points out, we feel that oils will adhere to acrylics and all our testing has supported this. However let me throw in a few caveats. One, we know oil paints containing zinc have been linked to cases of delamination, including from acrylic grounds, and would recommend not using any oils that contain zinc - especially in an underlying layer. Two, while we believe and have tests showing that oils adhere to even glossy acrylic films (for example, oil grounds adhere well to our GAC 100 used as a size) we also know that in ANY system, including oils to oils and acrylics to acrylics, matte and toothy surfaces provide maximum adhesion. That is simply a function of increased surface areas and opportunities for mechanical adhesion through a 'lock and key' mechanism. Because of that we err on the side of caution and recommend keeping the acrylic underpaintings as matt as possible. If you have a variated surface, with differing degrees of absorbency and sheen, then applying a layer of a matte medium can serve as a translucent ground for the oil paint and provide a more uniform layer to work on.

    Drytime between acrylic and oil: We know that in even a thin film of standard acrylics will lose moisture and other evaporatives, and start to approach an equilibrium with the environment, over the course of a couple of weeks. So we tend to recommend waiting two weeks as best practice, assuming the layers are the typical normal brushstroke thickness. Anything that is applied very thickly or uses very slow drying acrylics, such as Golden's OPEN, would need longer and could easily take a month or more. That is 'best practice'. At the same time, it is also true that the vast majority of moisture is lost from a thin film in the first 72 hrs and we feel that if you waited at least 3 days that any increase in risk is very minimal. But its not ideal. Besides, patience is a virtue!

    Best thinning medium: Don't be afraid of water is the first thing to mention. At least in our own testing of our paints - and we assume this would extend to other professional quality acrylics - we have confidence that one has a very durable film even after thinning up to 1:1 with water. So if needing to adjust viscosity and get more flow, water will get you there faster than any alternatives. In terms of mediums, we would recommend going with matte mediums to provide that additional tooth that is helpful for subsequent adhesion of the oils.

    Ideal substrate: An inflexible panel is by far the best option. Aluminum composite panels would be high on my list, as well as some high quality plywoods and, for smaller works, hardboard. This is really more about the oils than anything else, and would be true even if painting only in oils, even without multimedia concerns. 

    Watercolors for underpaintings: I don't know of a lot of testing around this specifically but I do know it is mentioned as a technique in some 19th century works in Leslie Carlyle's The Artists' Assistant. Overall I think if it is kept thin and on an absorbent surface it should be fine. But others here might have additional thoughts.

    Hope this helps!

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    I really like Acrylic Gloss Gel Medium for this application. I coat the fabric and panel separately in advance and allow both to dry before mounting with an adhesive coat of gel. (Fabric is stretched for sizing.) This way, I can mate two acrylic-coated surfaces for an excellent bond with very little shrinkage of the fabric. On the rare occasion any blisters or unbonded corners develop, a warm iron tacks down the loose bits once the adhesive is dry. 

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    ​I am sure some of our other moderators will chime in but until then you might find some of the information on this related thread of interest (particularly comments submitted by Sarah Sands): https://www.artcons.udel.edu/mitra/forums/question?QID=380

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    That is rather acidic and would likely cause some degree of acid hydrolysis. There are PVA sizes that are buffered to be neutral. Two of them are Lineco pH Neutral adhesive and Gamblin’s PVA size. Acrylic dispersion gel mediums are also good choices. We discuss the subect more fully in our Adhesives and Sizes  downloadable PDF found on this page https://www.artcons.udel.edu/mitra/resources

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    Whereas solutions of sulfuric acid and lead(II) acetate react to form solid lead(II) sulfate and a solution of acetic acid, this simply increases the impurities in the product. Where did you read that lead sulfate is beneficial? I have never read this and would be curious to know the reference, otherwise I have never encountered this in literature.

    Georg Zerr writes in A Treatise on Colour Manufacture (page 115) about testing for the presence of lead acetate:

    "It is very easy to ascertain whether white lead contains lead acetate by pouring a small quantity—about twenty to thirty grms.—into a porcelain basin with water, and heating it carefully over a flame, the whole being kept stirred. The liberated water vapour will have the characteristic smell of acetic acid and redden moistened blue litmus paper, owing to the presence of that acid. The aqueous solution will deposit a white precipitate of lead sulphate on the addition of sulphuric acid."In the preceeding paragraph he remarks:"White lead that has not been sufficienlty purified from adhering lead acetate has the sometimes troublesome property of making paint dry very quickly. A paint of this kind, containing about 6 to 7 per cent, of linseed oil, will on being kept get hard and lumpy, requiring protracted treatment to make it fit for use again."

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    ​A lot of moving parts to this discussion but let me jump in and provide some additional thoughts.

    As simply a separate question, divorced from the use of wax and speaking in general, we feel that oils will adhere to acrylics and all our testing has supported this. However let me throw in a few caveats. One, we know oil paints containing zinc have been linked to cases of delamination, including from acrylic grounds, and would recommend not using any oils that contain zinc - especially in an underlying layer. Two, while we believe and have tests showing that oils adhere to even glossy acrylic films (for example, oil grounds adhere well to our GAC 100 used as a size) we also know that in ANY system, including oils to oils and acrylics to acrylics, matte and toothy surfaces provide maximum adhesion. That is simply a function of increased surface areas and opportunities for mechanical adhesion through a 'lock and key' mechanism. Because of that, we tend to err on the side of caution and are one of those companies that often do suggest using a layer of acrylic matte medium as a form of translucent ground. We do not use the term 'clear gesso' but are aware that other companies do - but keep in mind those are not really clear but are essentially variations of a matte medium or a slightly more translucent version of molding paste. In any case, the role this is playing is mostly to make sure you have a uniform surface to work on top of, avoiding the inevitable issue of having an underpainting that is more absorbent in one place than another, or - which is often related - has a range of different sheens. Plus we never know which paints one might be using, so having this translucent ground layer helps assure that the paints are anchoring to one companies' product, making it easier to troubleshoot. For more information about our thoughts on oils adhesion to acrylics, please see the following article:

    Using Oils with Acrylics

    Moving on to the question about the use of cold wax techniques on top of acrylics, we would approach that with a lot of caution and would need to be comfortable both doing some testing as well as simply taking on a host of unknowns as this is simply not an area that has been looked into, as far as i know. What I can share is that we know encaustics do not adhere well to acrylics, except with highly textured grounds, or onto special very absorbent acrylic gessoes formulated specifically for encaustics. The reason is simply that wax, in and of itself, does not adhere well to other surfaces unless it can penetrate deeply into it and form a strong mechanical bond. While obviously encaustics are all the way on one end of the spectrum, adding wax to oils simply lowers its adhesion as well, not to mention increases brittleness, solvent sensitivity, and vulnerability to both cold and high heat,  The roughly 30% addition you mention would be at the furthest extreme limit of what would be advisable and we think you would be better using as little wax as possible if wanting to have the best adhesion.  If ultimately the desire to use wax is to have a waxy surface, you might consider forgoing it as an addition into the paint and using it instead as a final layer on top, to impart that type of sheen. 

    Lastly, if comfortable taking an approach of simulating the wax look using acrylics, that would make for a simpler process with far fewer potential issues and is something we have published about:

    Creating an Encaustic Look with Acrylics

    It should go without saying that sharing these articles are in no way meant to promote Golden's products. The approaches will work just as well with other companies, so take it in that spirit.

    Hope that helps to round out some of the thoughts already presented.

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    ​I am not aware of any research that provides a definitive answer to this question, however, the old Dutch method or stack process of making lead white initially produces lead acetate, which usually exists in excess in the final product and is unstable in the presence of carbon dioxide. Every manual on the manufacture of lead white stresses the importance of washing the lead white to remove limpurities. Although not specifically stating the importance of removing lead acetate, I believe that this is an important aspect of levigating the pigment to remove all traces of lead acetate, which is indicated when the wash water no longer turns blue.

    I beleive the purpose of Bouvier's instructions of stirring a slurry of lead white in water would cause the finest pigment particles to rise to the top where they can be decanted and used in fine watercolor techniques.

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    Thanks Scott. Given this info perhaps I could add an additional suggestion if one wants to be absolutely scrupulous with technique. The fast drying nature of the solvent free gel means that in a mixed medium context it would be better to either use it in the lower layers or add it sparingly to the upper layers. This is to maintain the preferred idea of faster drying lower layers and slower upper to prevent cracking, etc.

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    Gamblin Solvent-Free Gel and Solvent-Free Fluid are mixtures of alkyd resin (soya oil-modified, long chain alkyd resin) and safflower oil. Think of the alkyd resin as a pre-polymerized oil – highly compatible with other drying oils, just further along in its drying process.

     

    I see no issues incorporating these mediums with other drying oils (linseed, safflower or walnut). They are all similar in their oil (“fat”) content – 100%. Do keep in mind that the Solvent-Free mediums will be faster drying than any of the aforementioned drying oils.


    Scott Gellatly
    Product Manager
    Gamblin Artists Colors

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    ​There should be no problem doing this as long as you observe rational layering practices (less or no medium in lower layers, etc.). Will will send this to Gamblin to see if they have anything to add. 

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    First, I need to be honest; I have no experience with clear gesso. I am immediately annoyed by the use of the term “gesso” for such a material but I understand that I am never going to win that battle.

    It is my understanding that clear gesso is intended to allow for a sizing/ground that allows the artist to exploit the color of the substrate and not obscure it with a more traditional colored ground.

    I am confused as to how this would promote better adhesion between acrylics and oils. Is the thought that the clear gesso adds some texture/mechanical tooth for the oil layers to adhere to? It seems to me that to remain clear, the amount of bulking filler and texturizers would have to be very low and unlikely to offset the diminishment of surface texture caused by the addition of the clear gesso layer.  Generally, the more layers, the more likely there can be adhesion problems.

    Others more familiar with the material may be able to comment with more authority.

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    I am not sure that I can provide the final word on this and will reach out to others for confirmation. I do have a few thoughts about the subject.

    First, residual lead acetate and other lead products left in poorly washed lead white are responsible for the fast drying reputation of lead white. Lead oxide, lead tetroxide, and lead acetate all make oil paints that dry very fast. Lead white is actually quite average in its drying speed.

    My guess is that the reactivity of lead acetate makes is a poor component in lead white paint. I would also bet that it contributes far more mobile ions that are more likely to contribute to lead soap defects. It may also be more prone to other changes.

    As to whipping lead white in water and using the foam, my guess is that this was a form of levigation. A watercolorist would want the finest pigment particles. The stack lead white process produces a large range of particle sizes unlike modern precipitation processes. The whipped mixture would allow the finer lead white particles to remain longer in the water than the coarser particles would quickly fall out of solution.

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    Matthew, you beat me to this. I agree with you on this and the need to understad what is meant by oil crayons.

     Paint that contains as much as 1/3 wax should probably not be considered traditional oil paint. It would be better to avoid varnishing such works as the solvents required to remove that varnish in the future would very likely bit into and remove some of the original paint.

    If you decide to varnish, make sure that it is a varnish that is known to yellow the least and make sure that you record your paint media and varnish on the reverse of the painting (on the stretcher bars, etc) to make sure that future conservators understand what is in your painting and avoid testing the varnish with solvents likely to harm your paint.

    Oil paint with more than 1/3 wax should probably be considered an oily encaustic medium rather than the other way around.

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    There are a lot of variables in this proposed application. By "oil crayons" do you mean oil paint sticks, or oil pastels? This is important, because oil paint sticks dry like tube paints, but oil pastels are made using a non-drying vehicle and will stay soft indefinitely.

    Most of the time, it's possible to apply oil paint directly over acrylics, which generally offer enough absorbency and texture to support adhesion. A layer of clear "gesso" might unify absorbency and tooth across the entire surface, so that could be a good strategy if there are thinly painted or very slick passages in the underpainting.

    1/3 wax by volume sounds like a lot. Personally, I wouldn't apply a solvent-borne varnish over paint with that formula due to concern that it may be too soluble even when dry.

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    I agree fully with both Brian and George's statements on Gilding and Panel preparation, and gilding materials. As to the questions #2 Why can't you burnish oil gilding? The answer is about materials used, the burnish or shine comes from the direct contact of burnisher/agate stone with the Rabbit Skin Glue, as that is the surface material that is actually taking the "shine". Do not allow the burnisher/agate to touch the oil gold or oil gilding, for if it does, the gold will come off, and the surface could brake down.  

    ​#3 Gilding a Ram Skull; first there are questions; is this a found object or store bought, as there may be chemicals used to remove sinew etc. that can effect the surface preparations. One can test as "Bone" is fairly porous and a simple test of brushing rabbit skin glue directly on a small area, allow to dry 2 hours, and with a sharp knife scrape the edge of the rabbit skin glue, if it should peal off switch to Oil Size for your size/mordant, if it adheres well, cover the entire skull inside and out with 2 coats of warm RSG and allow to dry. You then can treat the skull like a frame or panel and begin using "Gilder's Liquor" warmed and brush small areas and gild directly. Allow a minimum of 3 to 4 hours after gilding including removing any skewing's and applying and regilding misses before "Burnishing". Please remember that using an agate stone requires a "practiced hand" not too soft or to hard, bring the "shine" up consistently and when completed, seal with a "Clear Overcoat Varnish" by Ronan "Topcoat Clear" gloss which is a water clear non yellowing acrylic enamel for use over gilded surfaces.  Martin Kotler

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    When I assign a gilding project to my classes, they generally follow this procedure.

