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  • Question asked 2019-03-24 17:21:16 ... Most recent comment 2019-03-24 22:43:17
    Flexible Supports

    ​Are either considered to be more ideal in stretching canvas?

    I've used both and find the tacks to be a little more adjustable.  That is to say I can more easily remove and reposition them.  Though one wonders about the impact shock from hitting them in.  On the other hand the staples also seem to go in with quite a "bang".   Not much of a concern with a yet to be primed surface, but what about restretching old paintings?  Could old paint be loosened from the canvas?

  • Question asked 2019-03-24 17:53:34 ... Most recent comment 2019-03-24 22:30:35
    Flexible Supports Oil Paint Art Conservation Topics

    ​Apart from possible aesthetic considerations, a polyester canvas would seem a more ideal flexible support than linen or cotton, at least in longevity.  Less reactive to humidity, embrittlement and bacterial attack, it would appear almost perfect.  

    Except, what about heat?  What damage would occur should some future person try to iron it down to another support?   Would the polyester reach a temperature likely to cause damage in a way that say, linen wouldn't be in a similar procedure?  When using a polyester canvas should we make sure that we find some form of pre heat shrunk material?  Is this even available, or is it something already standard in polyester artist canvases?

  • Question asked 2019-03-24 14:35:27 ... Most recent comment 2019-03-24 19:07:43
    Oil Paint Paint Making Mural Painting

    ​Hello Mitra,

    I am going to make some large format paintings for certain commissions.  Since the paintings are extremely large i find tube paints inadequate because they are too "short".  Although i know tube paints are grounded to perfection they dont leave "long " and flowing brushstrokes that will allow me to work faster and in the style i want.  

    Since these paintings are going to be alla prima, I want a fast flowing paint that its vehicle is adequate for what i want and also not going to self destruct because of poor formula for the vehicle.  

    Is there a wax and linseed oil formula that can be recommeded?  I say wax because i heard that  wax would give me a "long" paint.  

    If wax isnt adequated what does Mitra recommend? 

    Thank you,


  • Question asked 2019-03-21 13:40:15 ... Most recent comment 2019-03-21 18:35:14

    I am working on some definitions; the definiton I am working on right now is glair.

    My first step is reference books and then I go to primary sources whenever possible. My resources, older reference books, state that glair is used for bookbinding, gilding, and painting watercolors on parchment. I talked with one bookbinder and he gave me his recipe for preparing glair and said it was used most for tooling and gilding simultaneously. He said that he used a “bone folder” (non-metal) for folding vinegar and skim milk into frothy egg whites that had set. However when I tried to verify with other book binders no one had heard of it. Is my first source reliable? Is the term bone folder in common use?

    I also contacted artists working on parchment. Only one had heard of glair and she didn’t know if it was still in use. She later said that one of her colleagues uses glair with dry pigments when painting and gilding on parchment but she didn’t know if he made his own glair or bought the commercial variety. Does anyone know the pros and cons of handmade glair vs. commercial glair?

    Thank you in advance for your help.


  • Question asked 2019-03-20 15:19:08 ... Most recent comment 2019-03-20 17:25:32
    Art Conservation Topics

    ​I have a painting when my apartment whas broken into they spray painted a Texas longhorn emblem on it, I believe the painting is acrylic can the spray paint be removed and not destory the painting?

  • Question asked 2019-03-19 15:28:02 ... Most recent comment 2019-03-20 12:09:16
    Chalk Egg Tempera Grounds / Priming

    Over the years ​I've tried various chalks (calcium carbonate) and gypsum (calcium sulphate) to make gesso. I've come to prefer a fine marble dust, for hard to define reasons: it's a bright white, has the right "feel" of hardness to me, and admittedly I probably like the idea of working with ground marble.

    Within the two general categories of chalk and gypsum there are many different products available, differentiated by source, type of grinding, processing, natural coloration, etc.  Is it correct to say that these properties don't affect the quality of the gesso, rather they merely reflect individual artist preference (such as my own mentioned above)? Are these differences actually perceptible (aside from the obvious visual one of coloration)?  

    Finally, is there any reason to make a egg tempera ground (final layer, not initial) using a medium or coarse grind chalk or gypsum, or would that increase porosity/absorbency too much?


    Koo Schadler

  • Question asked 2019-03-18 10:00:33 ... Most recent comment 2019-03-19 09:21:21
    Varnishes Studio Tools and Tips Health and Safety

    ​Hello MITRA,

    How long it takes for turpentine to evaporate from a freshly applied layer of dammar varnish over an oil painting with dimensions 80X60 cm?

    I plan to invest in local exhaust ventilation (LEV), so it would filtrate varnish vapor. In this process I would varnish painting inside a LEV hood. I don't konw how long to keep it inside.

    Kind regards,

    Damir P.

  • Question asked 2019-03-15 13:06:25 ... Most recent comment 2019-03-15 17:44:33
    Egg Tempera Rigid Supports Grounds / Priming

    I have two questions regarding my particular case of preparing cradled plywood panels for egg tempera painting

    1. Will traditional RSG and/or RSG gesso adhere to a panel that has been sprayed or brushed with Shellac?

    2. Is it reasonable to seal a plywood panel with Shellac to keep moisture out and then use that panel with traditional RSG and/or gesso? From my research and experience it is common to simply size wooden panels with RSG first, and then continue to apply RSG gesso. However given the hygroscopic nature of both the wood and RSG, wouldn't sealing with Shellac first at least help reduce movement and other problems caused by moisture? The panel manufacturers I have been talking to in New York certainly encourage sealing panels with Shellac but the majority of their customers are working with acrylic and oils, not traditional gesso and egg tempera. What do you think?

    Thank you, I love this forum btw!


    Eli Bornowsky

  • Question asked 2019-03-12 15:01:32 ... Most recent comment 2019-03-15 15:43:16
    Rigid Supports Oil Paint Industrial and Non-Traditional Products Alkyd

    I'm considering using either PMMA or a composite panel for an oil painting (using alkyd medium). I expect the size to be around 100 by 70 cm, possibly a bit smaller. In order to keep the weight of the panels manageable, I don't plan on using PMMA thicker than 4 mm (the composite panel will be 3 mm). I understand that this should be cradled somehow on the back? Or would a solid frame with back supports suffice?

    On that note, is there a general rule for how large a panel can be, given its thickness, before it needs some sort of cradling?

  • Question asked 2019-03-14 00:55:45 ... Most recent comment 2019-03-15 01:24:15
    Drying Oils Oil Paint Pigments Technical Art History

    ​I'm wondering if the mechanism for oil paint becoming more transparent over time is well understood?

    More specifically, if I paint a layer of paint over another layer, will they both become more transparent at the same rate, or will the top layer become transparent more quickly?

    I know some pigments will fade more quickly than others, but for simplicity, let's make the pigments in both layers identical.

  • Question asked 2019-03-13 19:43:15 ... Most recent comment 2019-03-13 22:21:37
    Pigments Oil Paint

    ​Hi! I love Williamsburg Oils’ color they call Alizarin Orange but I’m confused about why its lightfastness rating is Fair, when the pigments it consists of are rated as Excellent by Gottsegen. It consists of PR 177 Anthraquinone and PY 83 Diarylide Yellow HR-70. Bound in alkali refined linseed. Both PR 177 and PY 83 are rated as having “excellent” lightfastness in oil by Mark David Gottsegen in his book. Who is correct?

    I typically use this color by itself in thin glazes but sometimes in tints with titanium white or mixed with other transparent warms like quinacridones.

  • Question asked 2019-03-10 10:16:02 ... Most recent comment 2019-03-10 21:18:12
    Chalk Flexible Supports Pastel

    I have tested some kraft paper (the brown one used for packing) and construction paper and concluded that the surface works really well for drawing, even better than some art papers. I tested them and it appears both have good pH, but I know that they will probably still deteriorate with time.

    I read in the Flexible Supports advice that paper can be attached to a rigid support to preserve it for longer, and wanted to make sure  whether this applies to all papers, including ones not strictly intended for artist use?

    My plan of securing them would be: attach the paper to an HDF or hardboard cut to a slightly bigger size using a heavy acrylic gel (or acrylic gel medium) spread on the board surface, remembering to press the paper so that there are no air bubbles/creases formed. I know that the paper will likely still discolor, but I don't mind that. Considering the durability of acrylic, I would expect the drawing to last indefinitely in the right conditions, since even though the paper would become brittle, the strength of the acrylic medium would hold it together. Can anyone knowledgeable about this subject comment? Should I be worried about pigment discoloration, if I plan to use lightfast pigments like charcoal, sanguine and white pastel?

  • Question asked 2019-03-08 12:53:00 ... Most recent comment 2019-03-08 14:46:10
    Animal Glue Art Conservation Topics

    I am looking for an archival glue for adhering wood to paper that dries fast. I am using small pieces of wood to make an armature for paper for a diorama. I had been using an archival hot glue but it seems too brittle and will not hold the individual pieces to the wooden box they are going in to.  

  • Question asked 2019-03-05 19:00:19 ... Most recent comment 2019-03-06 15:54:53
    Paint Additives

    ​ I'm trying to evaluate the degree of risk associated with inluding one frequently used colour bound in safflower oil (a white paint for example) in a palette where the rest of the colours are bound in linseed oil and the paintings are on rigid panels.  

    Your document on mediums states that paints bound in safflower oil yield a "slightly weaker film" than those bound in linseed oil.   I can see how this would be an issue when painting on stretched fabric where the paint needs to withstand flexing but is this less of an issue when painting on a rigid surface?    

    Secondly, colours are rarely used without being mixed with other colours. If only one of the paints on the palette contains safflower oil does that also reduce risk?  

  • Question asked 2019-02-25 12:14:22 ... Most recent comment 2019-02-25 21:50:34
    Rigid Supports

    ​My Mt. Athos friend has another question. 

    The icon workshop seals all sides of their wood panels with Lascaux Varnish (which I believe is B-72); 3 layers on front, 2 on back and sides.  They do this as the last step.  Is there a preference as to when sides and back get sealed (i.e. when the panel is first made, or when the painting is finished)?  And does B-72 protect against  humidity as well as an oil based paint?  



  • Question asked 2019-02-22 13:02:50 ... Most recent comment 2019-02-22 17:38:38
    Oil Paint

    ​Hi There, I'm a painter and am looking to incorporate spray paint into my paintings. I usually paint in acrylic first then oil and would like to be able to paint with an oil based spray paint in the upper layers of the canvas. Do you know what the longevity or archival nature of using a oil based spray paint or enamel might be? what changes or adhesion issues might i run into using a product like rustoleum? is it a big no-no? should I try using high quality oil paints via an airbrush instead? Thanks!

  • Question asked 2019-02-20 02:18:13 ... Most recent comment 2019-02-22 03:42:35
    Oil Paint Paint Mediums Alkyd Drying Oils

    Dear MITRA moderators,

    Due to my painting style, I need a medium that will enable me to blend my initial wet-in-wet oil layers the next day. Like many, back in the day I used the old painting medium mix of 1/3 each dammar varnish, linseed or stand oil, and artist's rectified turpentine. Needless to say, once I learned of the longevity pitfalls with dammar varnish, it has been in my rear view mirror. I also switched from turps to odorless mineral spirits. I do miss the "buttery feel" of how the paint moved when I used the old 1/3's mix.

    I started using walnut oil several years ago when I was told that it yellowed less than linseed products. When I learned that alkyd oil mediums are recommended for the greatest longevity, I tried one, but it dried way too fast for my technique, getting quite gummy both in the brush and on the panel before the end of my painting session. I then tried the walnut alkyd, which I greatly prefer over the other alkyd medium brand due to the slower drying time, but it also gets too gummy and isn't reliably blendable the next day. (I do mix a touch of OMS with the walnut alkyd, which works better than the straight product for me.)

    Additionally, with both the walnut oil medium and the walnut alkyd medium, I find each layer to be a weak paint film when dry to the touch or even "bone dry". I have read similar comments about walnut oil's weak paint film on other MITRA posts, though the manufacturer has assured me that it will get stronger with age. However, my periodically slightly vigorous application or removal technique when painting indirectly with subsequent layers has meant that sometimes I inadvertently bite into the previous layer, so I'm also looking to strengthen my painting medium. 

    Chemically, I know that walnut oil and stand oil should be compatible, but would it overly complicate the structure to put a few drops of stand oil in with my walnut alkyd medium – or at least the last couple of fatter paint layers? Are the benefits of alkyd oil painting mediums so great that it would outweigh any such complication, or would it be better to return to a slower-drying oil medium mixture – but without the dammar varnish? 

    I want to make painting fun again like it used to be! For me, this means paint that flows and moves, doesn't dry too quickly, and makes a strong paint film so that I don't have to worry about removing the previous layer when cleaning up the edge of a newly applied stroke. It also means that I can rest easy knowing that I have done my best to create works with the greatest chance for longevity.

    I appreciate any information or advice you can impart. Thanks very much!

  • Question asked 2019-02-20 11:53:31 ... Most recent comment 2019-02-21 13:38:18
    Rigid Supports

    ​Has anyone used Inner Glow panels?  Does the wood check or split or has it been properly seasoned?  thanks so much.

  • Question asked 2019-01-24 06:06:43 ... Most recent comment 2019-02-20 22:39:27
    Paint Making Watercolor Pigments

    ​Dear MITRA Moderators, 

    I want to create a three-layered paper piece based on the element of Earth. I'm doing a four-piece suite, one for each element, and am involving each element directly (for fire, I burned the edges of the paper), etc.

    I'm using a 300 lb paper for the first layer, and would like to use natural pigments including clay soil. I'll adhere a second layer (140lb paper) to the first with a brayer, using a product recommended to me by the art supply representative (Daniel Smith Transparent Watercolor Ground). I'd like to use natural pigments here, including clay soil and a homemade walnut stain. For the final paper layer, I'll adhere a thinner paper (I think it's 90 lb) and use watercolor pencils. I plan to distress the first and second paper layers respectively to expose the pigment underneath.

    Does this sound like a sound approach? Can you use regular clay from a yard or creek? Is homemade walnut stain ok to use, or would it be too acidic, etc? 

    Many thanks! I'm really excited about this project!

  • Question asked 2019-02-11 15:39:36 ... Most recent comment 2019-02-16 11:41:10
    Sizes and Adhesives Grounds / Priming Rigid Supports Flexible Supports

    ​Hello dear people from MITRA.

    I wanted to ask some questions regarding mounting on wood panels.

    1. Do you think that 9mm birch plywood is ok to use as a base for mounting  canvases, papers?  If not, what kind of wood do you think is better to use as a base for mounting?  

    2. Before mounting a canvas/paper to wood, do you think that wood should be sized with something? And if you do, with what kind of sizer? 

    3.When mounting a linen canvas/paper what kind of glue should i use? I have heard people using Golden Soft Gel as a glue for mounting canvases/papers , or some kind of PVA glue...? 

    4. Do you think that this practice of mounting canvas/paper on wood panel is archival? 

    Thank you

    Marko Karadjinovic

  • Question asked 2019-02-13 12:53:41 ... Most recent comment 2019-02-13 15:27:43

    ​If there an archival way to affix pastels?

  • Question asked 2019-01-30 12:33:30 ... Most recent comment 2019-02-11 15:25:44
    Oil Paint Pigments

    ​As I reach the end of my titanium white supply, I am revisiting the decision to again mix a 50-50 lead-titanium white for painting.

    Titanium white gives a greater opacity over time, but my understanding is that it creates a "softer" paint film.

    Lead carbonate white has less opacity, but creates a stronger, harder paint film.

    I mix them to hedge my bets with some of the good properties of both.

    As I now paint almost exclusively on 10 mm, honey combed, aluminum panels, which will not bend , expand, or stretch like stretched linen, how important is it to have a "strong" paint film?

    As I am now using a 25-75 walnut alkyd-OMS medium, is there enough strength and flexibility provided by the alkyd to eliminate the lead carbonate?

    I tryi to keep things simple and the paintings "permanent" and when there is an opportunity to do so, I question my methods and materials.

    Thanks for your help,


    PS   Not sure that I can do anything more to provide permanence in my paintings.   Painting on panels is a biggie.

  • Question asked 2019-02-10 05:29:14 ... Most recent comment 2019-02-10 15:12:52
    Grounds / Priming

    ​I am looking into using a gesso consisting of French marble dust, limestone powder, titanium dioxide pigment and plant-based binders (Methyl Cellulose).  Or one with just the limestone and methyl cellulose. (I am unsure of the ratios because the powders come premixed)

    I have a few questions:

    Are there any conserns to consider about any of the ingredients, soaking up, cracking, archival etc.?

    Does anyone have experience using a type of alternative gesso like these?

    The gesso will be used as a ground and primer for streched linen canvases, applying 2-3 coasts. 

    Reason for this type of ground: looking for a nontoxic enviro friendly option. An alternatve to acrylic, PVA or rabbit hide options.  

    thank you in advance for your time

  • Question asked 2019-02-06 17:36:32 ... Most recent comment 2019-02-10 11:14:43
    Art Conservation Topics Egg Tempera

    Hello Mitra,

    Among the questions the Mt. Athos iconographer sent me, what follows is the most vexing.  It is also very complicated.  His email explanation was very long, so I have extracted the main points below.  

    The Problem

    The workshop has a large icon production, each monk using same materials and procedure.  About 3 years ago some icons appeared "faded" (not sure if icons are literally losing pigment particles or pigments losing their color).  See images, attached.  On left, icon in good shape; right, icon with diminished color.   He says they appear worse in person.

    Mt. Athos Icons, 1.pngMt. Athos Icons, 2.pngMt. Athos Icons,3.png

    - The color change takes place within 3-6 months after completion. 

    - Does not occur on all icons

    - Occurs on both unvarnished and varnished icons.   

    - Occurs mostly on large icons.

    Materials & Methods of Workshop

    - Use Cedar Wood Panels

    - Traditional Gesso with 100-300 bloom strength glue

    - Use pigments that are, in his words, "dried out, old, cheap"

    - Use premade (by the monks) mixes of 6 to 8 pigments for flesh and other areas

    - 1 part egg to 1 part vinegar medium

    - Hard, tap water to thin paint

    - Would often thin tempered paint with water considerably

    - Finished with Lauscaux Acrylic Varnish

    - Very humid environment


    In an effort to solve the problem, they made the following changes:

    - Replaced all pigments with new colors from good companies

    - Simplified premixes of color to just 2 pigments (i.e. flesh = Iron Oxide Yellow from Schminck, Eisen Oxide Orange from Kremer)

    - No vinegar in medium

    - Replaced tap with distilled water

    - Not thinning tempered paint with water anymore

    Once they made the above changes, the problem decreased 80% but is not entirely gone.  

    My Comments

    I have a few comments on their practices:

    - Use a 450 bloom strength, 100% collagen glue in gesso.

    - If working with pigment pastes, be attentive to the potential for mold (i.e. if pastes are partly drying out & sitting for a while)

    - Pigment age isn't an issue (they don't become "old") unless they are (a) in a hydrated/semi-moist state (can cause mold), or (b) a fugitive color, which can be affected by UV light (work with ASTM Rated III colors).

    - A "cheap" pigment isn't necessarily bad, many earth colors are very inexpensive.  However important to buy from a reputable supplier of artists pigments that can give specifics (origin, lightfast rating, toxicity, etc). 

    - Complex premixes of color are fine.  However greater complexity  in a system = greater chance of problems, harder to diagnose source of problem.  Nonetheless, doesn't mean a complex system can't be successful. 

    - Mineral pigments are most stable.  

    - Vinegar can act as a preservative but it's acidity may affect some colors.  Better to nix vinegar and just start with fresh egg (as they are now doing).

    - Once paints tempered properly (correct ratio of yolk to pigment) can thin tempered paint with more water to affect working properties.   In fact, would be unnecessarily very limiting to work only with paint of all the same density.  

    However, if you significantly thin tempered paint with water, at some point the binder (egg yolk) is so dispersed, that it becomes necessary to add a drop or more yolk medium to paint. There isn't a precise formula for when more yolk is needed in very water-thinned paint, more of a feeling; i.e. when paint feels like watercolor instead of a bodied, egg-based paint, add bit more yolk to the paint. 

    Explanation for Changed Colors

    While I think the icon workshop could (or already has) improve some of their practices, none seem to explain the change in appearance of the icons.  I don't even understand what's happening to the color!  Given that some varnished icons faded as well, I don't think they could be literally losing pigment (as a varnish wouldn't permit that); it seems more likely pigments are losing color.

    The two things that strike me as potentially problematic are (a) the high humidity in their region, and (b) the cedar panels.  I was struck by the response to an earlier question I posed which mentioned VOCs emitting from cedar can affect metallic colors - might the VOCs be turning some pigments transparent?  If so, why some icons but not all - different wood & atmospheric conditions? 

    So I'm puzzled by his dilemma and welcome any ideas.  I also welcome response to my comments to the workshop to improve their practices.  


    Koo Schadler

  • Question asked 2019-02-02 13:17:56 ... Most recent comment 2019-02-06 17:37:35
    Rigid Supports

    My Mt. Athos correspondent says the monks work on cedar panels. I suspect they work on cedar because the wood is insect and rot resistent, but are there consequences to the resins in such a wood?  Cedar takes staining very readily; does this mean it's especially porous and thus more vulnerable to absorbing RH?  Any more thoughts on the pros and cons of cedar as a painting support, specifically cedar coated with traditional gesso?


    Koo Schadler

  • Question asked 2019-02-06 08:55:15 ... Most recent comment 2019-02-06 14:48:52
    Paint Mediums Solvents and Thinners Oil Paint

    ​One of my colleagues used to use Laropal K80 for making his own painting medium. This product, however, is replaced by Laropal A81 for some time. But using this new A81, the ratio laropal/white spirit seems off, it turns into a tough sticky substance. Does anybody here, know what the ratio should be, or how to avoid the gunk?


  • Question asked 2019-02-02 12:27:08 ... Most recent comment 2019-02-03 07:57:52
    Animal Glue Grounds / Priming


    I recently received an email from a monk living on Mt. Athos; he works in the Iconograpy department.  He has many question, including trying to address a recurring problem with their icons.  I'm in the process of editing his query to a manageable size.  Here is the first of several questions from him that I'd like to pose to MITRA:

    Is the most important thing in a gesso glue that it is genuine collagen and good quality, or that it has a high bloom strength?  We are currently using Lucas brand, bloom 100-110 and 180-200.  I understand that the recommendation for gesso is 450 bloom. So can RSG be good quality but also a lower bloom? 

    Thanks for helping me to help the Mt. Athos monks.

    Koo Schadler

  • Question asked 2019-01-30 22:50:10 ... Most recent comment 2019-01-30 23:22:22
    Oil Paint

    ​Maimeri makes a product called Eco Oil Medium. Looking up the SDS, it is 100% Dipropylene glycol (DPG), readily available from hobby cosmetic suppliers. It seems to have a good safety profile.  It sounds like it would replace the use of a drying oil as a medium, with lower viscosity (described by one user as watery). I might find the Eco Medium preferable if it doesn't cause yellowing or longer drying times, as oil mediums can.  Is anything known about adding dipropylene glycol to oil paint?  Should it be considered experimental?

  • Question asked 2019-01-29 18:43:38 ... Most recent comment 2019-01-29 21:10:40

    The only recommendation I have ever found for what to use as an isolation coat is a mixture of water and Golden soft gel gloss. Are there other products that make a good isolation coat, with or without mixing with water? I am interested in a brushed, not sprayed, application.

  • Question asked 2019-01-28 06:48:52 ... Most recent comment 2019-01-29 17:03:16

    I read in another post that "Alkyds dry quick to the touch, compared to oils, because of the long polyester polymeric chain component to them." ... but   

    "After this first drying step, they dry much like traditional oil paints, which is by auto-oxidation and cross-linking.  So, they dry to the touch faster, and can get ‘stiffer’ faster, compared to oil paints, because of the polymer component, but they eventually dry in a similar fashion to oil paints."

     The key advantage of alkyds then seems to be that they quickly provide a touch dry layer that can be painted over. However, am I correct in assuming that paintings done using alkyd paints and mediums still come under the recommneded 6 to 12 month drying time before varnsihing. 

  • Question asked 2019-01-24 08:10:00 ... Most recent comment 2019-01-25 07:31:19
    Grounds / Priming

    ​can I use oil primer over an old acrylic painting to then paint a new work in oils

  • Question asked 2018-11-07 14:46:31 ... Most recent comment 2019-01-25 00:30:05
    Acrylic Rigid Supports Art Conservation Topics


    I am working on a painting (acrylic) on heavy plywood (about 2cm thick). It is 48x48cm. I would like to frame it when it's finished. But I am worried about using screws. Is there a way to frame that painting without making holes in the back? Also, the whole picture should remain visible so I can't press its edges on the front against the frame... 

    Thanks a lot for your help.

    Best wishes.


  • Question asked 2018-08-12 05:50:43 ... Most recent comment 2019-01-24 04:44:57
    Environment Flexible Supports Storage Rigid Supports Oil Paint

    ​Dear MITRA moderators and community,

    First of all, thank you so much for your time and expertise. I really appreciate this valuable resource that you are providing.

    My question is about relative humidity, and its potential impact on artwork, particularly on oil paintings. I have read your very informative pdf about artwork storage and whatever else I could find here or elsewhere about the issue, but did not see specific information as to what specifically constitutes "wide swings" or fast changes in RH.  Would this be something really quite drastic, such as leaping from 35% to 85% in 30 minutes, or does the phrase refer to more numerically subtle conditions, such as 55% to 65% within 24 hours?

    Since late May or early June, I've been experiencing humidity issues in my rented studio space that I definitely did not have last summer. I have a combined thermometer/hygrometer there as well as in my home studio. At the start of this, I was experiencing high humidity levels in the rented space of 70-75%, and even discovered some brown drips down one of my interior walls!  

    My landlord has been very responsive, and after fixing an air duct leak that had caused the brown condensation drips, he purchased a small dehumidifier for me to use. I know to avoid "wide swings" or fast changes in humidity, so hopefully I stepped it down slowly enough at first. While I was initially pleased that the dehumidifier unit has manual settings and three fan speeds to facilitate a slow change, unfortunately it just can't maintain a steady humidity -- I am usually still getting 10 or more percentage point swing each day. The daily temperature has remainded constant -- 70-72F.

    The supportive landlord is now making several changes and improvements to the property, including sealing my two exterior brick walls from the outside, as well as underneath my concrete floor from the basement, which will all hopefully contribute to a more managed interior climate.  In the meantime, is a daily swing of 10% considered a "wide, fast spread"?  My target is to get it down to 50% RH, but after a spike, I am setting it for 60 then 55 in an attempt to walk it slowly back down again.

    I wonder if bringing the oil paintings back to my admittedly overcrowded home studio would be a better temporary storage solution until the landlord gets this under better control. I do have client and curator studio visits in the rental space, so moving the oils isn't the ideal solution for other reasons, but the longevity of my work is of greater importance to me. The paintings that are hung on the two exterior brick walls (unavoidable since it's not a cavernous space) have blueboard backings. The only deformations I have found are on some studies done on small, flat panels that have no cradling. (I have already spoken with the Ampersand representative on how to handle that issue.) I have both oils on stretched linen and oils on cradled Gessobord panel in the space, both finished and framed, as well as in progress. I also have works on paper (framed and unframed) and framed photography in the space.

    I appreciate any further specifics you can provide on what exactly a "wide, fast" humidity spread would be in 70-72F, and whether it would be better to safely pack up the paintings and bring them home for now.

    Thanks again!

  • Question asked 2019-01-17 15:25:23 ... Most recent comment 2019-01-19 18:37:32
    Matting, Framing, and Glazing Rigid Supports Oil Paint Art Conservation Topics

    ​I've been trying to come up with a better way to frame oil paintings on (solid, uncradled) wood panels. My current thought is: 

    1. Construct the frame to allow for the appropriate amount of room for expansion within the rabbet. Fill the voids on the sides of the panel with a polyethylene foam (e.g. EthaFoam, Volara, Cellu-Cushion). 

    2. Cut a large piece of polyethylene foam to fit behind the panel, filling the rabbet flush to the back of the frame.

    3. Screw a piece of 1/8" plywood to the back of the frame to hold everything in place. 

    Basically the panel would be surrounded, sides and back, with foam that would hold it firmly in place and keep it centered in the frame, while also not restraining the panel, so that it can move in response to changes in humidity. 

    Is this a sound approach? Is a polyethylene foam material like EthaFoam a good material for this application? 



  • Question asked 2019-01-18 19:13:47 ... Most recent comment 2019-01-18 19:35:41

    ​I applied an oil gilding, which is now perfectly dry.

    I've changed my mind, as I feel that some areas should be burnished to a high gloss. Can I apply red bole over this and water gold it on top of the matt gold of the oil gilding?

    Thank you 

  • Question asked 2018-11-01 12:15:10 ... Most recent comment 2019-01-18 12:30:54
    Drawing Materials

    Hello All

    I'm doing some metalpoint experiments and would welcome ideas and feedback.  

    Test Panel 1

    To test the value of marks made by 6 different metals on 18 different grounds (2 of which are paper: Plike and TerraStone).  Metal hardness will vary (pewter, gold, silver, copper, brass, nickel). 

    The goal is to see (a) which grounds produce the darkest marks, and (b) how the marks age (I've heard from various metalpoint artists that marks tarnish/age differently depending on ground).

    Test Panel 2

    Apply different metal points to a single ground to show variety of metal marks possible.   Metals to include: lead, lead-tin, pewter, zinc, pure silver, sterling silver, argentium silver, gold (22K, 18K, 14K), aluminum, copper, yellow brass, red brass, bronze, nickel, platinum, bismuth.  (I have all but zinc, bronze, bismuth - still working on those...).   For applicable metals I'll try both dead soft and half hard.

    Any ideas for other metals to try?

    Test Panel 3

    Test methods to speed up tarnishing using liver of sulpher, onions/garlic.

    Any other tarnishing tricks?

    Test Panel 4

    Add abrasive fillers to ground to see how fillers affect mark making. I'll use either generic house paint or student grade acrylic becasue I'm presuming I can add 10-20% fillers to them and they'll still bind well - yes?

    Among the materials I'm considering are....

        Titanium white

        Zinc white 

        large micron size pigments (lapis, natural earths, etc..)

        marble dust



        ground glass

        bone ash


    I realize some of theses substance (talc, gypsum) might be too soft  to affect marks, but I'd like to see.  Are there other wild and crazy substances I should try, just for the heck of it?  

    All comments are welcome.  Thanks, 



  • Question asked 2019-01-10 14:14:15 ... Most recent comment 2019-01-17 14:02:10
    Industrial and Non-Traditional Products

    ​After reviewing MITRA's rigid supports, I could not find any mention of ABS. A very accomplished and highly regarded oil painter (portraits/figurative) has recently begun using ABS for painting panels. The panel is lightly sanded and painted on directly with the oils. The painting surface is very smooth but has tooth after light sanding. How is ABS as a painting panel, if the thickness is similar to ACM thickness? Question- 1. ok to paint on directly with oils or casein or acrylic paint as one professional artist does? 2. ok if primer is used 1st? which primers? 3. ok to adhere canvas to? Here is a link that describes ABS very well. I had no idea that ABS is what Legos are made of!  "ABS is exceptionally resistant to chemical degradation, either by alkaline or acidic agents."

  • Question asked 2019-01-13 17:20:53 ... Most recent comment 2019-01-17 12:16:32
    Grounds / Priming Egg Tempera

    ​I just completed a metalpoint drawing on Golden Black Gesso.  I applied egg tempera (fairly densely painted, in multiple layers) on a portion of the drawing.  It's been my experience that egg tempera behaves best and ahderes longest on grounds with a lot of porosity, so that mechancial adhesion can take place; and for this reason I don't generally work on synthetic polymer grounds unless they have a lot of added solids and extra absorbency.  The egg tempera behaved pretty well a top the black gesso (a bit more sensitive to lifting, but not too much), so I'm wondering about the composition of the ground. Is Golden's black gesso high in solids, and/or considered more absorbent than regular acrylic gesso?  Has Golden (or anyone else) done testing of egg tempera on black gesso, to see how well it adheres in the long term?


    Koo Schadler 

  • Question asked 2019-01-11 07:48:39 ... Most recent comment 2019-01-13 20:17:27
    Storage Environment Studio Tools and Tips Scientific Analysis


    I have been thinking of asking this question for a long time, and have been reading about average and recommended humidity levels, but since my studio is in my apartment where i live, and we have radiators in every apartment in the building i find it very difficult to set humidity that is recommended...

    During the spring, summer and even some parts of autumn the humidity is usualy about 40-55 % . I have read that these are actually solid, ok humidity levels.

    But during the cold autumn days and during the whole winter, the city starts turning on the heating and the radiators begin working. 

    Temperature is usually set in whole building, so in every apartment is pretty much the same temperature, around 25°C . 

    Then the humidity levels drop  up to 12-22 % . 

    I was really worried when i saw that the humidity drops up to 12%. 

    I wanted to ask, do you think that low humidity like this represents a big danger to paintings( oil, acrylic, egg tempera) and watercolors, gouache paintings, also drawings....?  

    If it does, how can i fix this problem..? 

    Or are these strict rules meant for very old artworks that need extra museum care..? 

    I try to do best for my artworks, and to take care of them as much as i can, but whenever i start worrying that much, i cant help but to think how many old artworks survived in old houses, old studios, in some military storages during wars, and back  in ancient times when i believe artists didn't knew much, or maybe anything about humidity levels...? 

    Your answers are much appreciated!

    Thank you!

    Marko Karadjinovic

  • Question asked 2019-01-09 15:08:44 ... Most recent comment 2019-01-12 15:22:36
    Industrial and Non-Traditional Products

    ​The papers in question are made of calcium carbonate with a binder that makes it into a beautiful vellum smooth absorbent surface. I have used this paper with casein paint and casein as underpainting with subsequent alkyd/oil paint layers. I first adhere the unprimed mineral paper to sanded ACM panel using acrylic gel medium or lineco. Since paper is just calcium carbonate with a binder, wonder about the longevity of this paper? papers by Mitz or Yasutomo companies. Acid free. Mineral paper also handles well for acryl gouache.

  • Question asked 2019-01-10 08:22:53 ... Most recent comment 2019-01-12 08:22:33
    Pigments Mural Painting

    ​Does anyone know of a website or book that offers a complete list of pigments suitable for fresco?  The lists I find online are oriented towards historic fresco colors, or mention just a few modern colors.  I'm looking for a more comprehensive list.   


    Koo Schadler

  • Question asked 2019-01-10 16:20:52 ... Most recent comment 2019-01-11 04:25:07
    Art Conservation Topics Oil Paint Pigments Scientific Analysis

    ​Hi all,

    I was wondering if you had come across any issues with using Lamp Black (PBK6) in an allla-prima situation (no underpainting), when not mixed with other pigments or thinned with solvents? 