    Sand panel with 220 grit paper

    Dissolve the animal glue in a double boiler. Apply a thin application of animal glue size to all sides of the panel (they work on wooden panels as opposed to ply or hardboard). You may only want to only size one side but this may cause warping unless the panel is braced on the back. If you size both sides, you may want to paint the back after finishing the front to isolate the glue from the environment.

    Let dry and apply a second layer. Let dry.

    Warm the animal glue in the top of a double boiler. Remove top from the bottom water-containing pan. Make the ground in the top. Gently stir. Apply as many layers of chalk/gypsum and animal glue ground to the panel as can be accomplished in one long session. Breaking this up into multiple days promotes pin holes in the ground. When the ground become too cool, and gels, warm the bottom water-containing pan in isolation from the ground-containing pan. After the water is hot, remove it from the heat source and place the top, ground-containing pan on the bottom of the double boiler. Never heat the ground directly or indirectly ON the heat source. It should only be made fluid by putting it on the pre-warmed water. Over heating the animal glue containing ground is the surest way to promote pin holes in the ground.

    Let dry. Sand smooth.

    Mix bole with animal glue. Thinly and smoothly apply the bole to places where you intend to gild.  Apply a couple of fine layers until it is opaque. Let dry.

    Polish the bole.

    Water gild.

    Burnish when the ground and bole are ready.

    Apply an imprimatura, etc. layer to regions to be oil painted.

    Allow to dry.

    Paint away                                                                 

    The brilliance of burnished gilding is diminished by a varnish. If that matters to you, I would only varnish the oil painted portions.You could paint on the areas of the panel that only have animal skin glue as long as you take the color of the panel into consideration.                                                                                                                                                                                      Oil paint does not adhere to glass well at all. Reverse painted on glass paintings are the bane of all painting conservators. If one was dead set on doing this, I would suggest sand blasting the glass first so that there is some mechanical tooth but this may still be problematic.

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    Rublev Colours Tempera Ground is based on a vinyl acetate ethylene (VAE) dispersion that allows us to formulate it with a very high pigment volume concentration (PVC), much higher than is possible with acrylic based grounds. For this reason it has much better absorbency and sandability properties than acrylic grounds and gets as close as possible to the PVC of traditional gesso grounds, which is the type of absorbency desired for gilding. We have tested gilding on this ground that can be applied to either wood or ACM. However, to achieve “bright gold” or very high gloss burnished gilding requires very smooth surfaces as Brian has pointed out. This is possible by applying multiple layers of bole (red clay) in animal collagen glue. The bole can be sanded and then burnished to achieve the smooth surface required and the animal collagen glue in the bole can be activated to adhere the gold leaf. Although some gilders apply gold leaf by breathing on the bole, we have also found that applying a “gilding liquor” allows better activation of the animal collagen glue.

    Rublev Colours Tempera Ground is a very absorbent ground and hence is excessively absorbent for oil paint (and hence why we named it "Tempera Ground" which requires very absorbent surfaces). This can be easily corrected by applying a toning layer or an imprimatura of oil paint. We also recommend adding a small amount of bodied oil to this paint to enhance the “hold out” properties of the oil paint.

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    That ground is a very lean polymer dispersion ground. Geroge knows his stuff and it is probably appropriate for tempera. I am not sure that I would recommend it for burnished gilding, though. It would dry water insoluble meaning that it cannot be reactivated during water gilding, and would not take a burnish. Your bole would be burnin\shable as long as it is bound in animal glue, but this layer is usually very thin and the burnish would be less than normal. I will ask George to comment here, as perhaps there is something in the formulation that I am missing that makes it appropriate for this purpose.​

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    Sorry to confuse you. There is no “unmodified” ground that is appropriate for burnished gold (meaning water gilding) and oil painting. The water gilding requires a chalk or gypsum/animal glue ground with or without a bole/animal glue layer) to allow for burnishing. These grounds are very brittle and need to be applied to panels and not canvas. Additionally, such a ground is excessively absorbent for oil painting. Traditional gesso and chalk glue grounds do contain animal glue and are, therefore, reactive to changes in humidity. They can be very "archival" as evidenced by paintings and objects in museums containing these materials that are 700 and more years old. More to the point, unlike general easel painting where we have numerous grounds which are less sensitive to the eviroment

    Sorry to confuse you. There is no “unmodified” ground that is appropriate for burnished gold (meaning water gilding) and oil painting. The water gilding requires a chalk or gypsum/animal glue ground with or without a bole/animal glue layer) to allow for burnishing. These grounds are very brittle and need to be applied to panels and not canvas. Additionally, such a ground is excessively absorbent for oil painting.

    Traditional gesso and chalk glue grounds do contain animal glue and are, therefore, reactive to changes in humidity. They can, however, be very "archival" (I dislike that word but understand what you mean) as evidenced by paintings and objects in museums containing these materials that are 700 and more years old. More to the point, unlike general easel painting where we have numerous preferable grounds which are less sensitive to the environment, water gilding really requires an animal glue binder. In this instance, the oneness is on storing the work in the proper environment.

    This problem is easily surmounted in the following manner. Prepare your whole panel with a chalk or gypsum/animal glue ground. If desired, coat all areas to be gilded with bole/animal glue. Apply gold and burnish. Then coat all areas to be painted in oil with a layer(s) to diminish the absorbency of the ground. In the Renaissance, this was done by applying a few coats of animal glue and then an imprimatura (basically, a fatty oil paint layer containing white). This is still a viable method, however, today this could be accomplished by cutting the absorbency with an acrylic dispersion medium, shellac, the judicious application of a drying oil (perhaps with a bit of catalytic drier added), or perhaps best, with an alkyd paint or medium layer. One need to be cautious to make sure that this layer only cuts the absorbency and does not create a slick surface that may promote paint delamination.   

    As I wrote previously, there are a few systems out there for creating the appearance of burnished gold that do not rely on animal glue grounds. I am not experienced with these materials, but will forward this query to a moderator who may have more knowledge about these systems.

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    To be honest I doubt that you would need to do any sanding - the shellac pentrates easily - but if you did it would be the lightest of touches.. However, I would likely wipe down the surfaces with alchohol first just a a form of degreasing.

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    ​In terms of amount of coats I would follow whatever the directions state. I know when I work with BIN Original, which is likely the brand of pigmented shellac primer you saw, I apply two coats simply because I always feel more confident that everything has been covered and that the film is more even throughout. In truth two coats will still appear quite thin, so no fear that you are building up an appreciably thick layer. And with shellac, because it does grow more brittle with age, keeping things thin makes sense as well. Finally, would not thin it further - BIN comes quite thin and ready to use already, just make sure to stir it up thoroughly.

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    ​Sarah. Thanks again for your fact filled response.

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    ​Oddly enough we received a question yesterday about using clear shellac as a sealer against moisture, so given its relevance let me share the reply here as well:

    "Shellac is often used by woodworkers as a preferred sealer for wood as it is not waterbased and so will not raise the grain, dries very quickly. However we would opt for a pigmented shellac – such as BIN’s Original - as being a better water moisture barrier and take that information from the Forrest Products laboratory, which are truly the experts when it comes to research into wood finishing and protection. You can find information about their recommendations in various places. Here is one link to a list that includes pigmented shellac, which rates surprisingly not all that far behind even a two part epoxy:

    https://www.fpl.fs.fed.us/documnts/techline/protecting-wood-from-humidity.pdf

    Another document supporting pigmented shellac over clear can be found here – a much more technical document to be sure but will quote the relevant part from page 14:

    https://permanent.access.gpo.gov/websites/www.fpl.fs.fed.us/documnts/fplrp/fplrp462.pdf -(Note: MEE stands for Moisture Excluding Effectiveness. The higher the number the higher the percentage of blocking moisture.)

    'The low values of MEE14 for latex finishes stand in contrast to those of the shellac-, varnish-, or paint-based finishes that we evaluated. A white shellac (alcohol solvent) (finish 23) with an MEE14 of 73 percent for six coats was less effective than a pigmented flat shellac (also alcohol solvent) (finish 60) which had MEE14 of 83 percent. For each coat applied the MEE increase was greater for the white shellac than for the pigmented shellac. This greater increase in MEE with each successive finish coat for a nonpigmented versus pigmented finish was also observed with the gloss urethane varnish (finish 13) and the aluminum flake-pigmented varnish (finish 43). Increases in MEE for the paints (finishes 67 and 77) were similar to those for the pigmented varnish and shellac. Browne (4) has done an extensive study on the variations of MEE for a linseed oil paint according to the nature of the pigment. In general, pigmented finishes have much higher MEE than unpigmented finishes for any specific resin system.'

    As a last entry into the Forrest Products Laboratory Literature on this – and a bit more accessibly written – take a look at page 16-14 (Chapter 16 page 14) of their Wood handbook:

    https://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf"

    In the end we agree with Brian that B72 would likely be a more durable product and should lessen moisture sensitivity, although am not sure that it would be more effective that pigmented shellac. That is just not something I have seen compared.

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    I feel that there is no benefit to home washing cold pressed linseed oil to create a water white oil for making your own paint. The results are unlikely to be superior to a high quality alkali refined oil intended for hand grinding oil paint. This does not mean that you should not do it. Nor does it mean that if you do so your work will suffer. All drying oils yellow to some degree. Some take longer to get there but all will yellow. Purified oils do seem to yellow less, at least initially. High quality alkali refined oils are more pure than those refined at home.

    My understanding and general sentiment is that you are better off spending your time on the craft of painting rather than fussing with purifying your own oils. Some would say that the same could be said of making one’s own paint. This is partly true, as it is impossible to make a paint by hand that is as well dispersed and as lean as that made on large-scale roller mills. However, the ability to control which, if any, amendments are added and to make a paint with just the right feel can be very useful for some who really relish in the diverse rheological qualities of different pigments in oil binder(s).  It is also very interesting to experiment with fresh oil paint free of thixotropic thickeners, but this would be a waste of time for many painters who want a range of quality paint that all handle and dry in a similar manner.

    A good quality linseed oil for grinding, perhaps an oil of a lesser acidic number for mediums, stand oil, and perhaps a partially oxidized oil like homemade sun thickened oil for specific handling properties, should cover more than enough bases and be perfectly reliable (as long as rational painting practice is followed).

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    Honestly, I have not experimented with shellac to an extensive degree. It yellows and checks if used beyond the thinnest coating, especially if exposed to the action of air and light. Some painters in tempera have used water white shellac in extremely thin coats with no obvious ill results, but tests on the macro scale suggests that it is a poor “surface” coating. It would probably be fine for your purpose. Probably the 33% is a good place to start and after drying check to make sure that there is not too substantial a layer or, conversely, if it needs another application. If the first, sand it back and thin with more alcohol, if the second, apply an additional layer. Others may have more specific recipes for you.

    Having written this, I would suggest a different material for the purpose you mention. Paraloid B-72 dissolved in xylene (applied in outdoors or in a fume hood, etc) would do the same thing that you desire (a water free sizing/sealer)­­­­­, be composed of a material known to be very stable, and would be more sympathetic to and accepting of your subsequent application of water born acrylic dispersion medium. A Google search should provide you with an online source of this acrylic resin.  

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    No, stand oil probably would contain no foot. Even with other less pure oils, my experience with washing oils tells me that it is easy to fool yourself into thinking that you are removing substantial impurities even when this is not the case. Any actual foot can act as an emulsifier for the oil and water phases.

    Thicker oils readily emulsify in such conditions. I learned this the hard way when I tried to sun thicken oil above water in a single washing and thickening process. It worked fine for a while but if I shook the whole after the oil began to thicken, it was very difficult to separate the two phases. Even freezing was only partially successful and resulted in a large degree of loss. This is another reason why it is unwise to try to wash thickened oils like stand oil.


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    I have washed and bleached oils many times in the distant past but today I am not sure about the value of such a product. As to water washing, it does remove impurities from cold pressed or unrefined oils but the product is in no way superior to modern alkali refined oils. In fact, the resultant oil is very acidic. This may be fine for some purposes, like grinding oil paint, but there are alkali-refined oils available in a whole range of acidities. The best of these are going to be superior to anything that can be refined at home. This is covered more fully in this thread:

    https://www.artcons.udel.edu/mitra/forums/question?QID=355

    Sun bleaching is also less useful than it initially appears. You can certainly sun bleach oils to absolute water whiteness. The problem is that there is some color reversion over time. Take a sample of your bleached oil and keep it in a cabinet for a while and you can see this yourself.

    I can see no benefit to bleaching modern stand oil, which tends to be quite pale and is one of the most durable of the oily paint additives. I am refering to linseed oil heat thickened in a vacuum as oposed to archaic uses of that term.

    The one oil processing that does make some sense to me is sun thickening. The product of this is both partially oxidized and partially polymerized. It will behave very different from stand oil and will naturally dry much faster than raw oil or stand oil all without the addition of catalytic driers. This is not to say that it is superior to stand oil, just that it moves and dries very differently. Additionally, if the sun thickened oil is made with a quality oil (either alkali refined or sun thickened as you wish) it is a more appropriate paint additive than boiled oil or blown oil.

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    Factory-prepared stand oil is already highly refined, so I don't think "washing" would yield any improvement. I doubt any discernable "foot" would deposit as with unrefined oil.

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    ​Hi -

    All water-based acrylics contain surfactants and it is integral to their formulation. The same is largely true of water-based oils. Traditional watercolors do not have surfactants per se but they do have wetting agents - such as ox gall - that perform some of the same functions but are quite distinct chemically.  Regular oil paints at their most basic do not require surfactants or wetting agents, although many companies will use aluminum stearate which functions as both a dispersing and wetting agent, but its use is not universally embraced.

    In the end, surfactants are really mostly a term and class of chemical associated with water-based acrylics, and to a lesser extent, water-based oils.

    Hope that helps.

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    ​The short answer to this is: no.

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    Outside of the general concerns about animal glues, I would not recommend it to adhere a synthetic material. It does not stick well to these materials and its lack of gap filling makes it a poor choice in this instance. I would not recommend any contact cement. They are often very acidic any are really not meant for artwork. I think that the best results would probably be with a heat activated and stable adhesive like BEVA, although you may still have issues given the thin nature of the fabric.

    An acrylic gel medium is probably the best cold adhesive for this purpose. I understand the difficulty of stretching. How about trying something like this: Pre-stretch the fabric on a working stretcher large enough to allow you to place your panel within the back of the stretcher chassis. Apply the acrylic gel to the reverse of the stretched fabric (within the opening of the stretcher bars). Place your panel on the adhesive, face down. Weigh the back of the panel with books, etc. Let the panel dry a day or two and then cut the fabric from the stretcher bars and trip to size. If you try this let us know the results Also, others here may have additional thoughts or tips.

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    ​I would refer you to an earlier posting that is similar (you can link to this thread here).

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    In addition we have loads of information on this in our resources section in addition to helpful links listed at the end of each document. You should consult the sections on "oil paint" and "acrylic" in the Paint Mediums and Additives document which can be found here.

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    ​Well we have at least two lists in our resources section that might interest you: Artists' Treatises and Manuals and Technical Art History and Conservation Publications. While some updating is needed (a few very nice texts came out this past year) this will be a good place for you to start. It is really impossible for us to recommend any one in particular unless you get a bit more specific about what kind of information you are after....Merrifield and Eastlake are both valuable texts but I would not necessarily go to these if you are trying to reconstruct/reproduce Old Master painting techniques (but again it depends).

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    Thanks ​Matthew, my sentiments are the same. We have been on the road for the last week with litle internet access.

    Brian Baade

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    Other than absolute poverty, there is no reason to take the risk of using this canvas. 

    Brian Baade

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    It depends on the type of paint, thinners/mediums used, amount and frequency of exposure.​ Water-based paints like acrylics are generally very safe for artists of all ages. Tube oil paints themselves don't produce any harmful fumes, but some of the thinners used in oil painting can be harmful if used in large amounts, especially in an enclosed space without adequate ventilation, or with repeated exposure over a long period of time. The product package will give indications for safe use, and the manufacturer or retailer will be able to provide the SDS for more specific information about a particular product.

    If there is a specific art supply that concerns you, make sure to post a reply so we can point you in the direction of resources. Remember, however, that the Moderators are not physicians, so we can't interpret symptoms or give advice about a specific medical condition.

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    In my opinion, it's not worth the risk, especially if the picture never got past the initial ébauche. As a studio artist, I understand why you are considering it, but should you decide to proceed on the infested canvas, you wouldn't ever want to release the work for sale, and you'd have to worry about the spores causing future issues. Just photograph the sketch and use it to inspire another work on a clean canvas.

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    Thanks, and best wishes to all for a wonderful holiday season!​

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    ​Well we couldn't really do this without the amazing support from our funders and the excellent group of moderators who are willing to take the time to answer all questions, big and small. A Merry Christmas to you as well and to all of our participants and readers!

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    If your question refers to the ​consistency of paints straight from the tube or jar, there are a few reasons why some are relatively thin while others are stiff. Paint that has a relatively low proportion of solids to vehicle can be runny.

    Ideally, the solid ingredient in oil paint is mostly pigment, which gives paint its color. In craft-grade and scholastic-grade acrylic paints, some of the pigment might be replaced with an inert filler like chalk or, in the case of oil paints, waxy fillers that cause some of the oil vehicle to gel. There are also liquid acrylic colors (sometimes called 'fluid acrylics') that are specially formulated to have a thin body, with the same strong color as tube colors.

    Oil paints can also look runny if some vehicle separates out in storage. When the tube is opened, some oil might run out, but the remainder of the tube will have a normal consistency.

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    Thankfully we have loads of information on this in our resources section in addition to helpful links listed at the end of each document. You should consult the sections on "oil paint" and "acrylic" in the Paint Mediums and Additives document which can be found here.

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    ​I assume you are referring to the use of solvents and/or diluents here? Acrylic emulsion paints can be thinned typically using water while oil paints are GENERALLY thinned using a solvent (something like mineral spirits or turpentine). Is this the kind of information you are after?

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    ​We recently consulted Prof. Richard Wolbers at the University of Delaware about what may be causing the acrylic to stick in this case and he referred us to an article published in the Studies in Conservation Journal entitled "The influence of temperature and humidity on swelling and surfactant migration in acrylic emulsion paint films" by Ziraldo et al. (2016). Obviously many will not be able to access this article but to sum things up for you it is not really a question of indoor vs. outdoor evironments but really a question of what the temperature and humidity levels are in whatever environment your artwork is being stored or displayed. It tends to be the surfactant that collects on the surface of acrylic films and that can in turn give it the greasy hygroscopic nature that then causes the film to stick it to the glass. For acrylic dispersions that contain non-ionic surfactants one needs to avoid low temperatures (less than 30 deg C) and low RHs (less than 40%) as these surfactants will start to migrate out towards the surface in these conditions. As to what solvent you can use....honestly this is a complex question. You might be better off consulting with a trained conservator on this one as it will definitely require a bit of testing and access to several solvents and/or cleaning formulations that you are not able to readily obtain. Hopefully someone may be able to weigh in with some good suggestions for you beyond the "take it to a conservator" one.

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    Hi, All. I'd like to make sure we are working from correct product information for Dura-Lar. I don't believe it is a "hybrid" film, co-polymer or laminate; I think it is just polyester. ​From the vendor's site: "Dura-Lar is a polyester based film known for its clarity and stability. It has a high heat tolerance, will not tear or discolor and is archival. Acetate is a general purpose film that is biodegradable, tears easily, does not have a high heat tolerance and is NOT acid free or archival."I believe elsewhere on the site, the vendor claims that Dura-Lar "combines the best of Mylar and Acetate" but I think that is just marketing language intended to persuade artists that the newer product offers the advantages of acetate, not that it is somehow partly acetate.

    Also, I believe in this case the Dura-Lar film is the painting support, not a framing material, and the artist is asking about deposits on the clear passages of the film. It had occurred to me that the Primal AC35 application may not have adhered well to the film, and was possibly responsible for the "greasy" residue.

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    Our expert on preservation framing and preventive conservation has asked for some clarification and provided a provisional answer. I have copied his response below.

    There are a number of issues, here and much on which I am not sure of. Looking at Duralar, on line, I discover that it is some amalgam of acetate and polyester, whether it is a laminate or co-polymer, I can’t say, and I always thought of polyester by itself, but from what I see on line, I was wrong. It seems that Duralar is used to protect printed paper, but I have no idea as to how it might have been adhered. Now to answer the question

    If moisture and “greasy” accretions are found on an acrylic painting that has come from a frame, it is likely that the moisture has come from the mechanics of the frame, namely, the possibility that the glass trapped moisture coming from the wall, but the esource of anything that feels greasy, is harder to pin point. Framing can produce salt on glass and various acids, but oils are most often found when oily plasticizers come from plastics. Among the materials mentioned, in the question, there are three plastics, acrylic, polyester, and acetate. The first, in the paint, and the latter two, in the Duralar and among these, it is probable that the acetate may be the source. As to removal of the Durlar, from the painting, one would need to know how it was affixed, and without a complete understanding of that, leaving it in place is safest, for now. The moisture should evaporate and the greasy accretion may be reduced, with minimal water and a mild detergent. The interior of the frame should be cleaned the same way and everything should be carefully watched, since acrylic paint can soften and cling to glazing sheets, in damp and warm settings. 

    Hugh Phibbs

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    This is outside of my knowledge base so I have forwarded the question to a few individuals who are more familiar with acrylic films and issues associated with framing.

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    You could certainly make tests of your powdered stone and perhaps you could find a use for it. I have doubts about is appropriateness for silverpoint. I generally use ground silica for that purpose. The hardness of silica facilitates mark making. Perhaps yours would be too soft. Who knows unless you try.  On the other hand. Marble dust, ground gypsum, and ground silica are about the cheapest materials used in art making. You have to decide for yourself if it is worth it to you to substitute your ground stone powers for materials of known qualities and a history of successful application.

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    I also have no experience with the Zecchi product or its formulation so I can't comment about it efficacy.

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    If I understand the question correctly, it seems to me that secco painting, as compared to buon fresco, is always applied on a wall that has dried and preferably cured. Therefore, the pH sensitivity of the pigments is less critical than with true fresco (where they are applied into a wet wall of calcium hydroxide which converts to calcium carbonate in the presence of carbon dioxide). Secco paints only need to withstand the pH of their binder and any residual pH of the carbonated lime. The wall would be chemically the same as limestone. As to the suitability of acrylic, it would seem fine. The only issue could be if the acrylic component is high enough this could result in a pronounce sheen. This is really true of almost all secco techniques as compared to buon fresco. Casein and distemper are probably the best in terms of this issue. The continued solubility of animal glue makes distemper a poor substitute in terms of longevity.

    Apologies if I misunderstood your question.

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    Matthew is probably right about the particle size issue

    The comment below was written by Bruner Barrie who runs Sculpture House

    Since there is various type of soapstone or Talc Block that may also be called Serpentine or know by other names it would be difficult to answer this question without more information.  I cannot see why any of the different types might not be used with Gesso although the porosity might be different within the different types. Montana, India African, and Alaskan stones all vary so I would suggest the person take a small amount and mix up test batches and lay around to see what they might like best. That is what I do quite often when trying something new and exciting and it seems to work well in the long run.

    Hope this helps.

    Thanks and Sincerely,

    Bruner

     

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    Traditional burnished gold could only be accomplished with water gilding. This means that it needed to be applied over an animal glue containing ground and usually over an animal glue containing colored bole. This means that the ground must be true animal glue containing gesso or animal glue-chalk. I understand that there are other methods that achieve mirror-like gold effects. Kölner Insta-Clay is one such product. I have never used it so I cannot comment on its efficacy.

    The reason why you cannot burnish oil gilding is that you are actually burnishing the ground and bole, not the gold.

    When oil gilding or polymer gilding it is usually best to apply some sort of sealer to cut the absorbency. This prevents having the gilding fail where too much of the size was absorbed into the object. I know that shellac was often used for this purpose but I would assume that any was approved for permanent work, dried insoluble, and could be applied smoothly and without brushstrokes would work well. Having it in a spray can would be helpful as well.

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    It is not that PVA size in inadequate, it is that one coat is not adequate. Multiple coats should work fine. Acrylic dispersion just seem to accomplish this with fewer coats.

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    Matthew, the same thing can be seen on paintings hung on exterior walls (those that have the outdoors on the other side as compared with interior walls). The movement of moisture through the wall has a major impact on preservation. I have images of a pair of pendant portraits from the 19th century that were painted at the same time and with the exact same materials and techniques. The one hung on the interior wall is in very good condition while the one hung on the exterior wall is flaking and in a poor state of preservation. 

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    Art is only as durable as the collector's commitment to proper display and care. A watercolor needs to be correctly framed and displayed in a location that doesn't excessively expose colors to UV light. The same is true of any painting. Gallery owners have told me horror stories about valuable, important works hung in client bathrooms, over fireplaces or even on outdoor patios. Of course, the artist can't claim, "warranty void if hung in the bathroom".

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    ​Soapstone dust is not a good substitute for calcium carbonate in paints and grounds. The particle size of the dust produced by carving is probably not optimal for paint and grounds anyway. I would just dispose of it (wearing a particle filter mask), and if you want to use hydrated magnesium silicate/talc in the studio for inks or ceramics, select a cosmetic grade that is finely processed and product free of asbestiform particles.

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    Let me first say that watercolors can be a very permanent medium, especially if they are created and treated in the manner that you suggest. I would bet that this is not the norm. One could also say that most oil paintings are not created and treated in an optimal manner, as well.