    I paint on ACM panels over a toothy clear gesso (silicia) which is much less absorbant than white gessos. I don't use zinc in my paints or in a primer/gesso.

    I use walnut oil to thin out my paint and I normally use Mars Black (PBk11) for my darkest blacks. I would like to try using Lamp Black instead as it should be a bit darker and have a longer drying time which I prefer.

    However I have read that it doesn't form very strong paint films and I am concerned that it would form a weak paint film when used on its own and may lead to cracking in the future?

    Has any studies found issues with Lamp Black in oil paintings when used in pure black areas?

    Thank you,

  • Question asked 2019-01-07 08:10:21 ... Most recent comment 2019-01-10 19:16:59
    Acrylic Paint Mediums Paint Additives

    ​Hello and happy new year to all!

    I have question about Acrylic mediums.

    I am painting with Liquitex Heavy Body and W&N Professional Acrylic colors. 

    I did a painting using Liquitex Gloss Medium/Varnish (Which people from Liquitex told me that it is best to use it as a medium) . 

    At the end, i wasnt happy with the results and i basically took other medium, LeFranc & Burgeois Acrylic Fluid Matte Medium (Since i liked the results more with it) and repainted the whole painting to something completely different.

    In this process i wanted so badly to make something that i will be happy with, that i didn't pay attention to what was on my pallette. So i accindetally mixed small amounts of previus medium (Liquitex Gloss medium/varnish) that was in some of acrylics, with this LeFranc Fluid Matte Medium. 

    I have heard that if i did something wrond it would be shown in few hours with acrylics? 

    I think that this is the painting that i will be happy with, so before i continue, i wanted to ask what do you think? 

    Did i make a big mistake in accidentally mixing small amounts of Liquitex Gloss Medium/Varnish with LeFranc Burgeois Fluid Matte Medium, because colors that were on pallette had small ammounts of both mediums in them...? 

    And is it a bad practice to switch from one medium to another on a single acrylic painting...? 

    Your answers would mean a lot!

    Kind regards.

    Marko Karadjinovic

  • Question asked 2018-12-27 21:19:28 ... Most recent comment 2019-01-10 18:22:41
    Rigid Supports Grounds / Priming

    ​I am currently working on birch plywood cradled panels that I have first sized on both sides with 2 coats of GAC 100, then applied thin layers of traditional glue gesso for painting in casein and oil. In a couple of the paintings I have seen a few areas of short parallel cracks coming through, and am considering adding a layer of thin fabric to the preparation process. Before I get in too deep with preparing a bunch of these panels, I'll appreciate some advice on 1.) the best material or materials to seal front and back of panel, and is the GAC 100 OK for this; 2.) best adhesive(s) for attaching fabric (I've used acrylic gloss medium for this in the past, but have had hide glue suggested to me as better).

    OR -is there a way to avoid the fabric step altogether, and simply prepare the wood surface well enough to accept the gesso? It seems like I've read various opinions on this and am now pretty confused! Thank you for your help.

  • Question asked 2019-01-09 11:54:24 ... Most recent comment 2019-01-09 16:43:11

    ​There seems to be a growing belief among painters and art teachers as to the 'miraculous' qualities of varnsihes based on Regalrez 1094. The most common belief seems to be that the full strength commercial varnsih can be safely applied when a painting is touch dry. Contrary to that, one vendror recommends the fingernail test which, in my testing takes anywhere from 2 to 4 minths to give the green light, depending on the number of layers of paint (overall thickness).  Another vendor recommends sticking to the tried and true 6 to 12 months.  To complicate this there is also some advice to thin a Regalrez varnsih with a solvent and use it as a retouch varnsih on touch dry paint.  Can you comment on this? Is a Regalrez varnsih differnt enough that the rues for varnsihing change? What are the risks of varnsihing too soon with a Regalrez varnsih?

  • Question asked 2018-12-21 17:24:39 ... Most recent comment 2019-01-01 12:07:54
    Drying Oils Oil Paint Solvents and Thinners

    ​I see recomendations for water miscible oil paint for ease of clean up and not using solvents.
    Can you please comment on them from the viewpoint of longevity?

    Ron Francis

  • Question asked 2018-11-28 12:33:33 ... Most recent comment 2018-12-31 16:02:26
    Oil Paint Solvents and Thinners

    ​Anyone know what these spots could be that are showing up on my oil painitng? I normally stain the canvas, but this time I opted to paint right on the white gesso. I did just clean my paint brushes, so worried maybe they werent all the way dry? I am using Geneva Oil paints and I used some Neo Megilp to cover the sky area. I can blend these out but then they show back up the next day. Any advice on how to remedy this is much appreciated! One picture is a close up of the problem area, the other is the whole painting, thought I find these mostly on the left side I have spoted a few in the lighter areas to the right. Screen Shot 2018-11-28 at 12.30.41 PM.png

    Screen Shot 2018-11-28 at 12.30.56 PM.png

  • Question asked 2018-12-26 17:34:07 ... Most recent comment 2018-12-26 19:42:57
    Oil Paint

    ​Attached are 2 photos. The first is my painting showing buckling. At first, it wasn't this bad. The canvas is Raphael zinc free on a professional art panel from NY Central art supply. The bucking started almost immediately after I finished the painting. The second is the product I used to fix the edges. Ultimately, it didn't work. The buckling has gotten worse even beyond the parts I fixed. Why could this have happened and how can I fix it so the integrity of the painting is restored? C9765112-BB82-43E4-BBF3-DEE492953D7F.jpeg B187BCB1-8686-4F96-BA7D-A0A049E40062.jpeg

  • Question asked 2018-12-25 16:26:08 ... Most recent comment 2018-12-25 18:31:20

    ​My cousin did a pair of acrylic paintings for my mother for Christmas, and wrapped the canvases with wrapping paper, with no intermediary layer (yeah, I know... yikes). Unsurprisingly, the paper stuck to the paint, particularly near the edges. I know acrylic films have a glass transition temperature that is pretty close to room temperature, and therefor there's always a chance that wrapping material will stick, even if the paint is well-cured. 

    I've sent my cousin a link to where she can purchase glassine paper, but in the meantime, I'd like to take a shot at salvaging these paintings, if it's possible. This isn't the sort of thing that my mother or cousin would hire a professional to do--if they get ruined, then so be it. My cousin says she will repaint them, if necessary. 

    So, conservators: if you were going to try to remove paper that is stuck to the surface of an (unvarnished, and also unsealed) acrylic painting, how would you go about doing it? Swab with some sort of solvent? Water? Something else?

    Thanks! And Happy Holidays!  :)

  • Question asked 2016-11-07 22:12:01 ... Most recent comment 2018-12-21 21:51:34
    Technical Art History Art Conservation Topics
    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 2018-12-12 08:24:59 ... Most recent comment 2018-12-16 18:20:22
    Drawing Materials Oil Paint Pencil

    ​I have seen people suggest using a kneadable eraser to lighten their drawings before painting over the top in oil paint, in a similar way to dusting off excess charcoal.
    I would be concerned that the eraser could leave some residue.
    Can I have your thoughts on this?

    Ron Francis

  • Question asked 2018-12-16 08:21:42 ... Most recent comment 2018-12-16 12:55:46
    Acrylic Alkyd Art Conservation Topics Handling and Transportation Paint Mediums Oil Paint Pigments Scientific Analysis Storage

    ​How important is a climate controlled vehicle for transporting oil and acrylic paintings? 

  • Question asked 2018-12-15 16:34:01 ... Most recent comment 2018-12-15 20:28:42
    Drawing Materials

    ​Hi all,

    I have large 30 X 22 inch sheets of new Canford Cardstock 300 gsm acid + lignen free paper that has areas of waviness / buckling throughout the paper.  These papers are new and have no drawings on them.  I am looking for a solution to flatten the paper back out if this is possible?  There are no creases, just curvy waves.  Any help would be greatly appreciated.  


  • Question asked 2018-12-08 05:32:27 ... Most recent comment 2018-12-08 14:50:33
    Flexible Supports Gouache Drawing Materials Pencil Watercolor


    As well as a lot of artists know, there are those moments of inspiration when we grab something that we have and express what needs to be expressed, not really thinking about technique, compatibillity of materials and so on...

    Basically we do what me must, and worry afterwords. :) 

    One of those moments for me was recently, when i did graphite drawing on Fabriano Unica Paper (which is 250 gr paper made of 50 % cotton and ideal for printmaking, graphite,charcoal) and painted over that with Gouache. 

    Is it a problem to use water media over graphite and on paper that is not best suited for it, but rather for dry techniques, but it is 250 gr paper and is Acid Free ofcourse? 

    Thank you!

    Marko Karadjinovic

  • Question asked 2018-11-19 19:27:52 ... Most recent comment 2018-12-08 13:39:54
    Oil Paint Other

    ​I am finding that after a period of about 1 year or more, surfaces where I have applied very thick areas of white oil paint have brown oil spots, as if the oil in the paint is seeping to the top. This may be due to the low quality of paint I’m using: Winton - or perhaps the kind of white: Titanium. In these cases I have not mixed any mediums into the paint. What is the cause, and can it be repaired? Can I simply paint over the surface with a higher quality white, and will that last?

  • Question asked 2018-12-03 16:43:49 ... Most recent comment 2018-12-03 16:30:00
    Egg Tempera


    Can you advise if I am able to frame egg tempera paintings done on gesso panels behind glass within 2-3 weeks of finishing?  Ideally, I would like the works to cure for a few months before framing but due to time constraints, I may have to frame earlier.  I have read the post on glazing ET works previously mentioned on this forum, so am aware of the need for separators etc - but wanted to check whether there would be any unacceptable issues with efflorescence/mould if framing is done this early - & whether the egg is particularly fragile at this stage.  Many thanks.  Zarina

  • Question asked 2018-12-01 15:09:46 ... Most recent comment 2018-12-01 21:24:38
    Oil Paint Gilding


    I want to try using gold/silver leaf with oil painting (the composite kind, not the real kind), and I was wondering how I should do it? I've used it with acrylic before and just gilded over top of the paint, but my understanding is that you shouldn't gild over oil paint because it takes an extremely long time to try. 

    Would it be best to guild the panel first after priming, and then seal it (with what?) and then paint over it?

    I was going to try this approach:

    1. Size panel with GAC 100

    2. Prime panel with acrylic gesso or oil ground and let dry for a few weeks if oil, for 1 week if acrylic

    3. Draw out composition with watercolour pencil and then gild the panel where I want the gilding with Speedballs liquid size

    4. Seal it with speedballs liquid sealer

    5. Let dry for a day

    6. Begin painting

  • Question asked 2018-11-23 13:28:45 ... Most recent comment 2018-11-26 16:12:11
    Gouache Watercolor Ink Pencil Varnishes Matting, Framing, and Glazing


    I would like to ask multiple questions, since it is about mixing gouache with other techniques.

    1. Since many say that gouache is basically opaque watercolor (with more gum arabic binder?), is there any proper way to use it with watercolor? For example, is it ok to paint first layers with watercolor and then to finish the painting with gouache? When switching from watercolor to gouache on the same painting, is there any right way to do it, or i just simply paint with gouache over watercolor? 

    And is it possible to switch process, to glaze with watercolor over opaque gouache? 

    2. When doing underpainting with Ink, and then painting over that with gouache, which type of Ink is best suited for mixing ink wash technique with gouache technique? And how much can Ink be diluted with destiled water? 

    examples of this technique:

    3. When doing a drawing with black chalk or graphite, and then doing wash with brown or black ink, and then painting with gouache on top of that, is there a right procedure to do it, or i just simply switch from one technique to another as mentioned above?  And, what type of fixative is best suited for preserving a chalk or graphite drawing beneath ink, and gouache? 

    examples of this techniqe:

    4. When switching the process and doing watercolor underpainting, gouache painting, and then adding chalk, graphite in the final stage of painting, is there some sort of varnish or fixative that is best suited, so that graphite/chalk would not be smeared over the painting? 

    example of this technique (Graphite (Chalk?) was used in shadows and lines, in the final stage of the painting )):

    5. Can gouache be mixed with acrylic painting?

    6. How should gouache, or mixed media (ink,gouache,graphite) be framed?   

    Thank you in advance!

    Kind regards.

    Marko Karadjinovic

  • Question asked 2018-11-25 09:24:23 ... Most recent comment 2018-11-26 12:39:49
    Oil Paint Alkyd Grounds / Priming Health and Safety Rigid Supports Sizes and Adhesives Art Conservation Topics


    I am re-reading my post of February 19, 2018,, and all the responses below it. As you know, I am hoping to work without toxins throughout my processes. I am seeking to know: can I create a stable painting without them? After laying out my specific questions for you to consider, I will describe my proposed modified approach, based on the answers you have given thus far.

    Specific Questions:

    Although lead white would add strength to the canvas, will the combination of my various processes create a more than adequate archival stability for my paintings over the centuries?


    Can the rigid support (cradled panel) and the alkyd nature of my titanium white compensate for lead white usage in the ground and throughout my painting?

    Can a traditional wet imprimatura compensate for the greater absorption of Golden Acrylic Gesso Ground? (I hope so - it seems to do a perfect job of it – performing for the artist during the process just as well as chalk gesso does – with perfect absorption level for the richer glaze layer and excellent surface flow for the subsequent lean paint).

    Proposed Process:

    1.  Size a 16 oz. tightly woven raw canvas one side on the topside while fabric is flat on table. I prefer Gamblin PVA, for reasons already stated in a previous reply.  Snap the fabric when wet to work out any wrinkles. Let dry a day.
    2. Evenly stretch canvas over a birch cradled panel, with the weft direction being vertical for maximum long-term support. Use non-rusting strong thumbtacks for easy potential conservation adjustments if ever required.
    3. Rewet the stretched canvas after stretching with PVA if there are still any wrinkles to facilitate the pullout of the fabric. Let sit a day.
    4. Hand rub and sand five coats of Golden Acrylic Gesso Ground, slightly diluted for smooth application.
    5. Allow to cure over several days.
    6. With Gamblin Solvent Free Fluid, dilute Gamblin FastMatte Alkyd Safflower Oil Foundation paint (mostly Burnt Sienna) no more than 25%. Rub on a high paint spread imprimatura-priming glaze with a cloth.
    7. Into the wet glaze, drop an undiluted foundational layer (grisaille) using Gamblin FastMatte Titanium White and Burnt Sienna and Ultramarine Blue (mixed to the same colour as Burnt Umber). Let dry several days.
    8. With virtually undiluted Gamblin FastMatte paints, add another foundational layer (Velatura). Let dry several days.
    9. Add several layers, several days apart, each starting with a glaze or scumble of the same paints diluted with no more than 25% Gamblin Solvent Free Fluid, with high paint spread. Then modify the glaze with additions of slightly diluted paint, or in white areas, undiluted paint.      


    Gamblin FastMatte Alkyd Safflower Oil Paints:

    • Titanium White
    • Burnt Sienna (in foundations)
    • Quinacridone Red
    • Hansa Yellow (in foundations)
    • Ultramarine Blue
    • Phthalo Blue
    • Red Transparent Earth (in glazing applications) 

    Rembrandt Oil Paints

    • Transparent Yellow (in glazing applications)

    I am looking forward to your answers. Thanks so much for all you do and for your clarifications here.

    Kathy Marlene Bailey

  • Question asked 2018-11-22 11:12:23 ... Most recent comment 2018-11-23 15:21:54

    I have to varnish a big oil painting (200x370 cm), and I do not have a lot of experience with varnishing oilpaintings, to be honest. So I have some questions that I hope you guys can help me with.

    -It will take quite some time to get the whole surface varnished, right? What varnish would give me enough time to work? (I'll ask two students to help me).
    At the same time, the work is hanging in a canteen, so fumes should be not overwhelming for too long :-/.

    -And how much varnish do I need for such a surface? The paint itself is rather smooth, but I doubt if 1 liter would be enough.

    -And third, and last: we have to do this with the work standing, so not laying flat. How do I avoid dripping?

    Thanks in advance,


  • Question asked 2018-11-21 16:26:35 ... Most recent comment 2018-11-21 16:54:54

    ​New to Mitra.  So I am not sure how to use the search option.

    How do I remove old damar varnish?  I tried using Turpentine, but it isn't removing the damar.  

  • Question asked 2018-11-12 21:44:45 ... Most recent comment 2018-11-20 15:24:48
    Drawing Materials

    I would like to protect large charcoal drawings well enough to frame without glass (in a recessed frame). Not ideal, but the glass is an expensive and unwanted barrier. Perhaps Lascaux fix, multiple coats, then another acrylic sealer on top? Wax on top? Other artists must have solved this problem for large scale drawings?​ I have read everything under the category to date.

  • Question asked 2018-11-14 09:05:36 ... Most recent comment 2018-11-14 08:31:00
    Solvents and Thinners Oil Paint


    I'd like to ask about possible differencies between various odorless/low odor solvents. I use Winsor&Newton Sansodor for cleaning brushes, sometimes to make mediums or dilute paint. I have some amount left but soon I will have to buy more. The price for 1 liter can in the shop from which I usually buy the stuff is cca. 32 Euro. That is not really cheap. Recently, I looked at Kremer pigmente and also asked them about their alternative and I was told, that it is Shellsol T. 1 l can is for 5,36 Euro. That is striking difference. So I've been wondering what is the difference between them - or between odorless solvents in general. I looked into MSDS sheets of four odorless solvents:

    W&N Sansodor (

    distillates (petroleum), hydrotreated light, CAS-No.: 64742-80-9, EC No.: 927-632-8

    Schmincke Diluent N (

    Substance 1: hydrocarbons, C4-, butadien-free: 50 - 100 %, CAS: 93685-81-5, REACH: 01-2119490725-xxx

    Substance 2: hydrocarbons, C10-C12, isoalkanes, <2% aromatics: 10 - 25 %, CAS: 64741-65-7, REACH: 01-2119471991-xxxx

    Gamblin Gamsol (

    Naphtha (petroleum), hydrotreated heavy CAS: 64742-48-9

    Kremer Shellsol T (

    Hydrocarbons, C11-C12, Isoalkanes, < 2 %, 100 %, CAS-Nr not stated, EINECS-Nr: 918-167-1

    If I consider just the term "odorless/low odor solvents", all these things should perform the same. But then I don't understand the difference in price. I guess, that various CAS numbers mean, that the composition is somewhat different in each case. Shellsol T is six times cheaper than Sansodor and Diluent N, but I suppose that doesn't mean that it is inferior product (and also I suppose Kremer wouldn't offer some sort of cheap "trash"). 

    Can you explain meaning of those terms like hydrtretaed heavy, hydrotreated light, C11 (I saw msds of various solvents containing a range of these, like C11-C12, C9-C14, etc.)? How does it affect the nature and performance of solvent? Also, do you have any experience with Shellsol T in particular? What should I expect from it? If it performs that same as e.g. Sansodor there is no reason for me to go for Sansodor, which is six times more expensive.



  • Question asked 2018-11-11 16:22:57 ... Most recent comment 2018-11-11 16:20:00

    ​Wondering about the use of amber mediums and varnish in oil painting. Benefits, drawbacks? It is very expensive and Blockx is the only company that makes it at present.

  • Question asked 2018-11-09 13:03:06 ... Most recent comment 2018-11-09 13:00:00
    Drying Oils Paint Additives Scientific Analysis


    Could someone tell me about why walnut oil has a slippery feel compared to other drying oils? Someone mentioned it's probably because of a higher glycerin content in walnut oil?

    I have read someone else say that it's not recommended to all glycerin to oil paints though as it will interfere with the drying process?

    Any thoughts on this?


  • Question asked 2018-11-09 11:32:04 ... Most recent comment 2018-11-09 10:50:00
    Grounds / Priming


      I'm trying to better understand my options for priming panels for oil painting and the pros and cons of each system. I was hoping someone could enlighten me with regards to acrylic primer. 

    1. As I understand there are three mechanisms that enable adhesion of a new layer in a painting:   a) chemical bonding, b) absorption (wetting of the existing surface by the applied layer), and c) mechanical bonding (interlocking with rough/textured areas). Is this accurate?   

    2. When applying the first layer of oil paint over an acrylic primer I assume that there will be no chemical bonding ? 

    3. Acrylic grounds have calcium carbonate added to promote mechanical bonding. Is this intended to be the primary adhesion mechanism between the first layer of oil paint and the acrylic primer?

    4. I've noticed that some brands of acrylic primer tend to be less absorbant than others - as evidenced by less sinking in of the first layer of piant. Also, "non-absorbant" acrylic primer has appeared on the market. It begs the question, what role does absorption play in the bonding of oil paint to acrylic primer?  Can too much absorption rob the oil paint of binder? Can too little absorption limit adhesion? 

    Thanks in advance and I just want to say that this website and forum is a greatly appreciated resource! 

  • Question asked 2018-11-09 00:41:06 ... Most recent comment 2018-11-09 00:35:00
    Oil Paint

    ​I asked about Bitumen/Asphaltum/Gilsonite at a painting techniques FB group. But, some warned that it is prone to cracking and fading in glazes. Although several manufacturers have paints named "asphaltum or bitumen" in their lineup ,they are NOT the traditional Nbk6 pigment but are various blends. One paint I bought was too reddish. The pigment alone is available from Natural Pigments and Kama pigments as gilsonite. The only oil paint I can find with solely Nbk6 bitumen is Maimeri Artisti. I would like to use this neutral transparent brown for glazing. But what about the fear of fading, cracking or some say darkening?

  • Question asked 2018-11-05 16:28:29 ... Most recent comment 2018-11-05 16:23:00
    Paint Additives Oil Paint Scientific Analysis

    ​Hello all,

    I was just reading an article from the UK art supplier (and manufacturer) about their own professional oil paint range:

    In the article they show an example of the proportion or ingredients used and I was suprised to discover that instead of using Aluminium Sterate they use Magnesium Sterate. I have not heard of this before.. would I be correct in thinking it would work similarly to Aluminium Sterate but have a drying action?

    I find their paints well pigmented, and good value for money, but too stiff and fast drying in some pigments for my personal tastes.

  • Question asked 2018-11-04 14:51:07 ... Most recent comment 2018-11-04 14:32:00
    Art Conservation Topics Solvents and Thinners Pigments

    I am currently working on a project in which I crush fruits and vegetables on Hahnemuhle cotton paper using a cylindrical engraving press. As the plants are emptied of 95% of their water in one pressure the color remains on the paper, it does not yellow for the moment, so I keep my print in the dark.

    I would like to protect the color of crushed plants from sunlight, UV ... would you have an idea of ​​invisible lacquer, or colorless and matte varnish that I can pass on the plants without damaging or altering the paper?

    I also thought of sticking a very fine paper, type rice paper 20 grams, on my print using rice glue or vegetable glue, to protect the plants (so they do not flake) and also protect them from light. When I do this the rice paper becomes almost invisible, I think that if on this paper I apply a layer of varnish to protect the colors from UV it would work, but what do you think?

    I don't know what to use, do you have any idea ?

    I have to find a solution to show the piece in February at an exhibition and I would like the colors of the fruits to be preserved  during the exhibition.

    Thank you for your help

  • Question asked 2018-11-01 15:40:25 ... Most recent comment 2018-11-01 15:29:00
    Varnishes Acrylic Art Conservation Topics

    ​I have a question about those paintings from artist Robert Vickery , that were done with acrylics. I have read that he used Liquitex colors, but what i am really interested is does anyone know with what type of varnish did he varnish those acrylic paintings, how those paintings look today? And are conservators able to remove this varnish and to clean the paintings without harming the acrylic beneath? 

    Thank you!

    Marko Karadjinovic

  • Question asked 2018-10-31 23:25:40 ... Most recent comment 2018-10-31 23:23:00
    Oil Paint Pigments


    Are there likely to be similar issues with PW7 in oil as there is with PW4?

    Many thanks.

  • Question asked 2018-10-31 19:47:55 ... Most recent comment 2018-10-31 19:47:00


  • Question asked 2018-10-31 17:09:20 ... Most recent comment 2018-10-31 17:07:00
    Sizes and Adhesives

    ​While getting ready for an upcoming show, I glued labels to the canvas backs of six of my works with fish glue. I like this glue because it is really tacky, dries fast and is reversible. To my utter horror I noticed that there is now a visible elevation the size of the label on the front of each picture. The paintings are oil on store prepped canvas. I did not add another layer of gesso before painting. Can I safely soak off the label on the back and perhaps dampen the unaffected area, or should I leave it alone and hope they don't get rejected. Any advise would be very much appreciated.

  • Question asked 2018-10-29 12:12:45 ... Most recent comment 2018-10-29 11:59:00
    Varnishes Oil Paint

    Couple of years ago i have heard about this practice that is ok to put a coat of Retouch Varnish over a painting after a month/two months and then after a year-year and a half to put a final varnish on top of that.  

    I heard that is especially ok to put retouch varnish  if the one needs to have a exhibtion, or has done commission and doesn't have year-two years time to let the painting dry.

    Year ago i have contacted few companies and asked about this, and got the answer that is totally ok to put retouch varnish after a month/two months and after a year-year and a half to put final varnish on top of that, and that i don't have to remove the retouch varnish before applying the final one.

    Also i have read that some conservators/restorators disagree, and that they think that the retouch varnish should be avoided, and that is best to put just a final varnish on a painting. If one needs to put a retouch varnish, then when he wants to put the final one should actually remove the retouch varnish before that??

    What are your thoughts about this and what do you think is the best way to varnish a painting, and how to protect it if one doesn't have enough time to let it stay unvarnished for a year-two years?

    Thank you in advance!

    All the best!

    Marko Karadjinovic  

  • Question asked 2018-10-29 11:22:31 ... Most recent comment 2018-10-29 10:39:00
    Paint Mediums Oil Paint Solvents and Thinners

    ​Hello! I have a few questions regarding oil mediums.

    1. I have done some of my paintings with oil medium that has Venetian turpentine in it. The formulation of this medium is one part of stand oil, one part of Venetian turpentine (Schmincke Natural balsam/larch turpentine) and two parts of turpentine ( Lefranc & Bourgeois rectified turpentine) . I have read that Venetian Turp/Balsam is not that recommended, but at the time i didnt know, so i did some very important paintings with this medium. What are your thoughts about this medium? I was very carefull about layers ( fat over lean) Do you think that these paintings will be ok, even if i did them with this medium? 

    2. I was also using Winsor and Newton Liquin Original medium.

    What are your thoughts about this medium, do you think this is good archival medium to use?

    And is it really true that you dont have to be that careful about "fat over lean" rule with W&N Liquin original? I always try to be careful about layers even with this medium. 

    I wanted to ask is there some substance that can be added to Liquin as a thinner, some solvent, because i paint in several layers? Or i should just use less Liquin medium in first layer and then add medium as i build up the painting? 

    Also i have combined two Liquin mediums on one painting. 

    I used Liquin original for first layers and then used Liquin Fine Detail for finishing layer. I have contacted W&N about this and they have told me that is totally ok to combine those two mediums, i just have to keep in mind "fat over lean" rule when i am combining them? What are your thought about this? 

    3. In museums there are some paintings that stood the test of time, and these artists did scumbling techniques, and glazes, and it really seems that they sometimes didnt care that much about "fat over lean" rule, and still it looks great. Do you think that we should maybe try to some extent to apply these rules, but not to be very precise and that concerned about it?  

    4. And i wanted to ask what types of oil mediums were least changed through time, and prooved to conservators/restorators as most stable? 

    I have heard that these were the ones which were more basic (stand oil + turpentine, or white spirit, or something like that). 

    What are your  advices about medium choice and what is the best way to  paint in layers? 

    Thank you for time and efforts!

    All the best!

    Marko Karadjinovic 

  • Question asked 2018-10-29 10:05:58 ... Most recent comment 2018-10-29 09:38:00

    ​I'm reading a 19th century Portuguese treatise on gilding. The master gilder that wrote it was called Francisco Liberato Telles de Castro da Silva. He was in charge of the restoration of the gilded woodcarvings of the church of Madredeus, in Lisbon.

    He advocates a recipe for the red bole that puzzles me:

    1kg Armenian red bole + between 120-150g of graphite powder + between 120-130g of sanguine hematite. This mix should be ground in pure water (and allowed to dry afterwards? The original text isn't clear on this), then mixed with a spoonful of olive oil and ground again. Just before use, this mix should be ground with a weak solution of rabbit skin glue and another spoonful of olive oil.

    I have two questions:

    If the original mix is allowed to dry before adding the olive oil (as the text strongly suggests) then a spoonful wouldn't be enough to wet the bole - so perhaps he didn't mean to fully dry but just to allow some of the water to evaporate, so the oil could be added to the thickened paste.

    Could this very small amount of olive oil be there just as a plasticizer? Wouldn't the fact that olive oil is non-siccative create problems with the drying of the mordant and also with the burnishing? On the other hand, I know that the most beautiful burnishing is achieved when the bole is just before fully dry (a few hours after, not a few weeks after)... maybe the small amount of olive oil replaces that necessary small amount of humidity, allowing top level burnishing to be done after all the water in the bole evaporated?

    Many thanks!


  • Question asked 2018-10-24 09:18:36 ... Most recent comment 2018-10-24 11:18:36
    Varnishes Acrylic

    ​Hello! I am new at the forum, i am very glad to be here. I am painting mostly with oils, egg tempera, but i also do paintings with acrylic.  I have a question about varnishing acrylic painting. Recently i bought Royal Talens Amsterdam Acrylic Satin Varnish and tested on one piece, and it looks really good. This is removable varnish, based on white spirit. I contacted Royal Talens also, and they told me that i dont need isolation coat because this is removable varnish based on white spirit, and it can be removed with the same solvent. My question is what do you think about these types of varnishes, and do you think it is a good practice to varnish acrylic paintings with them? The composition of this varnish is : Acrylic resin, white spirit, turpentine oil, matting agent (silica). Thank you

  • Question asked 2018-10-19 22:27:58 ... Most recent comment 2018-10-23 10:52:51
    Varnishes Oil Paint


    I was wondering if the edges of a painting should be varnished as well, or just the front of it? I paint the edges too so I figure I should varnish it but I wanted to seek professional opinions here. 

  • Question asked 2018-10-18 17:09:14 ... Most recent comment 2018-10-22 17:37:04
    Oil Paint Paint Mediums Drying Oils

    ​Ralph Mayer speculates that, because sun thickened oil is partly oxidised, it's adhesive proberties may be compromised to some extent.
    Do you know if this has been tested at all?

  • Question asked 2018-10-14 09:15:37 ... Most recent comment 2018-10-19 14:55:07
    Egg Tempera

    I have a painter friend who wants to isolate every layer of tempera she applies because she vigorously works each new layer yet doesn't want to affect underlying ones.  She wants to work in a similar vein to the English painter Nina Murdoch, whose working method is described as egg tempera alternating with varnish layers.  My friend wrote Murdoch to ask what she uses as a varnish but did not get a reply. I've read catalogs that describe Murdoch's work -

    One image shows a very high gloss, saturated surface – so I am puzzled what Murdoch could be using to achieve her working method and high gloss, but which keeps her work in the realm of "Egg Tempera".  (Of course I realize that artists' descriptions of their work, catalog captions, even museum labels are not always complete or completely accurate). 

    The catalog also mentions Murdoch's favored glazing medium recently went out of production; coincidentally my friend noted Sennelier's egg tempera glazing medium has been discontinued – could that be Murdoch's secret formula?  We don't know. I couldn't find Sennelier's glazing medium ingredients but their binding medium is made from egg, oil and gum Arabic.  I would rather such a medium not be described as "Egg Tempera"; I think it would be more clarifying to call it Tempera Grassa or egg/oil emulsion - but I realize I have no say in the matter. :-)

    I've wondered how the tubed egg temperas (which are in fact tempera grassas) by Zecchi, Sennelier, Rowney, etc are made - they can't use a yolk in its entirety as the paint would putrefy.  Do you know how they do it?

    Back to Murdoch's work, and my friend who's trying to understand it; she also prefers the more saturated, rich look of varnished tempera.   I have told her that, while alternating multiple layers of ET and some sort of water insoluble isolator is potentially quite problematic, I believe there are reasonably durable ways to isolate a final tempera layer and then varnish it.   


    Any thoughts on the above are welcome.

    Koo Schadler 

  • Question asked 2018-10-18 08:46:32 ... Most recent comment 2018-10-18 14:34:44
    Oil Paint


    I got this question from a student of mine. He wants to paint with oils on top of a inkjet print. My concern is that those inks might bleed into the oilpaint. Does anyone have experience with this?

  • Question asked 2018-10-09 00:44:21 ... Most recent comment 2018-10-18 11:08:46
    Oil Paint Alkyd Industrial and Non-Traditional Products

    ​I want to try adding glitter to some paintings of mine, but I'm wondering how I can do it properly with oil paint?

    I found that using Galkyd Lite by Gambin produces the least yellow tinted colour shift, and holds the glitter in perfectly so none flakes off. However I don't know if this could later be an issue due to either the alkyd yellowing (will it yellow?), or the fact that a layer of alkyd is sitting on top of a layer of oil paint. 

    What issues could I face here, and are there any tests I could conduct to see if it will last? I plan to sell the work so I want it to be high quality. 

  • Question asked 2018-10-10 06:29:40 ... Most recent comment 2018-10-17 14:26:25
    Animal Glue Art Conservation Topics Gouache Sizes and Adhesives Scientific Analysis Technical Art History Watercolor

    ​hi there, egon schiele used watercolour and gouache on different similie japanese papers / fake vellums & brown wrapping paper. did he size this wrapping paper to hold the paint or was the paper made in 1910 heavily sized to avoid seepage? either way is there a paper out there today that is similar to the paper he used? it is hard to find tinted papers for this medium. i have tried sizing my own papers with rabbit skin glue & gelatine, using coloured washses, kraft legion stonehenge paper and strathmore tan for mixed media (none have the same affect as schiele - his colours stand on the paper - not absorbent). apparently he use strathmore japan paper produced by mohawk fine papers. i have contacted both companies and both have directed me here. i have also contacted dr. jane kallir, the world's leading egon schiele scholar. i have also tried wetcanvas. does anyone know if his works have been under conservation. can anyone help? thanks

  • Question asked 2018-09-27 15:20:04 ... Most recent comment 2018-10-17 13:47:58

    I am working on reconstructing a Fayum mummy portrait, and a few sources I've read have mentioned methods that might have been used to make the wax easier to paint with. There's a small section in "Ancient Egyptian Materials and Technology" about "punic wax" that suggests beeswax was possibly saponified to make it water soluble. Do you know if that theory is plausible or have you tried painting with punic wax?

  • Question asked 2018-10-16 12:41:07 ... Most recent comment 2018-10-16 19:59:38
    Oil Paint Rigid Supports Flexible Supports Art Conservation Topics

    ​I was wondering if there's any benfit to using a layer of alkyd resin like Galkyd to help seal a painting? Will it help reduce moisture absorbtion? 