    There are reasons why many commentators seemed to elevate oil paintings above watercolors in terms of longevity. The first is due to the nature of the paint. Historically, watercolor manufacturers were more likely to include more fugitive pigments in their watercolor line than their oil lines of paintThis was backwards thinking on the part of the art materials manufacturers. The gum Arabic binder in watercolors is very minimal and does not really surround and coat the pigments in the same way that oil or acrylic dispersion binders do. This means that the pigments receive the full force of visible and UV light. Pigments that are barely suitable in oil are outright fugitive in watercolor. The other binders are more fully covering and absorb some of that energy. The presence of a varnish creates even more of a barrier. You did address this and included only permanent pigments in your ideal description.

    The paper is another source of sensitivity in watercolors, even the highest grade cotton rag paper can suffer photochemical degradation. Again, you mention the use of UV blocking glass, which would prevent this. Canvas is usually made from cellulose as well, but in traditional painting, this is covered with a ground and the paint, blocking this radiation.

    Finally, the absorbent nature of a watercolor painting means that dust is easily trapped in its surface and the water-soluble nature of the medium complicates cleaning. And again, your ideal watercolor addresses this.  So if the one takes the precautions you describe, watercolor can be very permanent.

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    ​Hi -

    If deciding to paint on metal with acrylics the most common choice would be aluminum in order to avoid the problems associated with more corrosive options, like steel or copper. Along those lines, the best introduction to the topic would be an article Mark Golden wrote for our Just Paint newsletter:

    http://www.justpaint.org/painting-on-metal-an-introduction/

    as well as this one on preparing Dibond, an aluminum composite panel:

    http://www.justpaint.org/painting-on-dibond/

    Especially if going outdoors, and/or choosing to work on raw aluminum, you are best off preparing the metal with high end commercial primers made for that material. As the article lays out, for aluminum the best options will involve three steps of degreasing, etching, and then application of a conversion coating. Because this involves a lot of work, we strongly recommend going with a pre-prepared aluminum panel such as Dibond, which comes with multiple surface coatings - including clear coats that preserve the look of brushed raw aluminum - which will allow you to paint on top of them will far less prep. In fact you could get away with simply scuffing the surface, cleaning with isopropyl alcohol, then using an acrylic gesso if painting indoors or using something like Sherwin Williams' DTM Bonding Primer or XIM's UMA. Both mentioned in the articles above. After that, then you can proceed with acrylic paints as you would normally. If going outdoors, you would need to be more selective about which colors you use. Here is a list we give for outdoor murals which are the most durable and lightfast in exterior conditions:

    http://www.goldenpaints.com/technicalinfo_murals#goldenSuggestedColorList

    While the list is based on testing of our own paints, in general the recommendations should hold for most other brands as well.

    Once done, then you should protect the piece with a removable varnish or topcoat. If going outdoors, the gold standard would be a two-part automotive urethane, which an auto body shop can apply. If that is not an option, then a solution acrylic varnish - such as our MSA Varnish or our Hard MSA Topcoat - would be alternatives. Liquitex's Soluvar would be a similar choice. However, none of these are as physically durable or chemically resistant as the auto clear coat. If the piece is indoors, then your options are broader and even a water based acrylic varnish would be a viable option.

    We hpe this is helpful. In truth a lot depends on the particulars of the piece - whether indoors or out, - and your expectations about longevity. If the piece only needs to last a decade or two, that is different than wanting something that is permanent. Even the best metal sculptures outdoors - including a lot of Calders - end up being regularly repainted because the environment is just so challenging. But indoors your chances for the initial coatings lasting a long time are much better.

    If you are planning to use a different type of metal, or having further questions, let us know.

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    ​Yes I think that is probably correct...at the moment there seems to be little known regarding a) the precise characterization and b) quantity of additive(s) being used in this particular brand of "oil paper" to render it suitable for oil painting. I will send an additional query to the scientific community to see if there is an off chance that someone has analyzed one of these papers but as they are fairly new to the market I am not hopeful on this matter. I can comment however on your musings re: Jan van Eyck. While A. P. Laurie's writings are indeed valuable and interesting to read, unfortunately I would not place a whole lot of faith in his conclusions regarding Old Master painting practices. We address this issue in our resources section in a document called "Myths, FAQs, and Common Misconceptions" (particularly in No. 8 and 9). Today we do know lots more about Jan van Eyck and Flemish painting technique and there is little evidence to suggest that there was a systematic use of distemper (glue-based) or tempera (egg-based) underpainting to prepared panels before applying oil (actually "gesso" would be an incorrect term here as that specifically refers to the use of calcium sulphate or gypsum....the Northern European painters at that time used chalk and glue for their grounds). But I do understand your point in including this specific reference as it relates somewhat to the topic of the thread. What appears to be a typical Flemish technique is to first apply an ink underdrawing over top of the chalk-glue ground (which MAY have had additional layers of glue applied on top of the ground to cut the absorbency). This was usually then folllowed by a pigmented oil-containing layer (which the Italians would later call an "imprimitura" layer). We do know of a few instances where a layer of unpigmented oil was applied either over the chalk ground before the underdrawing OR more commonly over the underdrawing. This was then usually followed by layers of oil paint. Researchers have reported a handful of cases where egg tempera was used as a full underpainting before oil colors were used to cover the entire surface. However, much of this research was done quite early on (even though it was performed WELL after Laurie's time) and even these results should probably be re-assessed. 

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    Really, there are no good reasons to use common cardboard. Acid Free blue board is vastly preferable for the reason enumerated above. I have a query into another moderator for more info about your question posed on the other thread.

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    ​Hi - We do not know what is in the Zecchi product and would encourage you to communique with them directly to understand what their thoughts are about the suitability of their paints for buon fresco. I can say that in general acrylic binders are quite resistant to alkaline surfaces and materials. In fact acrylics are often included in plaster recipes to increase chip resistance - such as our own Acrylic Modifier for Plaster. But it is also important to know that the acrylic binder does not on its own protect pigments that might be alkaline sensitive - so pigment selection remains critical.

    On that front, traditionally all organic pigments, including synthetic ones, would be avoided. However we are also unaware of any rigorous testing that directly shows if this is true for all organics, without exception - including the Quinacridones, which are often listed as alkaline resistant by the manufacturers. The real question might be just how resistant are they, since fresh lime plaster would an extreme case. In this regard, the RealWorldColor is interesting since the author's own testing appears to show the Quinacridones as stable for fresco. If wanting to be more adventuresome, and willing to do additional testing on your end, you can certainly evaluate the palette given here:

    http://realcolorwheel.com/fresco3colorchart.htm

    Just keep in mind this comes with no guarantees that your own experience would be the same, so do as many trials as you can.

    Obviously the safest method is to stick mainly with a truly traditional, well-proven list of colors, such as this one:

    http://www.noteaccess.com/MATERIALS/FPigments.htm

    This can be safely supplemented with any other iron oxide pigments.

    Hope that helps.

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    The nice thing about using solvent borne acrylic as a size is that it does not cause unstretched paper to buckle like acrylic dispersion sizes can.

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    Also I have been thinking about what would be the best replacement for hide glue and am becoming convinced that solvent acrylic is best, since it lacks evaporation holes and I use it, when I am working on paper with oil. Another question that comes to mind is what goes under the paper. Artists working in oil tend to not want to use mats, glazing, and/or mounting to Dibond and I often wonder why. Hard mounting, before the painting is done can be done with acrylic gloss medium, but how to do this, when the painting is done, should include some release layer and that is what I am working on these days. As I said, before, I think acrylic is more flexible and clear than either PVA or even EVA and I have found it to be a glue that will even bond to the surface of an oil painting. I am thinking of polyester felt or Volara as a release material and will let you know how my testing works out, but I see this as an issue that will continue to come up.

    Hugh Phibbs

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    Paper is a wonderful substrate for art and watercolor paper has cotton and animal glue to protect the cotton fibers, but that glue is not enough to keep oil media from staining and oxidizing, over time. I first heard that Arches was making an oil paper, when I was teaching in Paris, but I have not been able to learn what is added to the paper to block the oil. Their literature stresses the idea that the paint will have some grip on the surface, avoiding the “crawl” one sees, when oils are applied so some slick surfaces, but the penetration of the oil must be limited. I have worked on Arches cold pressed, applying acrylic, in varying thicknesses, over which I then applied oil, and my experience showed me that a stain of acrylic did not prevent oil penetration and that a film of acrylic was needed to get to a point that oil did not show up on the verso. Acrylic medium can be applied to watercolor paper, to prepare it for oil and one can assess the thickness needed by looking for oil penetration. Acrylic should be more flexible and clearer than PVA, but with any aqueous dispersion, that product should be applied, allowed to dry, for two weeks, and then the dry film should be washed with water, to remove the surfactant that has leached to the surface. If tooth is desired, a matte acrylic and be used and the paper can be wetted, or a wetting agent (ox gall or alcohol) can be employed, but they would complicate the chemistry. 

    Hugh Phibbs

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    ​Hi there!  I'm curious, when you say "sizing" what process are you using?  Sizing can refer to a few different processes, and I want to make sure I understand how you are working. 

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    ​Yes this is true (that graphite does NOT migrate through egg tempera films). Again I suspect that this notion has been propagated by the occasional scenario of the paint layers becoming more transparent over time thereby making it SEEM as if the underdrawing doen in graphite is "migrating" up through the paint layers (when in fact it is simply becoming slightly more visible). While this tends to happen more readily in oil paint films it certainly can happen to a certain extent with egg tempera depending on many things (the particular pigment(s) present, the thickness of the paint layer, etc.).

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    Brian, We've been tripping over each other lately! I'm glad if I added something useful.

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    ​Ha

    Matthew, you posted while I was editing my post. Anyway, multiple voices are always better. Thanks for the commentary on the health issues. I had completely missed that in my response.

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    Hi

    The medium you describe was used by many, many painters in the 20th century and is identical to the medium Ralph Mayer suggested for glazing in oils (although his recommendation contained cobalt drier as well). Today this medium is not considered as benevolent as it was in the past. The large percentage of soft dammar resin can contribute to a paint film that is sensitive to the solvents used to remove degraded varnish in the future. It also contributes a degree of brittleness to the paint. Stable paintings can be made using such a medium but it would need to be added in very small proportions as compared to the oil paint. In practice, this is unlikely and it is best to avoid mediums that contain soft resins. Finally, the dammar is the reason why you have required turpentine rather than a less noxious solvent like a highly refined zero-aromatic odorless mineral spirits. Dammar is not soluble in these solvents and requires either turpentine or a mixture with a high proportion of aromatic hydrocarbons.

    There are some other alternative solvents but they tend to smell just as noxious during longer painting sessions. Some of the claims of lower toxicity for some of these may actually simply be the result that they have not been tested as extensively as the more common diluents.

    So, what you need is an oil medium that does not require turpentine (or aromatic hydrocarbons) or soft resin.  Stand oil diluted with a solvent is perfectly fine in terms of stability. It may be less desirable in terms of paint handling. It really depends on what you are after. I have found that this mixture really levels paint strokes and can contribute a greasy effect rather quickly. It is sticky without having the “feel” that your old medium had due to the resin. Linseed oil and solvent is workable as well although its “feel” is also very different from what you are used to.

    I personally have not liked the handling of gelled alkyd mediums but others really love them. I have found that the fluid alkyd mediums more closely resemble the older mediums like the one you describe. You may want to thin them with additional OMS if you use larger amounts of medium as you suggest. You could even use one of these as a component of a three-part medium by substituting the alkyd for the damar and OMS for the turpentine. Finally, have you tried using any of the newer solvent free oil mediums? A Google search should yield a number of these offered by different manufacturers.

    Sorry if this is a less than satisfactory answer. Perhaps others here have a different or additional take on this issue.

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    There are health risks associated with exposure to Pure Gum Spirits of Turpentine, including respiratory problems and allergy-like sensitivity. Many experienced painters with a long history of turpentine use have migrated to clean Odorless Mineral Spirits. This type of solvent is not completely without risk, but OMS does not induce materials sensitivity. OMS also evaporates at a slower rate than turpentine, so the buildup of vapor is not as rapid. Even high quality art supply brands of OMS are very economical. Of course, this is still not solvent-free painting. Also, the paint doesn't behave quite the same with OMS compared to turpentine.

    Damar varnish also contains turpentine, so you may want to consider replacing that component of the medium with walnut alkyd medium or solvent-free alkyd gel. These do cost more than damar (especially homemade varnish) but they do offer very nice handling and drying properties without hydrocarbon solvents.

    Another reason to consider replacing damar in your studio is that a paint film containing significant amounts of damar can remain soluble for a long time, making cleaning more problematic. Since you mention that you use large volumes of medium, solubility and other drawbacks of damar (e.g. darkening, embrittlement) may be a concern.

    The vegetable oil components of your medium don't generally present any particular health risk. Linseed, stand, safflower, poppy and walnut oil are all free of hazardous vapors, though some do find the smell of linseed oil unpleasant. All drying oils (including cooking oils) can spontaneously combust from buildup of heat from oxidation, when oil-soaked rags are left balled up. Rags can be left flat to dry before disposal, or immersed in water in a lidded metal can.

    Finally, when solvents are present in the studio, adequate ventilation is essential- there's no substitute. Make sure air is moved and replaced, not just moved around with a fan.