    I would apply it as the last step before painting, so my process would be: size wood panel using gac 100 x2 layers, adhere fabric to the panel with beva film, size fabric using gac 100 x 2, gesso or oil ground layer x2, and then 1 layer Galkyd and Gamsol 1:1 ratio to cover that.  I would be coating the entire panel front and back, including edges. 

    Is this overkill or is this a good way to do it? I just want to get a smooth and as warp resistant panel as possible. I'm using the cotton canvas overlay so that if the panel is ever damage the painting can be taken off, instead of having it painted right onto the wood.  

  • Question asked 2018-10-13 16:00:03 ... Most recent comment 2018-10-16 07:53:35
    Egg Tempera

    Several years ago, when testing isolators for egg tempera, someone (a materials expert) recommended Golden's GAC 500 and Acrylic Gel Medium as isolators.  Being water-based, I was skeptical they could be applied without disturbing a relatively new egg tempera painting, but in fact they went on fine and worked well.  I haven't used them since but suggest them to students as possible isolators (preferably with more testing). 

    Recently another materials expert told me that using GAC 500 as an isolator could prove problematic as it would create a completely unbreathable layer that would stop the egg tempera from properly oxidizing/curing, and could cause potential bloom or mold problems.  Your thoughts?



  • Question asked 2018-10-11 13:53:09 ... Most recent comment 2018-10-12 21:35:50
    Rigid Supports

    Good afternoon,

    I am a pastel artist who is searching for a lightweight aluminum substrate to mount pastel paper that can be used in the studio or in the plein air environment. The papers that I am considering to bind to the substrate is Sennelier LaCarte (This surface is created with finely ground (pH neutral) natural cork applied to a 170 lb. (pH neutral) board similar to cardstock) as well as UART paper product (sandpaper material mounted on 4ply or 8ply Conservation Board).

    There seems to be many aluminum products available yet looking at your document "Rigid Supports" I have a few questions regarding your selections. The doc states to use a product that has a plastic core yet most are available from 2-5 mm in thickness. A product by the trade name Alumalite has a fluted plastic core and available in 3/8" and 1/4" thickness. Since I paint out of doors the thicker gauge material seems optimal to avoid bending corners and edges of the surface in the outdoor environment. Is the fluted core acceptable? What is the minimum thickness appropriate to avoid warping? A local distributor stated that Dibond and Alumalite are pre-painted with a white aluminum finish yet your document states to avoid anything that does not have a polyester coil coating. The coating that you are referring to is it a high quality pre-painted finish onto the metal prior to fabrication-heat cured/cooled and rewound for shipment? If both substrates are acceptable do you recommend cleaning the panel with 99% isopropyl alcohol prior to applying an adhesive or what cleaning product is preferred? Also what adhesive(s) are considered appropriate to bond the aforementioned pastel surfaces to the aluminum substrate (BEVA 371 adhesive film/other)?

    Thank you,


  • Question asked 2018-07-25 19:53:57 ... Most recent comment 2018-10-11 21:34:43
    Paint Making Paint Mediums Encaustic

    ​I experimented with 100% carnauba wax and pigment on a hide glue gesso ground. As you probably know it was hard and glossy, but brittle, and it was easy to chip off. I am reluctant to add dammar because it may yellow. I considered Canada balsam, but after looking into it seemed that it might have the same problems as dammar. Could a hydrogenated rosin help, or microcrystalline wax? II found an article from the food industry that found polysorbate 60 was an effective plasticiser for carnauba, but I think that would make it susceptible to moisture. I  understand my responsibility to do my own tests, but any suggestions on what I might test? 

  • Question asked 2018-10-05 17:44:20 ... Most recent comment 2018-10-10 19:08:05
    Drawing Materials Health and Safety

    ​I just received a lead point and lead-tin point from Zecchi's.  How readily is lead transfered to the skin via either the stylus itself or from marks made on paper (i.e. resting a hand on a drawing)?  Any  other lead point consdierations I should keep in mind?


    Koo Schadler

  • Question asked 2018-10-05 14:31:30 ... Most recent comment 2018-10-08 15:17:07
    Oil Paint Art Conservation Topics

    ​Jerry's artarama makes an aluminum metal surface on which they claim you can paint directly onto. My question is can really I use oil paint directly on this surface (without any gesso) and will it last or will it chip off over time?

  • Question asked 2018-10-05 00:08:06 ... Most recent comment 2018-10-07 01:58:47

    I have an Ampersand Gessobord which has an additional 2 coats of acrylic gesso and a thin layer of oil colour using Liquin. I would like to adhere a small oil painted sheet on Daler-Rowney Oil Painting. Is this possible? What should I use as an adhesive?​

  • Question asked 2018-10-05 08:52:09 ... Most recent comment 2018-10-05 21:20:18
    Varnishes Oil Paint Art Conservation Topics

    ​Is there any particular reason why Regalrez 1094 is prefered as a varnish over Regalrez 1126? I gave up on using 1094 as a varnish a number of years back--I just don't like how it handles, or how it's really finnicky and tends to form an uneven sheen (and its high solubility means that you can't really apply multiple coats to even out the sheen), and I don't like how it tends to get tacky when you touch it, or when it gets too warm in my studio. Its glass transition temperature is so low that it can be above Tg at room temperature, on a warm day! That may not be a problem in the carefully-controlled climate of a museum, but for a painting that's going to be hanging in someone's house, and that may need to be shipped in the mail (how hot is it going to be in the back of that UPS truck?), it's a problem. 

    So I went back to using dammar, because while its aging properties are inferior to those of Regalrez, it makes an aesthetically pleasing varnish that is easy to use with predictable results, and its Tg is high enough that it's not going to get tacky and turn into a dust magnet just because you don't have the AC turned on. 

    But doing some reading on varnishes, apparently Regalrez 1126 is a possible alternative? It has a higher molecular weight and a higher glass transition temperature than Regalrez 1094, but is otherwise chemically identical. Is there a reason why 1094 is (seemingly) preferred variant for varnishes?


  • Question asked 2018-10-05 10:18:03 ... Most recent comment 2018-10-05 17:45:16

     Over the years I've had several people give me boxes of old pigments they no longer want. 

    1.  One box dates from1970s, NYC.  It includes labeled jars of lead white and Naples yellow (the latter genuine, I presume).  There are also many unlabeled jars of beautiful, turquoise colored pigments in various shades, akin to rich versions of dioptasio or malachite – but I'm doubtful malachite or dioptasio were commonly sold in NYC art stores in the 70s.  I'm thinking they are more likely some other copper color (and should be handled with caution).  Any thoughts?


    2. Another box contains pigments bought at a tiny Italian color shop in Perugia – wrapped in wax paper with scratchy handwriting to identify them, not always legible.  A bright yellow pigment is "Cromo", so I presume it's genuine chrome yellow and should be handled with caution?  Another color is bright green, the writing something like "vinyulto" (very hard to read) – any guesses?  An orangey red that looks like vermillion is labeled "scarlatto"– any idea what exact pigment the term scarlet refers to?


    3.  Finally, one box contains about a gallon of a fluffy black pigment, some sort of carbon I presume, maybe lamp?  One of my least favorite colors.  I could drop it off at a hazardous waste disposal day but we rarely have those where I live.  Is it okay to just throw away or scatter carbon black in the woods?


    Thanks.  And I'm not taking anymore boxes of old pigments!

    Koo Schadler



  • Question asked 2018-09-12 15:06:18 ... Most recent comment 2018-10-03 19:56:08
    Oil Paint Rigid Supports


    Various types of aluminum sheets are available. Which material is best suited as a foundation for oil painting?

    • Al99,5
    • AlCuMg1
    • AlCuMg2
    • AlMg1 (can be anodized)
    • AlMg2Mn0,8
    • AlMg3 (can be anodized)
    • AlMg4,5Mn0,7
    • AlMg5
    • AlMgSi1
    • AlZn4,5Mg1
    • AlZnMgCu0,5
    • AlZnMgCu1,5

    I'm thinking about painting directly on a sandblasted surface (the first layer with titanium white (linseed)).

  • Question asked 2018-09-30 12:36:58 ... Most recent comment 2018-10-03 19:17:28
    Watercolor Flexible Supports Matting, Framing, and Glazing

    ​Would it make sense to apply this plastic/aluminium backing (homemade version of Marvelseal) to thick watercolour paper before framing it, to prevent potential future contamination?

    Is this also helpful with canvases?

    The article only seems to talk about boards:

  • Question asked 2018-10-03 09:19:22 ... Most recent comment 2018-10-03 18:48:52

    ​I am a printmaker who uses oil-based ink on cotton rag paper and sometimes on mulberry for both relief work and monotypes. I've sometimes used oil paints, after allowing some of the oil to be absorbed by paper towels. I'm wondering why I don't have to seal my printing papers (Rives BFK etc.) but on canvas, you would need to use gesso.

  • Question asked 2018-09-30 19:16:31 ... Most recent comment 2018-10-01 07:49:02
    Rigid Supports Flexible Supports Oil Paint Grounds / Priming Sizes and Adhesives


    I'm trying to find the best way to prepare my supports so that I can have the longest lasting paintings possible. This is my current process, I use commercially made birch plywood panels that are cradled with basswood. These are the ones I use

    This is my current process

    1.    Sand the panel to make it smoother using fine or extra fine grit paper (usually 220). Wipe off dust or vacuum the panel to get rid of any debris. (I use a dry cloth because I don't know if it's okay to get it damp)

    2.    Apply 1 coat GAC 100 to the front and sides, and let it dry enough that I can turn it over without it sticking to anything (usually 20-30 minutes roughly)

    3.    Coat the back and inside edges of the panel, then let it dry with the back facing up for 2-3+ hours (I use a smooth but semi-firm nylon brush to apply the GAC 100, it helps minimize brush strokes)

    4.    Repeat the process above to coat the front and the back again, but this time let it dry for 3+ days

    5.    After 3+ days I apply acrylic gesso with a very soft camel hair brush or a soft nylon brush. If the gesso is thick I use a stiffer brush or water it down. I apply 2 coats but if I water it down I add more to compensate, usually only 3, sometimes 4. I wait the around 4+ hours between new coats depending on how cool to the touch it feels.

    6.    I let the gesso dry for 72+ hours before painting because I've seen that recommended by a few companies/artists including Golden. Then I start painting

    I do want to add a few steps to help my paintings be more archival. First I want to start mounting cotton canvas to the panels using BEVA film, before the gesso step. I would then use GAC 100 x 2 coats to help block oil penetration to the canvas. After that I would continue with the gesso step, but this time add a third layer. The third layer would be clear so I can draw my design on the second layer with pencil first and then seal it, to avoid having any graphite transfer through to the paint. Finally I would finish by using a 50/50 mixture of Galkyd Lite and Gamsol to thin out a colour I want to use for the ground layer, and then paint it over the gesso and wipe away the excess to leave an even tint. I was told this is a good way to increase adhesion for future oil paint layers, especially if you do heavy impasto which I want to explore more.

    I'm using those specific wood panels because they are the only ones I can access easily where I live in Canada, and I'm using 10oz cotton duck canvas because I can't afford linen (yet). I'm an art/design student, I don't have a big budget. 

    One thing I saw mentioned in another thread here was that GAC 100 is really bad as a moisture barrier, so I was wondering how much this matters with the panels I use since they are 3 ply and cradled? Do I need to do the priming method listed here instead? - if so, how would that change my current method? Also how much ventilation would I need because I don't have anywhere to work with a ventilation system. I do all my work in my room and avoid anything with fumes, or do it right by the open windows.

    I havent painted much all year cause I've been fixated on solving the issue of "what support is best?" and I know that's a subjective topic so I'm hoping someone with proper expertise here can help me out. Thank you for taking the time to read this

  • Question asked 2018-09-26 16:05:07 ... Most recent comment 2018-09-27 03:34:00
    Drying Oils Oil Paint Paint Additives Scientific Analysis Technical Art History Pigments

    FYI in case it proves useful for reference

    I have just completed my first proper test of clove oil for extending oil paint drying time. Although I have used it for a few years I've never tested it out properly with different pigments.

    For this test I mixed several of my core paints I use (cheap, low chroma, high opacity) with walnut oil until they took on a slippery quality. I then applied each mix to two separate sheets of PET-G with a W&N clear acrylic gesso ground.

    Each sheet was stored in an A4 sided clear plastic folder and sealed (so probably not air tight, but not open to freely moving air). They were stored side by side in a dark (but not totally light free) house temperature environment. Each night I would open both boxes and test if the paint had dried by drawing down a vertical line with the use of a rubber shaper tool.

    One sheet was left as it is, while the other had a cotton wool pad placed inside and two drops of clove oil were added to it each night. So no clove oil was added to the paint itself and the paints on each sheet came from the same mix. I then recorded once a day over a period of 14 days for each sample when they had touch dried.

    The results were surprising.. and interesting. I didn't expect to see much variation in drying times in the same pigment between brands. If anything I expected that the stiffer brands which had more walnut oil added might take longer to dry.

    Instead I found the complete opposite! The stiffer paints seemed to not have their drying time extended very much at all by the clove. I am not sure if this is due to the the presence of driers, or waxs/aluminium stearate in the paint to add body. Or maybe it's for another reason as yet unknown?

    I though I would share the results as they might prove useful to others. Next I want to examine the difference with clove oil present in the actual paint, as well as not replenishing the clove oil drops each day.

    Photo of the folders used and test surfaces:


    Final results, stopped after 14 days.


  • Question asked 2018-09-24 11:15:46 ... Most recent comment 2018-09-26 16:01:43
    Oil Paint Paint Additives Scientific Analysis Technical Art History

    I have read many times where people have made statements about the durability of paint films. Statements such as linseed oil produces the most durable oil paint film, or that slower drying paints tend to form softer weaker films, or that additives like clove oil, resins or other additives can make a less durable paint film.

    My question, is what does that actually mean in practice? Are differences in durability in a paint film measurable by a microscope, or other chemical or other scanning tests? Are differences only apparent in bending tests, or do they relate to delamination in real world paintings.

    Does a 'less durable' paint film mean it is more likely to delaminate, or that it will withstand less stress and strain? Will a painting done in linseed oil on dibond last longer before cracking than the same painting if done in say safflower oil? Or is there no appreciable difference?

    I realise these are impossible questions, but I hope you can feel my frustrations about the lack of answers regarding what a 'less durable' paint film actually means..

  • Question asked 2018-09-24 14:11:27 ... Most recent comment 2018-09-25 12:22:03

    ​Is there anything I can do to get the odour out.  It is acrylic on a gallery canvas? It has some yellow spots on the back of the canvas

    I have tried putting it in the sun outside and a vinegar wash but does not get rid of it.  Thank you for any help you can give

  • Question asked 2018-09-19 16:13:43 ... Most recent comment 2018-09-22 06:45:05

    Hi MITRA Team,


    I am inquiring on information that would support the use of  White Oil Base Primer paints (sold through paint stores/major home improvement stores ) as an alternative to Gesso and/or for adding as a top layer to the existing Gesso foundation.  


    I recently re- read some articles and books written by artists and several mentioned that they used a White Cover Stain Oil Based Primer sold through hardware /paint stores for sealing canvases. Some applied the Oil Primer as the top layer over Gesso  and others stayed with an oil base for all layers. One or two articles actually mentioned the name of Zin_ _ _ r Oil based primer for indoor/outdoor applications.


    Has anyone tested and/or heard about using traditional oil based primers that are normally available for household/commercial paint stores on artist canvas and/or panels?


    Is there any reason NOT to use oil based primers that are available through paint/hardware stores?  


    Looking forward to your reply.


    Patrick McGuire

  • Question asked 2017-03-15 06:53:44 ... Most recent comment 2018-09-22 06:07:50
    Flexible Supports Grounds / Priming

    ​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 2018-09-10 17:31:10 ... Most recent comment 2018-09-10 22:43:07
    Oil Paint Environment Studio Tools and Tips

    ​I am wondering what harmful residues or contaminants  might be introduced into the paint film during cleaning of palette, wiping off brushes during painting, etc. that may be present in general paper towels/ blue automotive shop towels and if it is worth the investment to use a higher quality rag. There is a product called sontera ec wipes, which market the product as containing no binders, etc. is there a conservator recommended product for general painting rag use? Wouldn’t even old t shirts etc have laundry detergent residues on them? 

  • Question asked 2018-09-06 13:09:37 ... Most recent comment 2018-09-10 12:30:12
    Drawing Materials


    I have some metalpoint questions.

    1.  I have a metalpoint friend who no longer uses his favorite grounds - Golden's Pastel Ground and Sandable Hard Gesso - because he is concerned with the warning labels (i.e. can cause cancer).  I presume the warning is due to silica content in both grounds - is that correct?  Any other reason? 

    2.  I presume it's sufficient to wear a good dust mask to address the issue?  Even with a mask my friend doesn't like creating dust because he figures it ends up somewhere.  Is there any harm to these sanding dusts if wiped up with a damp rag and put in the garbage?

    3.  My friend also had problems with "fading" in metalpoint drawings. He understands they don't literally fade but rather the metal isn't adhering well long-term; he feels he probably over-sands his ground, doesn't leave enough tooth for the metal to be deposited within. 

    My question is, how does a metalpoint line actually "adhere" to the ground?  Is it merely that metal deposits get "lodged" within the interstices of an irregular surface; or is there another sort of adhesion (such as electrostatic adhesion)?

    4. I want enough tooth in a ground to maximize the potential for dark lines, and to create a good bond between metal and ground.  On the other hand I want a smooth surface so my nib doesn't skip or leave dark flecks when drawn across areas with more texture. Any thoughts on how best to achieve these contradictory aims?

    5. Another conundrum of metalpoint drawing: the more one works a surface with a metal nib, the more smoothed the surface becomes, ergo the less abrasive it is and the less metal is deposited. 

    One way I address the problem (i.e. the surface is smoothed by the act of drawing itself) is this: Once my drawing is more or less developed, I'll occasionally apply a very thin, transparent layer of whatever ground I'm using over the entire image.  This whisper thin "scumble" of ground slightly obscures the drawing, yet it's still visible; the fresh ground reinstates "tooth" so I can go back in and deepen my darks and build up the drawing again, but richer and more multi layered. 

    Do you see any problem in putting a very thin layer of ground on top of a metalpoint drawing, and then continuing to work on it (and potentially repeating that process several times in a drawings?) FYI, I use different grounds - gouache, casein, acrylic polymer gesso, traditional gesso - although the same ground throughout a single drawing.

    I have more metalpoint questions – but that's enough for now!  

    Koo Schadler 



  • Question asked 2018-09-06 22:05:09 ... Most recent comment 2018-09-07 21:56:42

    An exhibition of some 25 bronzes by Rodin is opening tomorrow, Sept. 7, 2018 at the Jundt Art Museum at Gonzaga University in Spokane, WA. I will be writing up a review for a regional arts magazine called Art Chowder. Two of the pieces are owned by the Jundt and they have a typical, and very pleasing, aged bronze patina. The majority in the show come from the Iris and B. Gerald Cantor Collection​ and they all have a black patina. Some conservators came to "polish" (I was told) the 22 pieces from the Cantor Collection. The museum's preparator had asked the conservators about this matter and they really didn't have an answer about the nature of or reason for this black patina. It really is black and very shiny, and to my eye competes with the sculptures' form. Is anyone on MITRA familiar with this? I'd like to address it in the article (will cite source) because i'm sure visitors will wonder.

    Thanks very much!

  • Question asked 2018-09-05 08:55:44 ... Most recent comment 2018-09-05 16:34:23
    Handling and Transportation Paint Making Storage Studio Tools and Tips

    ​Dear MITRA moderator,

    I start make my oil paint out of pigments and linseed oil, nothing else, and I don't know how to store large amounts like 200 to 500 ml.

    One year until now I used plastic syringes for small amounts and had no problems.

    My first question is: What do you think of keeping this paints in plastic syringes? Would paint react with plastic envelope?

    My next question is more general:

    What do you suggest as best way to store linseed oil and pigment paint?

    Empty aluminium tubes are not economical for me and glass jars load with oxygen during use. Do you know if empty aluminium tubes can be used more than once, I mean can I open them again after use and fill?

    Kind regards,


  • Question asked 2018-08-27 22:34:54 ... Most recent comment 2018-08-31 22:34:26
    Varnishes Oil Paint

    ​This is a great resource! thank you for the support.

    A long winded question:

    I have looked at the reasons for the issues of sinking in.

    I have looked over the technical docs. around vasrnishes and I have corrected my process to (hopefully) avoid the following problems in the future.

    However I have a few older paintings that I need to "correct'" as the Gamvar varnish I have applied has been beading, uneven, spotty and dripping.

    I want to try and carefully remove it or somehow even it out.

    Here is the lowdown

    I use a generous amount of chromatic black. My mixture is a combo of Aliz Crimson, Prussian Blue and Raw Umber.

    Because of the dose of Raw umber, and the fact that I was using too much thinner, I consistantly had areas that "sunk in."

    As a result I was correcting this issue by oiling out using WN Artists' Painting Medium as I painted to bring back the details and rejuvinate the work. Occassionally, I would apply this over the entire work when I was finished to create the most even appearance. Sometimes this worked well.

    However, after letting the paintings dry for 6 months I tried to apply, (2 coats thus far), of Gamvar as a varnish and it failed to sink into the work and beaded and ofter dripped as mentioned.

    My question: Is the non adherence and innefectiveness of the varnish a result of oiling out with the WN medium? Can I remove this with OMS or mineral spirits? and what is your opinion about the WN medium? 

    Also looking for expert help in and around the Hudson Valley if I do have to remove the varnish...

  • Question asked 2018-08-23 15:31:48 ... Most recent comment 2018-08-31 12:46:41
    Oil Paint Sizes and Adhesives

    ​I have a piece of dibond that was sanded and had 2 layers of Bullseye 1-2-3 primer on it and then an old acrylic underpainting for a painting I never started.

    I primed the dibond again with 3 coats of Bullseye 1-2-3 primer over the old acrylic painting and lightly sanded the last layer with very fine grit sandpaper. I then painted a undiluted acryic underpainting with fluid consistency.

    After a few days I painted with oil paint thinned with pure walnut oil and found that around 4-6 hours later parts of the paint were dry and non-shiny as though the oil has been sucked down into the primer/acrylic underpainting.

    In this case I am guessing that the (in total) 5 layers of bulleye 1-2-3 primer resulted in a too absorbant surface, but I expected the acrylic paint to seal the primer to some extent. But it seemed to have no effect judging by the speed the oil paint was sucked into the primer.

    Is this perhaps due to the acrylic resin used in the paint or a property common to all acrylic paints due to their open surface nature? (in contrast to the closed nature of oil paints).. Are all acrylic paints absorbant to oil?


  • Question asked 2018-08-29 23:00:19 ... Most recent comment 2018-08-30 10:41:23
    Oil Paint Paint Mediums Solvents and Thinners

    ​Hello MITRA folks.

    I just came across this product, and wondered if anyone here has had any experience (especially using it as a toning or underpainting medium) with this product, Natral Earth Paint "Eco Solve?"

    Thanks for any thoughts!

  • Question asked 2018-08-29 01:34:03 ... Most recent comment 2018-08-29 12:26:43
    Oil Paint Art Conservation Topics Drying Oils

    ​I have a blot of oil paint about the size of a nickel that penetrated my Liquitex Matte Medium prime/size layers into the back side of the canvas (36x36 inches). It came from an early layer that was lean and thin, dilluted with odorless mineral spirits. This painting has been entirely dried and hardened for about 5 months. Given that the oxidation process of oil paint is no friend to cotton duck canvas (18-24 oz mine) what would you do to help the long term integrity of the painting?

    I had considered applying acrylic gesso to the oil blot, or even the entire backside of the canvas, applying layers thinned slightly with water to soak deep and contain any oil leakage. I have researched (to no avail) the conservation of Francis Bacon oil paintings on raw, unprimed and unsized canvas which I sought as a precedent. 

    Thank you for your help!

  • Question asked 2018-08-21 13:53:58 ... Most recent comment 2018-08-27 17:42:31
    Oil Paint Acrylic

    Hello and thank you in advance for your time.

    A few days ago, I painted a portrait on a 6"x6" gessoed wood panel using oil paints, or at least that's what I thought. When my paint tubes break, as they sometimes do, I put the leftover paint into small, clear jars. Unfortunately, a jar of acrylic ochre somehow snuck into my drawer of oil paints. I didn't notice anything fishy until the next day, when I returned to my palette and discovered that all of my paints were understandably wet with the exception of the hardened acrylic color.

    This painting has a light acrylic underpainting which I applied many months ago. The rest was completed a few days ago in one sitting. The use of this color is not isolated- it is incorporated into the whole portrait. However, although it was mixed into most of the piece, it is not neccessarily the majority color. I relied more heavily on reds, whites, and yellows when creating the skin tones. Removing the paint would mean destroying the work completely, which I am not prepared to do.

    I am wondering two things: 

    1) What will happen to my painting if I leave it as is?

    2) What options are available to me to attempt to rectify the situation? Would varnish or resin help hold it together?

    Thank you for your time.

  • Question asked 2018-08-22 01:20:45 ... Most recent comment 2018-08-23 11:56:38
    Grounds / Priming Oil Paint

    ​I'm not sure if it's kosher to ask for thoughts on specific products here, but thought I'd risk it, as I can find no reviews anywhere for the new "Michael Harding Non-Absorbent Acrylic Primer" that came out in late 2017. It is advertised to "not suck out the oil from oil paint, thus preventing sinking in." But doesn't an acrylic gesso actually need to have some absorbancy to bond with oil paint? I'd LOVE to find an acrylic gesso that I could scrub a solvent-free Imprimatura into without it's absorbency preventing a really light layer of paint, but this seems too good to be true... Thoughts would be much appreciated.

  • Question asked 2018-08-16 06:00:30 ... Most recent comment 2018-08-18 11:31:46
    Oil Paint Paint Additives Paint Making Industrial and Non-Traditional Products Pigments Scientific Analysis Technical Art History


    I recently came across a very insightfull book by Max Doerner.

    In the book he mentions that the strength and archival longevity of ancient paintings can also be attributed to the fact that the pigments were ground much more course,providuing a greater adhesion of the pigments to the oils resulting in a very durable paint film in contrast to what we have in modern times,that modern colormen risk creating very weak oil paints by grinding the pigments too finely in their persuit of color brilliance andsmooth paint consistency.Though it can be rectified somewhat by adding finely ground pumice stone or marble dust to give the paint film some grit.

    On the surface this makes sense to me in many ways but would like to hear your opinion on this matter.

    Thank you.

  • Question asked 2018-08-17 10:58:06 ... Most recent comment 2018-08-17 12:30:59


    I have a friend who owns a Maxfield Parrish painting (of a farmer accompanying his oxen at sundown on a wintery day.  She believes it was on the cover of Collier’s Magazine Jan. 1906; her in-laws bought it at Vose Gallery, Boston in the 1960s).  It isn't in great shape - has smoke damage (they hung it over a fireplace) and a few small areas missing paint. She is looking to get it conserved.  

    I recommended she check out the American Institute of Conservation (AIC) website to find a conservator. I've had good luck with AIC in the past.  However I'm wondering, since it's a work by a well known painter, if a greater level of scrutiny is warranted.  

    When a painting by a "famous" artist needs attention, is there any interest in or means by which it could/should be brought to the attention of historians or conservators; or are there just too many paintings by well known painters in private collections to warrant such attention?  Just curious.


    Koo Schadler


  • Question asked 2018-08-09 12:34:51 ... Most recent comment 2018-08-16 11:39:39

    ​Hi, Is 1-shot lettering enamel alkyd based? Would artist's alkyd paint be compatible with this enamel?

    While I'm here, does anyone have experience with the medium Smith's Cream? It has been recommended to me to use with  lettering enamel. 

    I'm trying to decide what type of paint to use on a traditional landscape painting to be installed outdoors. ( I just can't manipulate acrylic and I'm afraid that the artist's alkyd paint is very much like acrylic to handle. ) So, I got a few considerations. The other artists may be protecting their work with uv protection  and graffiti protection. Apparently, the 1-shot won't need this extra coating.

    Thank you!

  • Question asked 2018-08-05 11:25:11 ... Most recent comment 2018-08-15 11:00:30
    Acrylic Varnishes Art Conservation Topics

    ​I work for an artist who paints acrylic on canvas. He would like to collage an inkjet print to the acylic-primed canvas (using Lascaux 303 to adhere). There may be a minor amount of additional paint application around the edges of the print after it has been applied to the canvas, but otherwise, the surface of the print will remain untouched. I usually finish off his paintings with a coat of Golden Soft Gel Medium and then two coats of Golden Polymer Gloss Varnish. So, my question is... (from a conservation point of view) would it be alright to cover the inkjet print with the soft gel and varnish as well, or is there another product I should be using to protect the print separately?

  • Question asked 2018-08-09 12:10:08 ... Most recent comment 2018-08-15 09:51:36
    Environment Varnishes Oil Paint

    ​Is it reasonable to think that a painting done with artist's oils ( on an mdo properly primed board) will withstand the weather and sun exposure with several, 5, coats of uv protection, archival spray varnish? Is there another better product? The project I am working on will be installed outdoors 6 months of the year, hopefully to last several years. Thanks so much! 

  • Question asked 2018-08-09 12:46:10 ... Most recent comment 2018-08-11 17:56:02
    Drawing Materials

    ​Is it recommended to frame silverpoint/metalpoint drawings under glass? Will it affect the oxidation process? How long will the oxidation process go on for?


  • Question asked 2018-05-10 15:00:04 ... Most recent comment 2018-08-08 00:00:01
    Health and Safety

    ​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 2018-08-01 14:14:07 ... Most recent comment 2018-08-05 16:37:43
    Oil Paint

    ​Hello MITRA folks. I can't find the reference within the forums here, but I seem to recall that someone expressed some hesitation about using water-miscible oil paints for an underpainting for further regular oil layers (for a solvent-free approach to oils). Something about "they haven't been around that long to demonstrate their long-term archivalness." That was also said about acrylics used for the same purpose, and apparently they are now proven to be reliable. Would someone comment more on the use of water-miscible oil paints for an imprimatura and/or underpainting for regular oils? Thank you so much!

  • Question asked 2018-07-31 10:49:22 ... Most recent comment 2018-08-04 19:41:08

    ​this is a reply offering clarification as to the type of coating I wish to apply to wood turnings. From my readings it is said that oil varnishes are better then Spirit varnishes. I wish to prepare And apply a permanent coating that seals, vrmains flexible and is a high gloss.  

  • Question asked 2018-07-30 23:24:07 ... Most recent comment 2018-07-30 23:04:00


    The response you gave me is a starting point for me. 

    For years I had mixed Carnauba wax (highest grade, light amber) with beeswax (bleached) in proportions of 3 parts carnauba was to 1 part beeswax. The wax is supper hard. Should one drop a stick it shatters like broken glass. After polishing the hardwoods turned up to grit 600 the wood apeares like mable. All sanding is performed on the lathe in motion. I would press the hard wax stick against the wood and then buff it with a soft  cotton cloth. This application yielded a high gloss surface. But the finish doesn’t hold up over a short time of handling. The wax would dull. I am seeking to produce a mirror finish (high gloss) on the exterior of the turning that is more durable to handling with bare skin.hands.

    The link you gave me about violin finishes is a good start. I will experiment with some of the formulas presented. I did not have any recipes. Given the time and expense I did want to proceed without any glue as what should be the ingediants and amounts. 

    Any finish has to be flexible that is why I mentioned kiln dried wood verses air dried woods. 

    You mentioned that the furniture restoration conservators may have their own formulas. If you can offer a link to them that would also be something I would investigate. 

    Any finish I apply should seal the wood from moisture changes and offer a hard durable gloss that hold up. 

    Thank you for responding to my initial inquiry. Everyone’s time is limited and I don’t want to waste any bodies time. Thank you.

  • Question asked 2018-07-28 02:17:17 ... Most recent comment 2018-07-30 16:01:38
    Storage Oil Paint Art Conservation Topics


    I recently moved studios and used pieces of corrugated cardboard (made for mirror boxes) in between the faces of the paintings- the surfaces of the paintings (oil on canvas, dry paint) to protect the textures from rubbing and scratching each other. After the move, I left these sheets in between the paintings for storage for similar reasons, but then remembered the acidic negatives of cardboard and wanted to know if this practice should be avoided. Is storing paintings in contact with cardboard going to be problematic related to the acidity?

    Similarly, is there a best practice for storing a large amount of paintings fairly tightly packed in the studio while protecting the surfaces? 

    I am aware that not having light on the painting will be a long term issue, but perhaps plastic wrapping is preferable. In the past I have just gone dry face to dry face, but my surfaces have gotten more delicate and need more protection...

    Thanks so much for any insight! I´ll research resource archive here in case this is discussed elsewhere.


  • Question asked 2018-07-26 00:24:06 ... Most recent comment 2018-07-27 23:51:58
    Grounds / Priming Industrial and Non-Traditional Products

    ​Hello everyone,

    I have a question regarded priming of linen canvas. I have streched over 100 canvases and glued them with rabbit skin glue, and want to know that what would be the best primer over the glue which is reliable and trustworthy. I know that old masters used oil primer, but I have got so much different information that I am really confused. Someone told me that I can just buy regular acrylic paint which we use in homes for interior and make three coats of it on canvas, while others says that I should use oil primer. Some people go for the gesso version.

    What about the glue, next time, should I use GAC400/200/100 insted of rabbit skin glue?

    I have seen 19th centuries paintings on galleries, and the are almost vanished. The oil is cracking and the conditions are very bad. I saw a Picasso in gallery, and that was almost finito. This means that paintings which are made on acrylic background are not reliable.  


  • Question asked 2018-07-25 14:10:49 ... Most recent comment 2018-07-27 15:11:12
    Varnishes Drying Oils Other Solvents and Thinners Flexible Supports

    ​I work only with air dried woods that I have harvested for their unique figured grain characteristic. These woods will always move with changes in humidity., unlike kiln dried lumber whose moisture content has been reduced to 6%. I am no pleased with modern commercial synthetic varnishes that have a plastic look. I have read much on the subject of classical oil and alcohol varnishes utilizing tree resin. I don’t want to move forward without some advise from  persons with experience in making such varnishes. Given that each resin has different acid resin constituents and percentages developing a receipt by trial and error could be a life long expensive process. I have purchased a wide assortment of gums and resin based upon my readings but I am not applying this custom finish to canvas.  