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    My thoughts are simply that such canvases are unsuitable for anything other than the most disposable sketches. The problem with this is that you never know when an expected humble sketch turns out to be very successful. It would be far better to buy some better quality stretcher bars and a length of primed substantial canvas (rather than the overly thin cotton canvas usually encountered with general pre-stretched, primed canvases). With these you can create your own canvases. That way you can always easily remove and dispose of unsatisfactory paintings and have a quality product if you are pleased with the result. You could also simply purchase higher quality pre-stretched/primed canvas by a reputable canvas supplier.

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    ​I happily stand corrected :) One of our moderators Dr. Greg Smith has identified a resource that does indeed possess such images. He is looking into scanning the photos for you...but in the meantime you can try to locate the reference yourself should he prove unsuccessful: Burnstock et al "A pilot application of SEM and hi resolution x-radiography for the conservation of paintings" in Historical technology, materials, and conservation: SEM and Microanalysis 2012.
    This was the conference held at the British Museum, and the proceedings were published by Archetype.

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    ​Very intriguing question for sure :) So first of all I am assuming you are after VERY particular SEM images. Just so other readers have a bit of background, SEM-EDS can be used to generate two types of images....one that can show the distribution of certain elements across the surface of a sample and another that can show the morphology/topography and, in some cases, the general composition of a sample. I am assuming that you are after the latter. With paint samples I am afraid this is a bit of a problem as most of the time paint samples are mounted in a specific manner that involves encasing them in a polyester-based resin (or another type of hard resin that can cure in 24-48 hours). The resin is MEANT to penetrate all of the interstices of the sample to provide a smooth even surface when the paint sample is polished down and to secure the paint in place (SEM-EDS is performed under a vacuum and it would be a sad day if the sample were to get sucked up into the instrument....that would cause damage that can get rather costly). So you would need to find SEM images of paint swatches that have somehow been glued down or afixed to a surface...and then the images would have to be collected in secondary mode of the exposed surface. To be honest I do not think this has been done. But what I can do is put a query out there to the conservation science world to see if I am wrong about that.

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    Hi again -

    Please link to my reply and share with the Facebook group you found this discussion as I would not want the misinterpretation to stand without comment there as well.

    Thanks.

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    ​Hi -  

    My first and most immediate response was "whoa whoa - where you are getting that interpretation!". First, nowhere in the article do we mention Gamblin, and that is important as we do that on purpose and on principle as we would never directly comment on another manufacturer's products, especially in a way that might be construed negatively. When we use products from other companies we do so with an eye to simply understanding how they work with our own products, as we assume that people will mix and match out in the world and its important for us to be aware of those things. But we do not mean those tests to be evaluations of the products used within that manufacturer's own product line. We are not set up and it would be anathema to us to present our testing as a form of third-party consumer product testing for the industry. Finally, we also have great respect for Gamblin and have had a long relationship with Bob and would never imply that they made anything other than professional products.

    Second, here was our summary about PVA Size up near the start of the article:

    "PolyVinyl Acetate (PVA)

    While pH-neutral PVA adhesives have long been used in conservation and the book arts, some manufacturers now provide PVA-based sizes for use in preparing canvases. These should adequately protect fibers from the oxidizing effect of drying oils and prevent strikethrough. In our own testing, the number of required coats to achieve this was varied, with one coat clearly sufficient for a faster drying, alkyd-based ground we tested, while a minimum of two coats were required for all the slower drying, oil-based products. Always consult with the manufacturer and check for your own application to see what is optimal."

    Nowhere do we imply that a PVA Size is not a suitable and viable system. What we did find was that if paired with a fast drying alkyd-based ground, one coat was sufficient and worked well. It was with slower drying very traditionally formulated grounds, such as our own Titanium or Lead Oil Ground, where we saw strikethrough as the oil had days to be able to work its way down and through - and oil molecules are rascally things that are great at penetration, especially if given the time. A faster drying alkyd ground, on the other hand, sets up rapidly - often overnight - and so there is less chance of that happening. And even in the above case, applying 2 coats of the PVA size reduced strikethrough to a very minimal level, and I could easily imagine a 3rd coat would have taken care of that. But the main thing to keep in mind is that when pairing products, especially if choosing a size from one manufacturer and a ground from another, you need to do some testing to see what works as directions are almost always assuming the best process for use within a manufacturer's own system. So by all means pick and choose and combine, but when doing so you should assume that some adjustments to the instructions might be needed.

    Ultimately PVA Size is a well tested option that has a lot of use and acceptance in conservation circles and we think it is a perfectly fine option. The one we tested was quite flexible, especially if comparing to the absolute gold-standard for stiffening, rabbit skin glue, which is what we aim for duplicating when developing an option using our acrylic sizes. I am not sure, to be honest, if a PVA could be made stiffer, but I would not avoid using PVA Size on that basis alone if it is something you like using. It did leave the canvas feeling very supple - almost like it had no coating - and that has a certain allure.

    In the end I think you can feel that the Gamblin product is a professional one and I would not in the least disparage the company or feel that they in any way misrepresented it. They have had a long relationship with folks at the National Gallery - we share in the same contacts - and the Canadian Conservation Institute has done some of the most extensive testing of PVA Sizes around. They literally 'wrote the book' on the subject:

    https://www.iiconservation.org/node/877

    http://www.tandfonline.com/doi/abs/10.1179/2047058414Y.0000000129?scroll=top&needAccess=true&journalCode=ysic20

    https://pub.cci-icc.gc.ca/resources-ressources/publications/category-categorie-eng.aspx?id=20&thispubid=533

    and I would have no doubt that they reached out or worked with folks there when developing their product.

    Hope that helps give you some confidence. Pairing a size and ground and getting a system that is right for you can take some fiddling and testing. And never hesitate to reach out to Gamblin directly if you need assistance or have questions with their products. They should be very helpful based on my own interactions with them. And if you have questions about something we wrote - and in this case something I did - please reach out to us directly if needing clarification as well. We are always happy to do what we can.

    Thanks.

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    I have very little to add here other than to mention that in addition to the difference already mentioned, quinacridone red is also a little less transparent and, therefore, lighter in mass tone than either alizarin or rose madder lake. As stated, though, these small differences should not stop one from using the vastly more permanent alternative for anything other than a historical reconstruction.

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    Hi Bob -

    As you might imagine this topic can have many layers of complexity so will try to address some of the basic issues. I also have never done testing on NR9 - it is not a pigment we use - but can share results from Alizarin Crimson which is generally seen as the weaker between the two. As you intuited the lightfastness for all these colors would be worse in the tint and in fact lightfastness ratings are based on the performance of a specific tint let down with titanium white until you achieve 40% reflectance in the wavelength of maximum absorbency. For a sense of what that looks like, and a description of the lightfastness test procedures, see the following article:

    http://www.justpaint.org/alizarin-crimson-now-you-see-it/

    and for how to interpret those results based on what is called delta E, see:

    http://www.justpaint.org/delta-e/

    Many but by no means all lightfastness II and III colors can perform markedly better in the masstone. A classic example would be Alizarin Crimson, and by extension NR9 as well. See the following where we show some actual results:

    http://www.justpaint.org/alizarin-crimson-now-you-see-it/

    As you can see the deeper masstone in the oils holds up quite well - it actually barely budges and on its own would be considered  a strong LF I. But as a tint there is a major bleaching out. Fanchon Red is similar in this way, but not so much with PY 3, where masstone and tint scored very close to a LF II.

    I should also point out in the Alizarin Crimson piece you can see how effective a UV protective Varnish was in preserving what would otherwise be a light watercolor wash. Or see the results of applying a varnish to fugitive dye-based inkjet prints towards the end on the piece on Lightfastness. That said, applying a UV varnish or UV filtering Museum Plexi or Glass, does not always work that effectively. If a pigment is sensitive to light within the visual spectrum then the varnish and glass with have far less impact.

    In truth, outside of historical interest, there really are few reasons not to seek out more permanent alternatives that would be safer to use. For example, Pyrrole Reds are rock solid and can replace napthols, while Bismuth Vanadate lines up fairly well against PY3, and finally PR177 is much more permanent that either PR83 or NPR9, but is not a perfect match being a bit cleaner and higher Chroma. However, if wanting to use them, keep them as close to full strength as possible and applied generously, and if aesthetics and finances allow, use a UV protective spray or UV Plexi at the end.

    Hope this at least answers some questions.

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    ​Hi Ron -

    You'll be fine.....always a pleasure to chime in.

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    This is always one of those difficult questions to answer. As you gather from your own experience the risks are very minimal and usually nothing happens, and because of that, I don't want to raise incredible concerns. The odds of a problem occurring are probably very low. But.... (stalling as I put on my technical hat).......can I imagine scenarios where something occurs? Sure. Higher humidity could slow the evaporation of moisture enough that the oil paint does not penetrate as deeply, and so develops less mechanical adhesion. But I think it would need to be extreme to really be a major issue. Also, keep in mind that acrylics are alkaline in their wet state - and contain a small amount of ammonia - so until the majority of the moisture has evaporated the canvas surface could still be alkaline as well. Alkalinity, in turn, can cause the fatty acids in the oil to saponify, which could also impact adhesion. Because it is just good advice to keep ammonia and oil paint away from each other, we generally prefer giving the surface extra time to fully dry and be truly pH neutral.

    That said, we have never seen the above issues come up in our testing, nor in all the years we have fielded calls and inspected canvases. So my guess is that it is extremely rare and requires something of a perfect storm. But......tech hat again......perfect storms DO happen, and if it happens on a really important piece, that can be heartbreaking.

    In the end, the 24-48 hrs. you are waiting is shorter than the 3 days we recommend as a minimum, but we are also erring on the side of caution and trying to give advice for people living in a lot of different environments. Also a brushed on acrylic layer is just so thin that in truth the majority of the moisture will easily be gone in that initial timeframe. At the very minimum, however, I would say do not paint on any water-based coating if the surface still feels cool or clammy, as that would clearly indicate a good deal of evaporation is still taking place. And as I always like to note, if you can prepare several canvases at once, then even if you use one after a day or two, the others almost invariably will sit around for a week or two.  

    Hope the above is helpful. In the end it is all a matter of risk management. If you always gravitate and want to adhere to the absolute best practice, and have minimal to no risk, wait two weeks. If a small amount of risk is tolerable, wait 3 days. If you feel okay pushing that envelope slightly, then your 24-48hrs is likely fine. It reminds me a bit of the quandary whenever reading medical statistics. If doing something increases the likelihood of an illness by 400% that sounds shocking, and one quickly promises to amend their evil ways, but if that translates to actual incidences going from 1% to 4% that might seem okay for the tradeoff, and french fries it is!

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    Matthew, no problem, more responses are always better that fewer. We tend to focus on different aspects of the concept and the combination of replies is always richer than would be the case if only one person responded.

    To the OP

    Drawing into thicker paint should insure integration and be stable. Additionally, even if you do not follow this precaution, your work may still remain relatively stable. Drawing into more substantial layers of oil only ensure this.

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    Sorry, Brian, I must have been writing while you clicked "post". ​

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    Once a graphite sketch on the ground is integrated into a dry paint film it should be stable, unless the graphite application is so heavy some unbound, loose particles remain. If graphite lines are in the top layers, , the varnish can mix with the graphite particles, and consequently these marks can be lost if the varnish is removed.

    Graphite particles don't migrate through a dry oil paint film, but the material is denser than charcoal and can mix readily with paint, staining light colors in the first application. Also, as paint ages and becomes increasingly transparent, marks underneath may become more visible.

    We know graphite doesn't migrate within a paint film because Albert Bierstadt used a graphite-based oil ground for many of his paintings and, while the pictures may have darkened slightly, the ground color has not asserted itself through the actual paint. Unfortunately graphite primer proved not to provide a very good surface for oil paint adhesion, and Bierstadt eventually switched back to lead white grounds.​

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    Like so many things that come up on this forum, it depends on a number of factors and just what you mean by durable. Graphite in itself is very stable so that is not an issue. Probably the biggest factor here is just how much oil paint are you drawing into. If the paint is substantial enough that the drying oil saturates the graphite particles, the graphite would be incorporated into the paint and would be quite stable.

    If the particles are not incorporated into the paint, the particles would rely more on mechanical adhesion. This is itself is not a deal breaker. There are many, many paintings where contours have been reinforced with pencil. The only real problem is possible smearing on one hand or removal during future cleanings on the other. You mention that the work will be varnished, this means that the first potential issue would not be a problem. However, the graphite could possible be displaced when and if the varnish is removed at a later time. This is in no way a certainty. Pencil was sometimes used to depict the rigging on maritime paintings. I have observed some examples where the graphite lines have resisted restoration and others where the rigging is partially removed. To be fair, though, I have also seen plenty of instances where rigging executed in oil paint  (or oil with an addition of varnish) has been removed by the insensitive cleaning of an ill-trained restorer.  

    I hate to keep giving less that definite answers, but “it depends” is often the only true answer.

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    ​Leslie is an amazing force unto herself and is a major reason why I transitioned from fine art to technical art history and eventually art conservation. In fact, it was my purchase of her "unpublished" doctoral thesis in 1999 that solidified my decision to enter the conservation field.