  • Question asked 2018-07-20 22:22:27 ... Most recent comment 2018-07-26 21:52:17
    Acrylic Encaustic Matting, Framing, and Glazing Varnishes Watercolor

    ​Hello MITRA folks! Recently, I've come across several professional artists who are using encaustic over their watercolors on paper, sometimes layered with mixed media in the wax. I know encaustic has been around a long time, but I'm wondering if the encaustic (as an alternative to glass) a) is good UV protection b) will yellow or darken over time c) has long-term archival problems including dust, fragility, poliution, temperature sensitivity, physical damage, etc. and d) has an odor that lingers? On a related subject, I know that some artists use acrylic mediums and varnishes as an alternative to glass over watercolors, but I seem to recall that Mark Golden is somewhat cautious of this use of their products, stating that acrylic varnishes will change the appearance, texture and surface of a watercolor on paper, and that this approach is not as protective as archival framing under glass. But...varnishing a watercolor would essentially turn it into an acrylic painting, and a conventional acrylic painting which has been varnished with acrylic varnishes would also have this same vulnerability, wouldn't it? Or maybe not because the paint film would be thicker with acrylic paint? I'd really appreciate some light on all of these questions, if you are able. Oh, and it goes without saying that this would be on a rigid support. Thank you!

  • Question asked 2018-07-22 07:46:28 ... Most recent comment 2018-07-24 10:20:26
    Oil Paint Art Conservation Topics Paint Mediums Sizes and Adhesives

    ​I work in mixed media and sometimes add collage elements after I have already used oil paint.  Since conventional adhesives cannot be used on top of oil, I use the oil paint itself as the adhesive. Sometimes I mix in impasto. The materials I am collaging are lightweight, typically fabric or ribbon.  If I am using a natural fiber, I seal it first to prevent erosion from contact with the oil. Can anyone tell me if this is a good method, or recommend any alternatives?  I am concerned about collaged elements falling off over time.  Thank you. 

  • Question asked 2018-01-17 13:01:48 ... Most recent comment 2018-07-24 04:09:35
    Acrylic Oil Paint Other Watercolor

    ​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 2018-07-20 20:56:25 ... Most recent comment 2018-07-23 17:59:42

    ​Hello, I am working on a oil gilding project. I am gilding with 23k best surface goldleaf on top of a wooden, linen lined, gessoed board. I have used shellac for my first surface layer and for size application, I have used Lafranc Charbonoble 12 hr size. What is your best recommendation to seal the goldleaf after application is complete.

  • Question asked 2018-07-23 05:15:12 ... Most recent comment 2018-07-23 17:45:13
    Grounds / Priming Oil Paint Paint Mediums Other Studio Tools and Tips


    I am curious to know about the strenght and flexibilty of venice turp and stand oil considering is thick viscous body and how well it ages and if it might actually help the paint film be a bit stronger if either of these are used as mediums with additions of normal turp and oil and if they may actually increase the strength of oil grounds(I make my oil grounds by hand with chalk,pigment,oil and a bit of alkyd etc.)

    Thank you!

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


    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.



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

    ​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

    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

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

    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


    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

    ​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

    ​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

    ​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)?  


    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

    ​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:

    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

    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,

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

    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: 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

    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:

    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


    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.


  • 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

    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


    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?


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

    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!



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

    ​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!



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

    ​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

    ​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

    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

    ​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

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

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

    ​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

    ​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?


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

    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

    ​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

    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! :)


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

    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

    ​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

    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?

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

    ​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


    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?



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


    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

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



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

    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

    ​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.


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

    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

    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

    ​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

    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

    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.




    Cristian A. (artist).


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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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,  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

    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

    ​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?


    Koo Schadler

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


    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.

    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

    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

    ​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

    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."

    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

    ​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

    ​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

    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
    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

    ​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:

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

    ​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

    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

    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

    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

    ​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!

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

    ​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

    ​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!

  • 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

    ​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

    ​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

    ​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


    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.


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

    ​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,

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

    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
    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
    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

    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

    ​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

    ​Referring to your article about paint mediums and additives.

    [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

    ​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

    ​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,


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


    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?


    Koo Schadler

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

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

    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

    ​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

    ​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

    ​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

    ​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

    ​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.


    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

    ​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

    ​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

    ​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

    ​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

    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

    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

    ​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.


    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.


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

    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

    ​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

    ​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

    ​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


    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

    ​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

    ​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

    ​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

    ​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

    ​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


    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



    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:


    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?


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

    ​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

    ​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

    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

    ​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!


  • 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

    ​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
    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

    ​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

    ​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 ,


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

    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

    ​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  

    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

    ​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

    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

    ​ 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

    ​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?


  • 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

    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

    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

    ​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

    ​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?



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

    ​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

    ​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

    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

    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:

    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:

    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!

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

    ​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

    ​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

    ​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

    ​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

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

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

    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.



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

    ​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

    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

    ​🍁 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

    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

    ​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

    ​​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

    ​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

    ​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

    ​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

    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


    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

    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
    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.

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

    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

    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:

    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

    ​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

    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

    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?


    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

    ​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

    ​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


    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

    ​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

    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

    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

    ​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

    ​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

    ​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

    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


    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.)


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

    ​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

    ​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

    ​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

    ​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


    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:

    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

    ​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

    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?




    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

    ​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

    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!


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

    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. 


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

    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

    ​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

    ​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

    ​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

    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

    ​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

    ​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:

    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:

    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?


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


    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?


    Koo Schadler


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


    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


    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...?


  • Question asked 2017-07-19 16:31:15 ... Most recent comment 2017-07-20 19:15:29
    Watercolor Ink Gouache Flexible Supports
    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

    ​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

    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?


    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


    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:

    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

    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

    ​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


    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

    "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


    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

    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 ( Yet, looking at the SDS for Gamblin's Galkyd mediums (, 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

    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

    ​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.



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


    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

    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

    ​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

    ​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

    ​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

    ​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

    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


    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

    ​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

    ​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?



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

    ​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

    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

    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

    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

    ​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?


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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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

    ​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


       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

    ​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

    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

    ​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

    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? 


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

    ​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.


    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?


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

    ​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

    ​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! 


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

    ​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


    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.


  • 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
    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

    ​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

    ​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

    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).


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

    ​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
    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

    ​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

    ​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

     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


    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
    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
    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


    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

    ​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 2017-02-14 13:09:24 ... Most recent comment 2017-03-08 17:26:00
    Acrylic Industrial and Non-Traditional Products Scientific Analysis
    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
    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?

  • Question asked 2017-02-27 22:04:58 ... Most recent comment 2017-03-02 11:11:00
    Animal Glue Chalk Grounds / Priming Oil Paint

    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

    ​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
    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
    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
    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
    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
    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
    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
    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.? 


    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
    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
    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
    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
    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
    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
    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
    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.
  • Question asked 2017-02-02 09:43:44 ... Most recent comment 2017-02-02 17:29:00
    Oil Paint Varnishes
    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
    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
    Tuscan red
    Terra cotta
    Tuscan red
    Terra cotta
    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
    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.

  • Question asked 2017-01-31 11:51:09 ... Most recent comment 2017-01-31 16:07:00
    Drying Oils Alkyd
    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
    pva size for birch panel?
  • Question asked 2017-01-29 10:47:47 ... Most recent comment 2017-01-29 12:41:00
    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,


    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
    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
    birch support
  • Question asked 2017-01-26 10:01:22 ... Most recent comment 2017-01-26 10:11:00
    Oil Paint Pigments
    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.


  • Question asked 2017-01-24 12:43:49 ... Most recent comment 2017-01-24 13:55:00
    Chalk Drawing Materials Pencil
    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
    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
    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
    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
    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
    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
    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
    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
    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.

  • Question asked 2017-01-06 17:14:48 ... Most recent comment 2017-01-06 17:20:00
    Acrylic Flexible Supports
    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
    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
    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
    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
    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
    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
    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!


    Koo Schadler
  • Question asked 2016-12-27 13:10:38 ... Most recent comment 2016-12-27 17:53:00
    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
    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
    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?


    Koo Schadler
  • Question asked 2016-12-23 16:02:53 ... Most recent comment 2016-12-23 16:42:00
    Rigid Supports Oil Paint
    I just asked about painting oils on birch plywood, which I do directly, no primer. To see an example go to> 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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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, 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
    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.

  • Question asked 2016-11-30 16:15:33 ... Most recent comment 2016-11-30 16:47:00
    Pigments Technical Art History
    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
    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
    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
    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
    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
    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
    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
    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
    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 asked 2016-11-22 06:01:00 ... Most recent comment 2016-11-22 07:14:00
    Rigid Supports Sizes and Adhesives
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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. 
    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.
    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
    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
    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
    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 2016-11-06 17:27:55 ... Most recent comment 2016-11-07 01:28:00
    Egg Tempera Health and Safety Pigments
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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...

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  • This is a Moderator Answer - Click Here to view the full thread.

    At that point, I think that you are distorting and not really shrinking. I mean, you could ramp the heat up so high as to theoretically make a film out of it (hyperbole, I know). But that is way beyond what we need to deal with on this subject..

  • This is a Moderator Answer - Click Here to view the full thread.

    OK finally, finally. One of the tricks were use in painting conservation is to use a hole punch to punch out small circles of high quality blotter paper and push the tack through this before using it to attach the canvas to the stretcher. This makes it far less likely that the tack will be driven too deep into the canvas and cause a potential puncture. I know that some conservators and a couple of painters will staple their canvases through linen twill tape for the same precaustion.

  • This is a Moderator Answer - Click Here to view the full thread.

    Additionally, there is an unspoken (and sometimes spoken) bias that tacks on the side of the stretcher are better than staples. I believe that much of this opinion comes from disasters resulting from staples driven too deeply (the bottom of the staple should by countersink the surface of the canvas) and a failure to set the staples at a 90 degree angle rather than parallel to each other. As a painting conservator, I have seen innumerable cases where tacks were driven too deep and the canvas has pulled loose from the stretcher.

    I generally go with staples if on the back of the stretcher and tacks of on the sides.

  • This is a Moderator Answer - Click Here to view the full thread.

    We have had a couple of threads that are relevant to this topic. This one in particular

    and this as well

    As far as heat, a program trained painting conservator would test everything before any procedure. You could/should make their life easier by recording all of your materials and attaching that to your artwork (see our resources section). Finally, the heat used to line or consolidate a painting should fall below that of scorching a polyester fabric. The conservator would need to test, of course, but the temperatures indicated on a typical iron for ironing polyester fabrics is vastly higher than the temperatures used by ethical conservators.

    Finally, I do not believe that polyester fabrics can be pre-shrunk. One of their virtues is that they are not effected by moisture in the same way as natural fibers and do not shrink like linen and cotton.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​ ​We have covered most of this question on an earlier thread. Here it is for your perusal

    Additionally, one of our moderators has written a good synopsis of the various pros and cons of the two methods. The link is here

     I will say that as a practicing painter who primed my own canvases, I vastly preferred staples intelligently applied on the back of the stretcher (see the link) and as a painting conservator, I generally use tacks on the sides of the stretcher. Neither are from a worry about dislodging paint. If a painting is that fragile, it requires additional conservation procedures. I should add that I stretch unprimed/unpainted canvases face down and anything with painted imagery face up. The latter is far more difficult but is necessary for ethical conservation.

  • This is a Moderator Answer - Click Here to view the full thread.

    What he said ;)

    It is not simply about adding more oil when it comes to the rheology of paints BUT the addition of some oil/bodied oil can counteract the shortness induced by stabilizers (essentially materials added to tubed paints to keep the oil and pigment from separating) The prevention of oil separation is also the cause of shortness.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​You can start by adding a mixture of 3:1 refined or cold-pressed inseed oil and bodied linseed oil to your commercial oil paint, but you may also want to experiment with larger proportions of bodied oil to unbodied oil.

    We have found extender pigments, such as wollastonite, which has an accicular partcile shape, useful also in giving paint a longer consistency. However, there are many extender pigments and color pigments that can be used, especially when the pigments have heterogenous particle sizes and shape (variety of size and shapes), such as is often found with paints made with natural earth pigments.

    Oil paints that do not contain additives, such as castor wax, aluminum and magnesium stearates, tend to be longer, especially if the particle size and shape of the pigments are heterogenous.

  • This is a Moderator Answer - Click Here to view the full thread.

    Liquin is not a filller but a medium. It would loosen up the paint but not make it long. I am guessing that What George is suggesting is not adding additional filler to a commercial paint, which would just stiffen it. Likely he means that paint made with certain additional materials made a longer paint. I have found that certain grinds of barium sulfate added to lead white make a very long and even ropy paint in linseed oil. Hand ground lead white in linseed oil will make a rather long paint unless the paint is made very lean.

    If you want to use commercial oil paints that contain stabilizers like wax, castor wax, or aluminum stearate, your best bet is probably to add a bit of bodied oil or to grind up an appropriate filler in linseed oil (containing a proportion of bodied oil) to a rather loose consistency and add this to your commercial paint to the point where the paint behaves as you wish.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Adding wax to oil paint has the opposite effect making paint 'short'. Additives such as wax and pigment stabilizers used in commercial artists paint make paint short. To make paint more flowing or 'long' add bodied oil (stand oil) to your paint. It does not need much to make paint longer. Adding excessive amounts of bodied oil, however, will increase the tackiness or drag of oil paint.

    Some pigment extenders or fillers will not only extend paint but make ppaint longer. We found that pigment extenders with accicular particle shapes also tend to give paint 'long' behavior.

  • This is a Moderator Answer - Click Here to view the full thread.

    Thanks Matthew, I was teaching all day and am only now able to comment. The term usually refers to a binder extracted from egg white. The white is beaten to a froth and allowed to sit for a while the liquid that exudes from this is collected and called glair. Glair was more commonly used as a binder for illumination on parchment. It was also as an additional binder in water gilding where it supplemented the glue already in the ground and bole. It is a weaker binder than egg yolk and is probably best avoided outside of the above. As a side issue, some painters used glair as a temporary varnish applied before the work could receive a more permanent varnish. Very often this layer was not removed and it can be seen as a grayish turbid and generally insoluble coating. In short, this is not advised.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​That basic formula does appear in historical texts, at least essentially those ingredients. There are several recipes listed here:

     and additional recipes here:

    My "painting techniques" instructor, a knowledgeable tempera painter, warned against experimenting with glair, due to concerns that the resulting paint might be brittle and detach. I don't have any hands-on experience with this material in gilding or binding.

    A bone folder is a common tool in bookbinding and fine stationery, useful where clay coatings and painted surfaces might pick up indelible marks from metal tools. (Literally for folding and creasing signatures of paper, envelope flaps and folded cards. ) In this case, it's probably used because it's less reactive with acids. Unless I'm missing something, I think a glass or plastic tool would be just as good.

  • This is a Moderator Answer - Click Here to view the full thread.

    I am so sorry. Unfortunately, there are just way too many variables to be able to answer this question without be able to do actual tests on the painting. (IE was it varnished or unvarnished?, how much was the original paint thinned?, what type of spray paint?, etc) Conservation treatments are always case specific. You should really take it to a program-trained painting conservator.

  • This is a Moderator Answer - Click Here to view the full thread.

    I would imagine that there is a limit as to how fine or coarse the powder is ground before it becomes problematic. Too fine may make it hard to have the particles fully dispersed and too coarse could create a ground that is too rough to cleanly apply strokes of paint. However, for the most part, the choice of the type and grind of calcium carbonate or hydrated calcium sulfate is up to personal preference.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Matthew, it looks like we cross posted. Thanks for adding some practical info here.

  • This is a Moderator Answer - Click Here to view the full thread.

    There are far too many variables here for me to be able to answer this question. First evaporation rates are given as ratios compared to diethyl ether. Oil of turpentine is listed as 170.

    This does not tell us much but there are many more important factors here.  For instance, what cut is the varnish (how much turp to how much resin)? How thickly was it applied? What is the temperature in the space? What is the RH? If this is going to be in a hood, what is the airflow? What is the affinity of dammar to hold turpentine? Finally, I do not use dammar so I can’t speak even empirically on this. Perhaps someone else will take a stab at giving you a time range despite the difficulty of being very precise given the above.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​With old-fashined tree exudate gum varnishes like damar and mastic, the time required to achieve a tack-free coating can be irregular, depending on factors like ambient humidity. Many artists simply will not varnish on a rainy day at all, to avoid risking long-term tackiness. In my studio, I recall that a thin coat of factory-made damar dried to an acceptable, tack-free hardness in 2-3 days when humidity was low; homemade varnish would take a day or two longer. Drying rates were not uniform, though- sometimes a picture would remain tacky longer than was convenient, and I learned not to be in a hurry where damar was concerned. Years ago, I adopted acrylic solution varnish and found that drying times were more regular and shorter, and that removal (when necessary) was much easier, with less risky solvents. 

  • This is a Moderator Answer - Click Here to view the full thread.

    I like to apply sizing and at least some gesso to the back of the panel, if it is not very small, to diminish warping so I would seal after. Not getting shellac on the paint on the front is a reason for doing it first. You could always sand off anything that got on the front of the panel before sizing and applying your ground.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Just to add a couple of thoughts, two points that Sarah mentioned caught my attention: the issue of stiffness, and whether transparency is important. I think it's likely that any cradle or chassis behind a polymer panel of this thickness will cause some planar irregularity on the face. This is probably within tolerances for signage, but probably not for artistic painting. Also, it occurred to me that, if transparency/translucency is not important, the better choice would be to laminate the polymer to a rigid substrate. But, if one were going to do that, why not just paint on the substrate? 

    If the use of this specific panel material is important, I think it might be worth trying a shallow box construction, two panels enclosed on all 4 sides with a sealed cavity of dead space inside. The sides could be metal, proud on the face to protect the panel edges. Kind of like a double pane window. This is just a brainstorm, however.

  • This is a Moderator Answer - Click Here to view the full thread.