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    ​Probably the best way to answer this is to introduce you to AATA. Do a search for Leslie Carlyle. http://aata.getty.edu/Home

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    Thanks all.

    As an interesting connection to this dialog, I actually spent a summer working with Leslie Carlyle on her HART project in Amsterdam (2005) hand grinding, using a granite muller and slab, hundreds of lead white paints with additives/other pigments added in 5% incriments (barium sulfate, etc) in various mixtures of oils in 5% stepwise additions (eg, cold-pressed linseed oil 95% 5% poppy oil, 90% CP L Oil 10% poppy oil, and so forth). We took these to a few research facilities and paint manufacturers to measure rheology. The last couple of days were spent painting out all of these on multiple substrates. Leslie has used these, and many others, for her years of subsequent research.

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    I agree with both Brian's and George's assessment. It is also important to mention that various form of refining (including less industrial versions of both acid and alkali processes)  were carried out in the past 

    (see the section on Refining linseed oil paints starting on pg 14 of Analytical Chemical Studies on Traditional Linseed Oil Paints 

    https://pure.uva.nl/ws/files/3716376/20662_Thesis.pdf

    and that what passes as 'cold pressed' both historically and today is not a singular standardized product. While starting out as a raw expeller pressed oil - without the use of heat or chemicals - it ultimately undergoes any number of refining processes that historically changed over time and had wide regional variation. So that would complicate any claim or study as you would need to define what you are comparing to. Also remember that even the genetic make-up of flax had changed over time and it is not at all clear that the fatty acid profiles of todays' oils match that of the past, since strains have been continually optimized and crossbred to have better resistance to disease, draught, yield, etc.

    That said, we continue to study this area and are open to the possibility that older processes of refinement might produce some interesting differences in handling and drytime, as Leslie Carlyle's work on the historical reconstructions of lead white using differently processed oils seems to point to. But currently we have not seen any evidence that structurally cold pressed linseed oils are superior and indeed the alkali-refined oils we use seem more consistent and less variable in its batch to batch qualities.

    Hope that helps. 

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    ​I have been scouring literature on the differences between non-refined (cold-pressed) and refined oils for many years, and have not found any that informatin that would support claims attributing improved mechanical strength of paint films due to the refinement of the oil. What is well-known is that refined oils contain less impurities so that they tend to yellow less and dry faster. However, this subject has not been studied, so there is no definitive answer.

    As has been found in studies by Marion Mecklenburg and others, is that the mechanical strength of paint films is largely due to the pigment, such as lead white. Whether the state of refinement has any effect on this is not clear. However, understanding the nature of the impurities in oils makes its unlikely that they would contribute positively to the mech8ca strength of the dried paint film.

    In one study we conducted, however, we found a difference in the tensile strength between types of oils, such as walnut and linseed oil—linseed oil exhibiting higher tensile strength than walnut oil.

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    I am not a commercial paint maker, but this is of interest to me. The bias that you mention has been around for quite a while. The idea is that while the alkali process removes more organic impurities, it may leave some residues or somehow weaken the oil in a deleterious way.  Some would suggest that the refinement weakens the oil in some manner creating a product that is lighter and less prone to yellowing, but not as capable of adequately binding a given volume of pigment. We first have to ask, how could an oil that contains more impurities be superior? However, this was certainly true very early on when oils were crudely refined leaving residual acidic or alkaline components. This was compounded by the fact that the oils that were generally refined by these processes were those of the coarsest extraction and were intended for only the crudest uses. This is in no way the state of things today.

     Linseed oil refinement is a carefully controlled process, which allows for cleaner and purer oils than available previously.  We do have evidence that modern quality refined oils yellow less than cold pressed oils. In the recent past, the only real benefit to cold pressed linseed oil was its use in grinding oil colors (as opposed to use in mediums/commercial oil varnishes for wood, etc. where this was less valuable) due to its high acid number. While this does contribute a bit to yellowing, it does allow for the creation of a paint that requires substantially less oil than paint made with linseed oils of lower acid numbers. This is a non-issue today since alkali refined linseed oils are available in any acid number that is required. Additionally, If you read mid-20th century literature on the subject you get the impression that oil paints made from non-cold-pressed oils were more likely to exhibit a suede effect. I am firmly of the opinion that this effect was the result of the commercial use of stabilizers, like wax, aluminum stearate and aluminum hydroxide, which created a paint that was unnaturally short and would not level, unlike more simple oil paints that lacked such fillers/stabilizers. Hand ground paints were less likely to contain these fillers, and therefore, did not exhibit that defect. This dichotomy contributed to the deification of cold pressed oil well beyond the virtues of the material…or at least this is my take

    We have a few paint makers on our moderating board and industry cotacts and I look forward to their responses to this thread.

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    ​Thanks George.

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    There should be no problem in terms of paint adhesion/etc for you to paint directly on the shellac sized panel. The only issue would be the color of the panel. Depending on how dark the wood is, this would be visually similar to painting on a mid-toned or even dark colored ground. We know from examining old oil paintings that oil paint can becomes more transparent overtime. This is mostly, but not completely, the result of a chemical change in lead white and even zinc white paints. Thinly painted lighter or even mid-valued paints can become darker because of this increased transparency. This sometimes resulted in an exaggerated contrast effect where the darks became slightly darker, the midtones disappeared, and the thickly applied highlights remained light. Othertimes, it caused an overall lowing of the value and intensity of the painting.

    We are not sure if paintings made with titanium white will exhibit this increased transparency of time but it is unlikely to do so to the same degree. We now know that oil painters should avoid the use of zinc white for a number of reason. I am also definitely not suggesting that oil painters should avoid lead white. It is really the best oil paint that we have in terms of preservation. Additionally, there are plenty of paintings from the 17th-21th C. where that artist left portions of their wooden panel exposed for a specific effect. We just do not know the degree to which these have shifted overtime. What I am suggesting is that a painting executed on a darker color (like could be the case with shellac sized wood) should not be painted too thin if the artist wants to avoid possible changes overtime.

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    Calcium carbonate derived from different mineral sources behave differently in paint. The material can be ground from limestone, a sedimentary rock formed in sea beads or alluvial deposits; or marble, which is limestone that has undergone heat and pressure below the earth's crust; or chalk, a light, low structure material normally associated with the sedimentary deposition of the shells of such minute marine organisms as foraminifera, coccoliths and rhabdoliths. The particle structure and chemical behavior of these variations of calcite all differ slightly.

    The particle size and shape of calcite in regards to the behavior and performance of paint are important for several reasons. One is the viscosity of the paint, which is related to the volume occupied by the dispersed solids within the paint vehicle.

    Another consideration of the influence of particle size and shape on the behavior of paint is the surface area of the particle. The amount of paint binder required by a pigment to form a paste paint is called its oil absorption (OA) number. The greater the surface area of the particle, the more binder it demands to make into a paste or flowing paint. Synthetic (precipitated) calcium carbonate that consists of 0.05 micron needle-shaped particles has more surface area than the particles of ground limestone of the same size, which have simple structures resembling rhomboidal crystals. Because of the complex surface of the precipitated calcium carbonate, it will tend to scatter more light and consequently appear more opaque than the ground limestone particles. However, it is likely that this precipitated calcium carbonate will consume considerably more binder than the ground limestone.

    Selecting the right type of calcite, taking into consideration particle size and shape, brightness, chemical constituents, and surface treatment are important factors when it comes to making paint or oil painting mediums.

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    If you are diametrically opposed to the use of alkyd mediums despite their good track record, there are a couple of options. Choose only paints composed of fast drying pigments (lead white, umbers etc) or the judicious addition of driers.  I am adapting one of my responses to another thread as it is applicable here.

    I generally do not recommend that artists add driers to their paints and mediums because it is way too easy to add more than necessary and risk compromising your paint film over time. If you performed systematic tests and only added just the amount necessary to make a paint that dries in a reasonable amount of time (a couple of days) this should be safe. If it were me, I would make up a batch (eg 8 oz) of your chosen solvent (eg odorless mineral spirits) and add a few drops of drier. Then add this to a blob of paint diluted in the manner that is typical for you. Test how many days this takes to dry. If it is still too long, add another couple of drops and try again until you figure out the proportions necessary to create a drying rate that meets your requirements. Do not add more than necessary.

    Others may have additional thoughts.

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    First, shellac would not be my first choice for a size for wooden panels but it should be perfectly serviceable. It does benefit from being delivered in a non-aqueous solvent. This means that the wood will not have its grain raised or issues of warping caused by the application of a shellac size. A size should never be applied so thickly as to create a discrete layer and certainly not a glossy surface. Any size applied too thickly will cause problems with adhesion (actually this is less of an issue when painting acrylic dispersion colors on acrylic dispersion grounds since the acrylic dispersion binder is such a good adhesive as compared to oil paint) . See our section on sizes in our “Resources” section for general issues about sizing.

    If the shellac is applied in a dilute enough state that is cuts and evens out the absorbency of the panel but does not create a discrete layer which would eliminate mechanical adhesion of the ground and paint layers, this should be a trustworthy panel. Whether these specific panels are “acceptable and durable” would relate to the above as well as what type of panels they are sealing with shellac. No size is likely to make a junk panel acceptable.

    There is actually a long history of the use of shellac as a preliminary application before oil paint in the house painting trade. I seem to remember reading a house painting manual from the early 20th century where it said to, “give the wall a good drink of shellac before painting in oil paint,” or something to that effect. I just checked and R. Mayer also mentions this reference.

    Now, the above is specifically about the use of such a size under an oil ground and oil paint. I can see no reason to use a shellac-sized wooden panel for subsequent acrylic dispersion grounds and paint. In that case, it would make more sense to size the panel with acrylic dispersion medium or perhaps PVA size. Animal glue, if one choses to use it despite its reactivity to the environment, should only be used under oil and alkyd layers.

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    For problems with ripples and loss of tension while sizing, I recommend looking at the stretching technique first. If the fabric is losing as much tension as the images in your linked blog post, in my opinion, the canvas may not have been stretched properly.

    Pulling directly across the stretcher frame (the method most artists are taught) can result in uneven tension from spot to spot. It can be challenging to pull with the same amount of force at the corners as in the middle of the bars, even with canvas pliers. An alternate method- stretching diagonally on the bias- evenly distributes tension by displacing the entire network of warp and weft, avoiding tight spots along the span of each stretcher. Also, tacking on the sides of the stretcher rather than the back yields better results.

    I would abandon any further attempt to size canvas off the stretchers, as loose fabric. There's no way to maintain a flat plane or consistent weave pattern this way.

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    The intention is to mix the chalk with oils, correct? Mixing calcium carbonate (or any absorbent filler) with acrylics can significantly affect film strength.

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    Hi Hector

    First, if you are wishing to make a more transparent, yet properly bound paint by adding some form of calcium carbonate, you should really mull the calcium carbonate up into your chosen drying oil to a loose consistency and add this to your paint. Simply adding calcium carbonate to your paint will only make it leaner but would also make it slightly more opaque. Adding too much calcium carbonate in dry form to your paint would result in a film that is underbound, and may be prone to powdering, sensitivity to solvents, and even delamination.

    As to the type of calcium carbonate, while they would all be chemically identical, and would in theory be capable of making a well bound paint that was more transparent, it is really the particle size and shape that contributes interesting handling properties. Only you can decide which are of interest to you. I know that ground calcite is popular but I am not sure about the particular grind commonly used and how that will influence paint handling. I have not personally performed a ton of experimentation using different CaC03 powders to influence handling but I know others have and hopefully they will chime in with suggestions.

    A related question was rather fully discussed here on MITRA and that thread may be of interest to you.

    https://www.artcons.udel.edu/mitra/forums/question?QID=111

    The following thread is only peripherally on topic, but you may find the later portions of interest.

    https://www.artcons.udel.edu/mitra/forums/question?QID=174

    All the best

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    Thanks George. Very cool/ surprising info and results.. Thanks for the follow up and response.

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    ​Based on Ben's comments, we created a test panel on copper substrate with the following grounds:

    1. Rublev Colours Lead Oil Ground

    2. Rublev Colours Lead Oil Paste Ground

    3. Rublev Colours Lead Alkyd Ground

    We also made two samples of lead white dispersed in linseed oil containing paint with free fatty acid (FFA) value of 12 (Sample 1), and another with FFA of 4 (Sample 2).

    In addition half of the panel was rubbed with a fresh garlic clove and allowed to dry before applying the grounds and sample paints.

    As the grounds dried, ground 1 exhibited a green tint on the area not coated with garlic juice, whereas on the area coated with garlic there was no change in color. Grounds 2 and 3 dried without any change in color on either the uncoated or garlic coated areas.

    Paint sample 1 had a slight green tint, but not nearly as strong as the tint of ground 1 on the bare copper surface. Sample 2 exhibited less tinting than sample 1.

    Interestingly, we measured the rate of drying of the paint films on the bare copper and the side coated with garlic, and noted that paint on the garlic dried at a much slower rate.

    Grounds 2 and 3 have FFA values less than 1, whereas ground 1 has an FFA value greater than 4.

    The simple test demonstrates that free fatty acids in linseed oil react with copper to produce a green tint. However, it does not explain the degree tinting in ground 1, since the FFA value of ground 1 is less than sample 1.

    We are investigating this issue further to determine the differences, but in the meanwhile, we are recommending the use of ground 2 or 3 as a ground for copper.

    As an side, we formulated Rublev Colours Lead Oil Ground for porous substrates, such as wood and canvas, but not for non-ferrous metal substrates such as copper or aluminum.

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    Stand oil is not the best choice if you are trying to avoid leveling. Its inherent quality is to level. Linseed or Walnut oil sun thickened mediums, or to a lesser extent, artificially oxidized oil mediums, will be better for this as they tend to set or hold their shape, and set before leveling. Probably the best that I have found for this effect for a black or dark paint is thinning it with a dilute true copal-oil varnish (or possibly a true amber-oil varnish) as they both set quickly and resist the action of restoration solvents in the long run. I mention dark oil paint because both of these will darken substantially and dark pigments will be less effected by this change. I will probably get some push back on this as these materials are controversial in the conservation world for many reasons including brittleness, and yellowing. Used in this way and in fine isolated strokes as described there should be no preservation problems. The problem here is that true Congo, Zanzibar, and other hard copals (and true amber varnish) mediums are either unavailable or very expensive. Really, there is little benefit of these mediums over a high quality fluid alkyd medium for this purpose. I personally find the gelled alkyds less useful for this purpose.

    To the 2nd question, 1:1 mixed with what? 1:1 oil (or even resinous media) to oil paint is way too fat for anything other than special effects, and probably too much regardless, unless you are willing to deal with the eventual strong yellowing  that will inevitably occur. 1:1 oil paint to 1:5 oil solvent may be perfect. It may also be too thin for certain FINAL effects. We need to maintain a bit of rationality in this and you should be able to come up with a sensible ratio.

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    ​Your question is a good one as it is easy to be confused with the term "pine resin" when sifting through the technical literature regarding the analysis of Old Master paintings. The reason why it is hard to get a sense of just what is meant by this term is that it is INTENDED to be a general descriptor; often conservation scientists will use this term when they only have a general idea as to what is detected during analysis. First a bit of background on "pine resin"….I will limit my response here to focus on paintings that are well over 100 years old as this is what you appear to be most interested. Each member of the Pinaceae family (pine, larch, and others) possess chemical markers that can in theory be distinguished using methods like gas-chromatography/mass spectrometry. However, the principal markers (the diterpenoid abietic acids) will all eventually undergo oxidation and ultimately this makes it difficult to identify their origin. So time is really against us here if we are ever to find out for sure the original source of these markers….in general all you can really say is that "pine resin" (likely rosin or colophony) was detected but in theory these markers could derive from other Pinaceae sources as well. Secondly and perhaps more importantly is that there is really no way of knowing at which point these pine resin markers became an integral part of the painting's history. These pine resin markers could indicate that the artist originally added some rosin, colophony, and/or related material to their paints and/or varnish coatings. BUT it is equally possible (and likely) that these markers derive from unoriginal restorations or treatment campaigns. Realize that these materials were traditionally used in varnish coatings, wax-resin lining recipes, and even cleaning formulations in the past. So it is not surprising that we often detect their presence in rather old paintings, particularly ones that have been treated numerous times. So in summary I would say this: our instruments are not quite there in terms of being able to paint a definitive picture regarding what Old Master painters used in their binding media. We can really only say what our instruments detect…the fact that the majority of these paintings have been restored time and time again really complicates our interpretation of the analytical results. We had far more faith in our ability to analyze pictures in this manner some 20-30 years ago but now we know better. That being said we cannot really say that van Eyck and others did NOT use resinous additives. They very well may have….sometimes small additions of resinous components are below the detection limits of our instruments so it is possible that we cannot even identify minute additions. But when we do find these markers it is really impossible to know where they originate from. I do encourage you to continue working and experimenting with these types of resins if you enjoy using them and find that you can accomplish certain effects that are to your liking. I would only ask that you read over our "Mediums and Additives" document in the resources section so that you can take the necessary steps to ensure that your paintings are properly cared for in the future. I hope that somewhat answered your question. Finally, there is a brief outline that describes the origin of various resins and varnishes that can be found on the Kress Technical Art History Website here for addition information.

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    You are very welcome. "Cured" in quotes - just as you did -  is definitely accurate as technically curing refers to chemical changes usually triggered by a substance or energy source. Thus you can have moisture, heat, and UV cured coatings, as well as two-part systems where one part acts as the catalyst. In water-based acrylics, however, the polymer chains are already fully formed and suspended in a dispersion and a more accurate description is that once the water evaporates and the polymers are pushed together, they begin a process called coalescing where the polymers entangle and fuse together into a continuous film. It is that process that continues for quite some time - certainly out to a month or more - but the question becomes at what point can it safely be painted over, and at least for us at Golden, 2 weeks is a good practical timeframe to aim for, with a month being more of an ideal.

    Sarah Sands, Senior Technical Specialist, Golden Artist Colors

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    Just as waiting 6-12 months for an oil ground to cure is better than a week or two, waiting longer after applying acrylic gesso can only help that film fully dry and acquire more of its final, long-term traits. That said, the vast majority of the moisture that will come out of an acrylic gesso film - especially on canvas - will do so in the first 72 hours, which is what we give as a minimum timeframe, while two-weeks is our usual recommendation - but we would not quarrel that, if you can wait, a month is even better. The fact is, there will always be moisture in the gesso - just as there will always be moisture in the canvas and wood we use, as materials reach an equilibrium with their environment. For an acrylic film, in typical ambient conditions, that is in the 11-16% range, which is about the same level of moisture in wood, which of course can be primed with oil-based paints. You can read some of our research in this area in the following issue of Just Paint:

    http://www.justpaint.org/wp-content/uploads/2015/11/jp27.pdf

    As you look at the graphs there keep in mind the “thinnest” film shown is quite substantial - 1/16” - and a brushed on film of gesso, especially on canvas, will reach those equilibrium levels much much faster. And keep in mind, that on canvas evaporation will continue to happen in the rear of the canvas, so even after one paints further consolidation is taking place.

    Hope that helps. On a final note, in my experience, if you prime several canvases and decide to paint on one of then after 3 days or a week, the others will almost invariably sit around and continue drying and by the time they get used a month or more would have passed.


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    Hi

    I know from a forwarded correspondence that your primary issue is the slow drying rate of your oil glazes. I applaud you for refraining from adding large amounts of soft resins to your mixture to speed up the setting of the glazes. This is a common, but lamentable, practice (see our "Resources" section for more info on this subject). I do wonder how much medium you are adding to your paint to create glazes. It is good painting practice to only add enough medium to make a paint that can by physically manipulated to a thin glaze and not to dilute the paint with so much medium that you create a “watercolor-like” wash. I will assume that you are adding a reasonable amount of your stand oil-turpentine mixture.

    My first response to a query like this would be to suggest an alkyd medium. You have made clear that you are not interested in that. I also know from your previous email that you do not trust this medium. I am not going to try to persuade you here but feel the need to comment on this for the benefit of others that will read this thread. Oil modified alkyd resins have been in use since the 1920s and have stood the test of time. They remain more flexible over time than oil paints and paints that incorporate them are less soluble to the action of organic solvents than a paint that contains only a drying oil in the same proportions. This is a separate issue than if one does not like the feel or rheology of paints containing alkyd medium. Honestly, I never liked the feel of oil paint with an added gelled medium. I have less of a tactile objection to fluid alkyd mediums.  

    Anyway, alkyds are out for you. I wonder if you could substitute a faster drying bodied oil (homemade sun thickened oil comes to mind) for the very slow drying stand oil.

    If you really do like the stand oil/turp mixture and only object to the dry time, I wonder if it would not be a good idea to just add to your medium a few drops of cobalt drier, or even better a system drier (a mixture of metal salts known to accelerate the oxidation of oil films).

     I generally do not recommend that artists add driers to their paints and mediums because it is way too easy to add more than necessary and risk compromising your paint film over time. If you performed systematic tests and only added just the amount necessary to make a glaze layer that dried in a reasonable amount of time (a couple of days) this should be safe. If it were me, I would make up a batch (eg 8 oz) of your dilute stand oil medium and add a few drops of drier. Then add this to a blob of paint and create a typical glaze. Test how many days this takes to dry. If it is still too long, add another couple of drops and try again until you figure out the proportions necessary to create a glaze that meets your requirements. Do not add more than necessary.

    I hope that this was of some help. Feel free to post a response if I somehow missed the point of your question. Additionally, others may have suggestions that I did not think of.

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    ​To the original poster: It seems that the jury is still out regarding your specific question. What I would state is that cotton fibers in general are much shorter than flax (linen)...this can certainly contribute to potential deformation later on down the road. Speaking from personal experience I tend to see more planar deformations occur in cotton duct canvases than in linen but more research needs to be done in order confirm my observations. All in all such deformations can be readily dealt with by conservators....I would just ask that you consider using a stretcher with expandable corners or even stretching your large format canvas over a rigid support (backing boards are also good). Hope that is of some use.

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    ​We recently heard back from one of our scientists (Dr. Chris Petersen, a retired organic chemist who formerly worked at Dupont). Here is his comment:
    "There would be minimal penetration of the vapor if the paint is simply exposed overnight; clove oil is a phenolic type antioxidant with a boiling point >250 deg. Surface penetration is actually what you want if you are tyring to prevent the drying effect that is propogated by oxygen promoted free radicals. The stuff does have a strong odor so even a small amount in the air is overwhelming. As an interesting aside, phenolic antioxidants are used to stabilize acrylic monomers like methyl methacrylate so they can be shipped and stored in bottles. When you add an initiator to make a polymer, the inhibitor is consumed and the free radical reaction occurs."

    So in summary there would in fact be some penetration, albeit minimal. Dr. Petersen therefore also believes that this would not drastically impact the "health" of the paints in the immediate future. 


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    ​Also I am posting this on behalf of conservator Laura Fuster: 

    I thought the artist might find of interest the proceedings of the symposium ‘Copper painting and other metal plates: production, degradation and conservation issus’ held last January at the Polytechnical University of Valencia are available at : http://www.lalibreria.upv.es/portalEd/UpvGEStore/products/p_2102-3-1 ‘Copper painting and other metal plates: production, degradation and conservation issues’ ‘La pintura sobre cobre y otras planchas metálicas: producción, degradación y conservación’Edited by L. Fuster, I. Chulià, MF, Sarrió, ML. Vázquez, L. Carlyle, J. Wadum226 pagesFull color, 22 chapeters (18 in English, 3 in Spanish)ISBN: 978-84-1684-696-2

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    ​We have representatives from Amperstand on our industry contacts so I will send them this question to answer.

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    ​Hi -

    Using GAC 200 in this way is fine, just keep in a few things in mind:- it is only water resistant and not waterproof, and certaainly a polyurethane would produce a harder and tighter film. 

    - when using GAC 200 alone and creating a continuous film, we recommend having it dry at a min of 70F. Otherwise there is a chance of  microscopic microfissures forming that are not really visible to the naked eye. We noticed this when testing GAC 200 as a size for blocking oil. When dried at 70F or above the films were succefful at blocking oil, while below it grew increasingly able to allow small amounts of oil to penetrate through.

    - if the above is concerning, you can add some GAC 500 to give some additional flexibility and a lower film forming temperature. A 3:1 GAC 200:GAC 500 ratio would be good. You should still have a nice low tack film.

    -  if you are finding hardboard to be prone to damage have you considered using something more substantial such as MDO (Medium Density Overload)? Because it comes with a resin impregnated paper facing on face and back, there would be no need to seal the back per se.

    - finally, if wanting to really isolate the panel from moisture, take a look at this article we published on our Just Paint site on priming panels for outdoors:

    https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjHuuaG98HXAhUDQCYKHeeiA54QFggoMAA&url=http%3A%2F%2Fwww.justpaint.org%2Fpreparing-panels-for-a-life-outdoors%2F&usg=AOvVaw3utTSHP8is6Uv73hiqjrpV

    The alkyd primers used there should give a harder surface and be more moisture resistant.

    Anyway, those are at least some thoughts. And if you like what you are getting, then there is no reason to change.

    Hope that helps.



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    ​I was uneasy about the statement that most commercial artists' canvases were composed of blended fibers but refrained from commenting until I heard from someone in the industry. I received this comment today and am posting it for them. Their response is in black.

    The majority of commercially available artist canvas is not PolyCotton.   

    https://www.artcons.udel.edu/mitra/forums/question?QID=341

    Artist Canvas is available in three distinct categories:

    1) Linen - this is fabric that comes from the fibers of the Flax plant. It is very sturdy and durable. (warning - much of the canvas from Asia that is referred to as linen is a 100% cotton fabric that has been dyed to look like linen)

    2) Polyester and/or PolyCotton blends - synthetic fabrics or synthetic blends. This is especially prevalent in student grade canvas panels and works great for smaller stretched canvas.

    3) 100% Cotton - The majority of Artist Grade Canvas is 100% cotton. A great example of 100% Cotton Artist Canvas is the Fredrix Pro Dixie or the Fredrix Red Label Cotton Canvas.

    We’d be happy to send samples to your industry expert if you’d like.

    Best wishes,

    Paul Straquadine

    VP Sales Tara Materials/Fredrix Artist Canvas

    322  Industrial Park Dr

    Lawrenceville, GA 30046

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    There are a couple of comments here.

    As to the sandpaper, yes, it is important to abrade the surface to provide tooth and the solvent is used to degrease the panel.

    Ben, most copper corrosion products are in the green to bluish green color spectrum. These products range drastically in terms of reactivity, stability, and effect on the copper object. Copper chloride also known as bronze disease is at the bottom. This means that the form of corrosion that occurs between the copper and any oil ground or paint will have an effect on the stablity

    Ben, your friend’s supposition about the sulphur promoting a specific chemical reaction which may be more stable, that was precisely what I was alluding to in my initial response. My first draft mentioned sulphur containing thiol groups and the preferential creation of more stable sulphur containing copper compounds but edited that out. Perhaps this limits the degree of the greenish corrosion but on the other hand, sulphur is one of the things known to promote darkening of lead white oil paint so…there are still questions here. Again, I do not believe that garlic juice is a necessary step but its use is interesting.

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    ​Hi

    I cannot specifically state what the Old Masters for this purpose, as there is little archival documentation and organic analysis is far more complicated than was once believed. I would suggest that any additions to the paint were rather simple and not likely to contain high proportions of soft resins like mastic or the resin in larch turpentine. The reason that I say this is that fine thin lines applied over dry underlayers are the most susceptible to abrasion and yield under the actions of strong solvents and extreme pH. These were precisely the materials used by restorers in the early days. If it was common practice to add large amount of soft resin to the paint, there would be few examples of these fine lines on Old Master paintings for us to see today. The danger of this practice is obvious when examining 19th century maritime paintings where the rigging is often completely abraded away when the artist used a lot of resin to accomplish these fine lines and/or when a poor restorer cleaned the work without the knowledge and sensitivity needed to clean such works.

    I would separate the methods of the Renaissance and Baroque from those of the 18th and 19th centuries when it was almost universally accepted practice to use mediums with very large amounts of soft resins. This is an instance where mediums containing hard resins and oils yielded more stable results than did the mediums containing softer resins (BTW I not stating that resins are necessary). The less soluble hard copal and amber mediums (if amber was ever a common paint additive is a completely different debate) create a paint film that is more resilient to the actions of cleaning. The oil-fused hard resin mediums did tend to yellow strongly and become brittle if used indiscriminately. Today we do have alkyd mediums, which fulfil the same role but are less yellowing and more flexible. Whether you like the way that they feel and move is another issue. I have generally preferred the fluid alkyd mediums to those that have a gel-like consistency or an intentional thixotropic quality in emulation of megilp.  

    So as to practical application tips, I do think that some addition of a long oil like stand or sun thickened oil in a suitable amount of solvent added to the paint will help. The couch of oil will make this easier but the practice is problematic. This is the same issue as that of oiling out. Any oil film that is not covered by a layer of paint will eventually darken and become obvious. This may be minimal if the application is extremely thin, but even then it will probably become visible in the long run. You may be interested in browsing through the section on oiling out in “Resources Section” to read a bit more about this issue.

    It seems to me that after the skill of the artist, the most important factor is the choice of brush. In my experience, the best are high quality kolinsky rounds with longer brush hairs. There is a reason that there is a brush made specifically for painting the super fine lines used to depict the rigging on ships. These very long rounds are even called riggers. Now these may be too long for your needs but you get the general idea.

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    ​Thanks Brian. As for your aside - you clearly are one of those painters ready to pounce!

    Ugh - I know.   :)

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    Sarah

    Good info and call on the Incralac. That slipped my mind but makes sense in this context. You are completely right about the probable superiority of other substrates. It is true about the allure of the visible copper surface but it is also true that a very high proportion of historical oil-on- copper panels had some sort of ground. This does bring us to one of the fallacies mentioned in the "Resources Section" just because some noted master of old used a material does not ALYWAYS mean that it is still the best tool for the job. As an aside, I always pounced my lead white ground with the palm of my hand (protected by wearing a nitrile glove) very thin so that the sheen of the panel could still be discerned through the thin ground layer.

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    ​Hi -

    I only have a few things to add to Brian's comments.

    But first I would want to ask why you are choosing copper in the first place, especially if willing to prime it - thus losing any of the metallic, reflective sheen that painters like Claude Lorrain were attracted to. And beyond that is the simple fact that copper remains a reactive metal and there are definite mechanism of degradation of oil on copper that are a real concern. See The degradation of oil painted copper surfaces by Lydia-Chara Pavlopoulou and David Watkinson for a good and current summary:

    https://www.academia.edu/1031822/The_degradation_of_oil_painted_copper_surfaces

    Certainly the analysis doesn't mean that all paintings will fail - only that they are vulnerable given the potentially reactive nature of the oil/copper interface. It would see to me that if wanting something that is more stable and equally rigid and lightweight, that aluminum-composite panels - such as Dibond - might be a better option.

    That said, I have certainly done my own share of oil painting on copper - although nearly always painting directly onto the copper - so know the allure. It was also a useful way for me to 'recycle' copper etching plates that students in printmaking departments would abandon at the end of the semester. 

    As for the other points, I can share a quirky test we have done of soaking bits of copper into various oils (both linseed and safflower) to look at the ability of the oils to become infused with copper ions. Its mentioned in literature as one way to make a fast drying albeit 'green' oil. Curiously, only one of the oils turned green - and from what I recall it was the one with a higher acid value. But not sure. So it might be the same with the grounds you are using - one or more of them might have an oil more prone to react with the copper.

    And one last thought - in terms of sealing the back - you might take a look at a product called Incralac, which you can find at conservation supply houses like Talas:

    http://www.talasonline.com/search?keywords=incralac

    It was formulated to protect copper and copper-alloys from corrosion, and while used principally on sculpture and objects, we have used it successfully as a form of clear primer on copper when priming with acrylics. A bit of an off-label use but we feel fairly safe. It might be a useful product to protect the backs of your plates and perhaps even as an isolating coat between the copper and the primers you are using? That latter I don't know and you would need to test adhesion and make your own assessment.

    Hope that helps.


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    Hi. Thanks for the kind words. I will respond within the text and in red

    I've searched here on the topic, and also read the "rigid supports" document in Resources (which is a wonderful reference), but I have a few additional questions about working on copper. 

    1. I'm using relatively thick copper (14-gauge etching plates) and working fairly small (maybe 11x14" or so, down to 5x7"). Is it necessary to brace supports of this size, or would it be sufficient to put a lightweight (floating) backing board behind the plate in the frame--perhaps Gatorfoam, or a layer or two of museum board? 

    I do not think that bracing would be important or even a good idea in that case. What you propose sounds fine and is exactly what I have done in the past. It may be a good idea to put an acid free interleaf between and board that may be acidic or become acidic to prevent corrosion of the reverse of the copper panel.

    2. My process to prepare the surface of the plate: degrease with denatured alcohol, thoroughly abrade the surface with sandpaper or steel wool (with the aim of completely stripping the surface to expose fresh metal), vacuum off any copper dust, then degrease again, making sure that all dust and residue gets removed. Then allow to dry, and prime. Does that sound about right?

    That sounds good.

    3. How about where the copper is not covered by primer/paint? Like the back and sides? Can I just let that oxidize, or should I seal it with something? Renaissance Wax, maybe? 

    I believe that most 17th century oil on copper panels were not coated on the back. There are even a few instances where the work was done on the reverse of an etched intaglio plate. However, if you wanted to avoid corrosion on the back you could spray it with an epoxy coating after degreasing the reverse. Do this before treating the front so that your degreasing and abrasion of the front would remove any accidental overspray that may have gotten onto the face of the panel.

    4. I assume any oil-based primer will work? How about an alkyd primer, like Winsor & Newton's Oil Primer? I have a few small test sheets on which I tested some straight lead carbonate in linseed oil (RGH), a lead painting primer that contains some titanium white and driers (Rublev), and the Winsor & Newton primer. All three dried very quickly (the W&N primer was touch dry in a matter of hours). I'm guessing that the copper is a drying catalyst? The Rublev primer turned very green upon drying; I don't think that it was a matter of surface prep, because the RGH lead primer is right next to it on the same sheet of copper, and it didn't change color at all. The Winsor & Newton primer took on a slight green tint, but it's barely noticeable. Is this sort of thing common? Something to worry about? I don't think I'd use the Rublev primer, since the color change in that case was considerable. 

    For me, priming copper panels has had a bit of voodoo to it. I have primed a group of them at the same time and using the same prep and materials and had one of the bunch turn green as well. These should be cleaned of their ground and the process repeated as such immediate corrosion is a sign of trouble, which would likely only continue if left in place. Copper can catalyze drying oils but I am also guessing that the primers contain enough driers to create a rapidly setting ground. I am unsure why the primers all preformed so differently. Perhaps they employed oils of very different acid numbers. It makes sense that an oil ground would be formulated with an oil of a higher acid number as this tends to make a paint that contains a greater percentage of pigment but one that yellows a bit more strongly. The leaness would be useful in a ground and the yellowing would be far less of an issue than in a paint used for surface effect. Again, all of this is conjecture.

    If you have the time, it would be useful to make a test of the available grounds and let them really oxidize for a while and then test for scratching before deciding on your preferred ground. I have always used lead white in linseed oil without a drier. There may be better modern materials for this but I have not personally tested them. I know that there has been a good bit of experimentation with various coatings on aluminum panels. I will send this along to a couple of our other moderators to see if they have anything to add.

    5. I skipped the oft-recommended garlic step, just on the basis that I have been able to find a consistent or empirically supported reason for its use. Some sources say that it helps to "etch" the metal (though it is unclear how, since garlic is not acidic). Some sources say that it might serve as a wetting agent (which makes more sense, except for the fact that copper doesn't seem to need a wetting agent--it takes oil paint really well, with no beading). Some sources say that it helps the paint bind to the surface chemically, rather than just mechanically, but I don't think that's correct. Don't oil films exchange ions with copper? In any event, the idea of putting an aqueous paste between the metal and primer seems like a bad one to me, but perhaps there is a purpose for this step that I haven't considered?

    I do not think that garlic is necessary for a stable panel. Garlic is not very acidic but a cursory internet search shows that it has a pH of around 5.8, which is well below neutral (7). However, I do not believe that etching plays a major role here no matter what. The dried garlic juice does create a slightly pebbled or textured surface that may promote adhesion.

     As to whetting, I have personally seen thinned lead white ground bead on a copper panel that did not have such a layer. This may have just been an isolated occurrence or perhaps that panel was not sufficiently abraded.

    I have discussed this idea with a fellow conservator who is more science savvy and they suggested that the garlic may also perform an additional effect; promoting a more stable form of corrosion. The copper is going to corrode to some degree at the interface between the panel and the oil primer (perhaps there are modern materials that would not do this) All cross-sections of paint taken from oil on copper paintings that I have seen exhibit a green layer at the bottom of the oil priming. The sulfur in the thiol groups contained in garlic may promote the creation of more stable corrosion products.

    In closing, though, I do not believe that the garlic application is necessary nor does it absolutely make a more stable panel, I do believe that people did believe that it did, and that this was because of some of the aforementioned reasons.

    Thanks!

     

    -Ben

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    I will assume that you are talking about the use of isolation varnishes between layers of oil paint. Isolation varnishes between disparate paint systems are a different idea and may or may not be advisable (eg applying a coating over a very absorbent aqueous paint system to cut the absorbency before applying oil glazes) Also, the concept is different with some other mediums. I can see no really issue with using clear interlayers of acrylic dispersion mediums between layers of acrylic paint. Acrylic dispersion are an excellent adhesive, where drying oils really are not.

    This use of isolation varnishes in oil painting should be discouraged for a number of reasons. First, it is generally a bad idea to reduce the mechanical tooth of a paint layer, which could promote delamination or flaking of the superimposed layer.

    Second, adding the varnish layer between paint layers will introduce an unnecessary solubility issue. Even if it is covered by additional oil layers, the varnish could be attacked and undercut during a restoration campaign resulting in the loss of all subsequent layers. For instance, a layer of natural resin between paint layers will create a paint stratigraphy that is sensitive to hydrocarbon solvents, even those containing a low proportion of aromatics. A layer of shellac between oil paint layers introduces a sensitivity to alcohols, etc.

    Additionally, the use of varnish interlayers creates a more complicated paint stratigraphy. We know from examination of historical paintings that the more complicated the stratigraphy, the more likely there will be some failure in the future. This does not mean that one has to create paintings in only a few layers, but you should aim to use as few layers as is necessary to create the desired effect.

    The varnish interlayer will also respond in a different manner to movement of the substrate than will the paint layers below and above it. It will also age differently. The flexibility of the varnish may change drastically over time making it less flexible than the layers that it is covering. Etc, etc. So, for the above reasons, and likely many that I am not thinking of at the moment, it is really best to avoid the use of isolating varnishes in oil painting.  

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    Most commercial cotton canvas offered today are actually blends of cotton and polyester fibers. Some cotton canvas we have studied consisted of as much as 65% polyester in both the warp and fill weaves.

    It i