    Sealing with shellac is fine under an oil ground but I would not suggest applying shellac to the surface of a panel that will receive a glue bound ground. It would only cut adhesion and make the failure of the ground more likely. It would be fine to seal the edges and back with shellac but I would probably do that after completing the painting (a case could be made to do it first as well).

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Silly me - I will be editing my initial response as for some inexplicable reason  I totally  misread the size. By a lot! Anyway, you will see edits in a moment. Thanks.

  • This is a Moderator Answer - Click Here to view the full thread.

    Hi –

    I am writing a revised answer as I completely misread the scale of the work and that changes my recommendations somewhat. I will leave my original response below this one, however, as I do feel it captures our thoughts if ever going large, say something like 4'x5'.

    In terms of the sizes you mention, you could get away without crossbracing (which is generally frowned upon for other reasons – but that's another topic) as both of these materials are unresponsive enough to environmental changes that the usual cause of warping – changes in humidity – is really a non-issue. However I think perimeter bracing would be a good idea to facilitate handling, framing, and hanging. And to provide a little more rigiridty.

    Between the two options, I continue to like the composite panel. It has better rigidity and is lighter weight. Plus at this point it is such a common panel that confidence in its performance has been steadily improving. While acrylic sheeting is definitely durable, and has an excellent track record for stability, it remains just a very unusual choice and would see no advantage using it unless its transparency was important.  That said, if using either of them we would suggest using an acrylic dispersion ground. For both some surface scuffing would be recommended for maximum adhesion.

    In terms of attaching a perimeter bracing, there is a listing of structural adhesives approved for Dibond – and which are likely good for other brands as well – that can be found on page 36 of this Fabrication Manual:

     Buy also consult with the manufacturer with of the composite panel you plan to use for their advice.

    Acrylic panel would be more difficult and complicated to work with in this way So another reason to likely prefer the composite panel.

    Hope that helps.

    Sarah Sands, Senior Technical Specialist, Golden Artist Colors and Williamsburg Oils


    My earlier response is below where I misunderstood the scale involved

    * * * * * * * * * * * * *

    Hi - We do not have direct experience working with either of these materials at this scale, so what follows is just some general thoughts. In terms of thermal expansion, rigidity and weight, the composite panel really does seem to be the better choice. If you look through this brochure, which shares a lot of technical information and does some direct comparisons with other materials, you will get a good sense of its advantages (at least on paper):

    And here is a sheet on Plexiglas with similar technical specs:

    Other reasons I like composite panels are the fact that they are used a lot for large scale pieces in the commercial graphics industry, including billboards, display graphics, and exterior signage, so there is a wealth of information on how it performs at that scale and how best to mount them. While acrylic sheeting is certainly durable, to get the same stiffness you would need to go 2-3x the thickness and it comes with a much higher thermal expansion compared to composites. Ultimately, acrylic sheets are just a much more unusual choice at those sizes, with perhaps the sole advantage being perhaps its transparency, if that was important.

    In terms of sources for advice, I would reach out to the manufacturer or major distributor/retailer for these panels as they would certainly have experience of how these perform at that scale. And if you were willing to purchase a panel at that scale, you might take a look at Simon Lui, who fabricates large scale panels for a lot of artists in NY:

    He has a mechanical engineering background to boot, so comes to supports with a wealth of knowledge about materials and how they perform. And even just looking at his designs for integrating the panel with wood framing running along the sides can give ideas.

    In terms of acrylic sheeting, it can be primed with acrylic dispersion grounds, as Brian mentioned, and unless you truly need the transparency we would recommend that.  For more information, also avail yourself of the resources from someone like Plexiglas

    For both acrylic sheeting and composite panel you are working with very engineered commercial materials and the companies that make these really know the most about them - physical tolerances, how best to mount, the ability to span a large area unsupported, etc. Hope that helps. I can also say that we have worked with a lot more artists doing large scale pieces on composite panels then on acrylic sheeting and that alone says something.


  • This is a Moderator Answer - Click Here to view the full thread.

    What you describe is one of the reasons why it was always problematic to work on a dark ground. A transparent toning layer is probably a better choice but unless the highlights were applied quite heavily, they could lower in tone over time.

    I do not know of any studies on titanium dioxide converting to a soap over time. Certainly, zinc oxide does and it appears to cause more deleterious effects.

  • This is a Moderator Answer - Click Here to view the full thread.

    I have forwarded this question to a few others who may have more experience with this product and its applicability for fine art.

  • This is a Moderator Answer - Click Here to view the full thread.

    So sorry, your question seems to have slipped by me.  It is difficult to give an exact mathematical rule for the size of panel that requires backing. It is determined by the rigidity of the panel material, the thickness of the panel, the size of the panel, and the amount of paint or other materials that will be applied to the panel.

    I am also hampered by a lack of experience using PMMA as a support for fine art so I cannot really give you a thoughtful answer. Perhaps others here can comment. My preliminary thoughts are below but I would really hope that others with more knowledge of the subject could add something more authoritative.

    I would think that with PMMA panels, the most important protection would be to have it in some sort of frame (something like wood) which would absorb the impact rather than transmit the force to the panel, which could crack or break.

    Finally, if used as a painting support, I would suggest really scuffing up the surface to provide some mechanical tooth for the paint adhesion. An acrylic dispersion ground would also be sensible, as it would have a natural affinity for the PMMA panel

  • This is a Moderator Answer - Click Here to view the full thread.

    Really fading is not the issue in this instance. Increased transparency of oil films over time is a result of a couple of factors but primarily it is the conversion of certain pigments, primarily lead white and zinc white, into metal carboxylates (more commonly known as metal soaps). This occurs because of the interaction of fatty acids and mobile metal ions in the paint film.  This same can happen with other pigments but these are the most effected. In essence, basic lead carbonate has a refractive index of 1.94 and 2.09, which makes it relatively opaque in linseed oil which starts out with a refractive index of 1.48 -1.49. Lead carboxylates have a lower refractive index and if enough of the lead white is converted the film become less opaque. It is believed that this mechanism is exacerbated when the film is exposed to moisture and heat.

    Another less important factor is that aged drying oil films have a slightly higher refractive index than do newer films. This may cause a very slight increased transparency but the above mechanism creates a far more pronounced impact.  

    Given the above, I am not sure that your layering would really have any effect one way or the other. If it were an issue of fading the pigments at the surface would be far more sensitive than those below. We know this from cross-sections taken from historic paintings where the uppermost gradient of a fugitive color has little color but that same pigment below still retains its original hue.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Thanks so much Sarah.

  • This is a Moderator Answer - Click Here to view the full thread.

    Hi -

    So glad you asked this question as it definitely IS confusing and having a chance to clear up the situation is always welcomed. Plus, we also happened to write an article, beyond the blog post that Matt Kinsley mentions, that goes into it this and other changes in some detail:

    Beauty and the Best: Wrestling with Changes in Williamsburg

    I would also want to make sure if you do have a tube listing it as PY83 HR, as that would be a mistake and we would certainly want to know about it. And sadly we are aware that the mislabeling of a transparent version of PY83 as HR is not uncommon and it is always worth double checking. To just touch base on the main point of the article, here is the most relevant passage:

    "All of which brings us to the last three colors: Alizarin Orange, Alizarin Yellow and Indian Yellow. Unfortunately, the pigment at the center of these, a type of Diarylide Yellow, comes in various forms that all share the same Color Index Name of PY 83. As you can imagine, this can lead to some confusion when assigning a rating. The opaque version, which carries the additional designation ‘HR-70’ in its chemical description, has excellent lightfastness and is on the ASTM list of rated pigments. However, our testing showed that the transparent version Williamsburg had chosen could only be rated as Fair, or the equivalent to ASTM III. And here lies the crux of our quandary. These three colors have had exceptionally long and beloved histories within the Williamsburg brand, going back to its earliest days. Many painters who have used Williamsburg throughout these decades are passionately connected to their uniqueness, so a sudden change would be felt as particularly disruptive. And as if to confirm that, when searching for an alternative pigment we could use, we simply could not find anything with the same brilliance, transparency, and glow. So a choice needed to be made: dramatically change the look of these colors, discontinue them, or keep them as part of our offerings but clearly label their lightfastness as Fair, a rating similar to Alizarin Crimson."

    And here is the table of data that we show, which might be somewhat reassuring.  ASTM Lightfastness I allows up to 4 Delta E of change, and ASTM LF II allows 8. However, ASTM states - and we think fairly - that you must label the tube with the lightfastness of the weakest pigment. Thus why we list them as fair. But because they are mixed with very lightfastness pigments in the blend, they are just a touch over LF II in the very harsh South Florida Test, and would qualify as LF II in the indoor accelerated Xenon testing. And they certainly do better that Alizari Crimson, which many artists have come to accept.

    ColorPigment(s)South FloridaXenon
    Alizarin CrimsonPR8313.7212.26
    Indian YellowPY839.9210.38
    Alizarin YellowPY42,PY838.636.92
    Alizarin OrangePR177,PY838.095.53

    How you balance that risk/reward of some lightfastness concern in trade for color is obviously an individual thing.  And the use of a UV filtering varnish will definitely improve the performance and we would encourage it.

    Lastly, if you still have concerns about the color, or would like to exchange if for something else, just reach out to us directly and we will be happy to make that happen.
  • This is a Moderator Answer - Click Here to view the full thread.

    ​Williamsburg explained this in a 2015 bulletin:

    "...a transparent version of  PY83, a diarylide yellow that in its opaque form is among the most lightfast yellows available. However, based on the test results, this transparent version would need to be rated as Fair, or the equivalent of ASTM III, the same category as Alizarin Crimson. "

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Of the two types of paper mentioned, if I had to pick one it would be kraft paper. The sulfite stock used to make construction paper becomes yellow and brittle in a relatively short time, and the dyed colors of this type of paper tend to fade rapidly on exposure to light.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​In my opinion, selecting a durable paper at the start is always a better choice than trying to "cure" a self-destructing, scholastic-grade paper. In addition to the difficulty in stabilizing the materials, there is also the challenge of preventing acids from affecting other artwork in storage. For artists who feel they must use paper that is known to be acidic or prone to deterioration, it's advisable to take high quality photographs in case the original becomes too delicate to maintain and display.

  • This is a Moderator Answer - Click Here to view the full thread.

    It sounds like you are constructing the wood box and then adhering paper to it?  We need to know a bit more before we can help here:

    ·         Is quick tack a requirement?

    ·         How thin is the paper, is bleed through an issue?

    ·         Is the paper just wrapping the wood or are portions of it free standing as in a 3D construction?

    Once we know these details we may be able to point you towards some potential materials.

  • This is a Moderator Answer - Click Here to view the full thread.

    Oil colors bound in safflower oil seem to be resilient enough since they were introduced in the 20th century. Other oils may make slightly stronger films but you should be all right using safflower bound paints on both canvas and panel if you are follwing sound technique. It is true that safflower oil is sometimes described as a semi-drying oil and a drying oil in other places. Proper selection of the type of oil by the color manufacturer should ensure a quality paint.

    Yes, the mixing of colors also creates a paint with mixed attributes. How this works out in practice is still not completely understood and a 50/50 mixture of two colors does not automatically mean that the qualities of the paint film are an exact middle point between the two colors. In short, though, you should be all right.

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    I think that B-72 is a fine coating for the purpose. Oil paint would also be fine as long that the sides and reverse of the panel are properly sized to cut the absorbency. It would be porous enough to absorb surface grime but that would be alleviated by framing etc. I would probably use an artist’s alkyd paint just for the reduced dry time. Honestly, this is a place where shellac would probably be just as good as the other options.

    I am not sure that there would be a massive difference coating before or after painting. However, one could make the case that you might not want to create a water impervious back of the painting while you are applying layer after layer of water-borne paint to the front. If you did apply it first you would want to make sure that you avoid having any of the material get on the surface of the work and be a possible cause for local delamination.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​Spray paints contain a complex assortment of additives not normally used in artists' oils, or exceeding the amounts used in oil painting. These include driers and anti-skinning agents that can have a powerful effect on the entire thickness of the painting, along with powerful solvents. For these reasons alone, I would say that hardware store spray paint could be problematic if durability of results is important in your work.

  • This is a Moderator Answer - Click Here to view the full thread.

    ​I'm afraid I can't even hazard a guess about boiling or otherwise refining clay. I like your idea about using pigments from terrestrial (mined) sources. Some historical colors have gone extinct as mines have become played out, (the original Venetian Red, Caledonian Brown, Cappagh Brown, and some other ochres were mined until the source was exhausted) but there are still some really great pigments that are not synthetic.

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    I know that Golden Artists Colors has looking into the suitability of MDO board for murals. Here is a link where they mention it

    MDO has also been discussed on MITRA

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    I can see no technical problem with adding stand oil to an alkyd medium to increase body and slow down the drying time. Stand oil is a perfectly stable oil as a paint additive/modifier.

    I do not fbelieve that walnut oil fills are exceedingly weak. It is just that linseed oil films are slightly stronger. Walnut oil is a fine binder with pigments that tend to make good films on their own. Probably it is fine for the whole palette.  I greatly prefer it to poppy and safflower oils for lead white paint.

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    Sorry for not being clear. We just returned for NYC last night and my brain was not up to par. I am not saying that plywood creates greater stresses due to the laminate state just that tensions inherent in the manufacturing means that without a barrier, the grain will telegraph (as you put it) through the ground layers. I believe (but am not positive) that the delamination of plys were a result of impacts to the corners of the artwork executed on plywood. Certainly, hardboard panels are even more sensitive to impacts to the sides and corners so that is a separate issue.  I am also not saying that all plywood panels are equal. Birch plywood is the material that I see most often (ignoring works executed on cheap common plywood) and have seen dozens/hundreds of examples of this checking (or telegraphing). I do suspect that the very nature of plywood would promote this defect to varying degrees with all plywoods but it would require a long term study with different plywood, size layers, grounds, and paint media to make a definitive statement on the subject.

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    Hi Koo.

    I am answering, rather than Kristin, as this position on MITRA originated with myself. It is my view that the stresses inherent in plywood, due to the way in which the plys are created, will very often create checking in the ground over time. I base this on decades of looking as students and professionals who used birch ply and other supposed higher quality plywoods, and simply applied a glue, casein, or acrylic dispersion ground over the sized plywood. So many of these developed checks along the grain lines overtime, often these were visible the first time they were displayed. This subject has been discussed earlier here on MITRA but I see that you commented on the salient thread. Kristin and I were just on a panel at CAA. One of the panelists (Rustin Levenson coauthor if Seeing Through Paintings and owner of three large and busy private conservation firms across the US) showed examples of delamination of individual plys in works that have been in her conservation studios.

    It is certainly true that wooden panels can and do have a host of potential problems, but the above is less the case than warping. I do believe that a canvas interlayer is a smart and possibly integral choice for solid wood panels as well. Now other experts may disagree with my general assessment. The opinion espoused in our resources section and on the forum is based primarily on my long-term observations and conversations with others in the field.

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    ​There are a couple of older MITRA threads that you might find useful (specifically this one here) but try typing "pastel" or "fixative" into our search bar and you will be able to pull up all related threads. Let us know if you have more questions!

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    ​Hi there....not sure if you have had a chance to look at our resources section, but some of the questions you pose above are addressed there (for example in our "Rigid Supports" document that you can find here: Take a look and let us know if you have more questions!

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     I think this application requires a sturdier panel material. ​I have seen boards that thin easily distorted by the force of shrinking fabric or paper.

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    ​I agree with Sarah, I can imagine this material proving adequate as a panel sizing but formulating a "gesso" with an experimental binder would require significant testing. I did locate a blog post by an artist who seems to have tried something similar to what you are proposing:

    Also, a company called "Natural Earth Paint" (mentioned in the above-linked post) apparently sells a ready-mixed cellulose gesso. Maybe you can reach out to these resources and ask if they can share any detals of formulation.

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    ​One possible test that would interest me is the following: if they brushed a little water on a tiny area, do the colors get resaturated? Obviously it would be temporary but it would give a quick read of whether the colors could be revived. We have seen similar "fading" on exterior murals that was reversed with a varnish. The 'fading' in those cases were either a form of efflorescence or chalking, causing an overall dusty pale appearance, which the varnish would undo by being able to encapsulate the solids on the surface. Why it would happen with some of these icons but not others, I don't know, but certainly calcium carbonate has been tied to efflorescence and maybe there is some mechanism at work that is causing that to be driven to the surface. One aspect that might point to something like this - rather than color fading - is that the lightening of the colors seems both even and allover, which speaks to a general surface phenomena and not a pigment specific issue.

    Anyway, perhaps a stretch but something to perhaps try as a way to get more information given the difficulty of diagnosing this from a distance.

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    I really have no answer to this delema. Earth colors would not chemically react in this manner. Perhaps there is some change in surface topography that appears as a change in color but this could only be checked in person. Otherwise, I am stumped.

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    Your alternative recipe would still share the limitations of a traditional chalk gesso, which is only recommended for inflexible supports like panel, and never for stretched canvas as it is far too brittle. Better might be to try using sodium carboxy-methylcellulose  (CMC) as a size directly on the canvas and then use a lean oil ground on top. You might need to experiment with the number of coats you apply to the canvas, and the ratio of the methyl cellulose to water (an 8% solution is a good starting point). CMC is used as a sizing in the textile industry, as well as papermaking, and while often mentioned as an alternative size for people wanting to avoid animal products (as well as PVA/acrylic). I am not aware of long-term studies or conservation research around the use of CMC as a size for oil paintings, so it might still need to be considered experimental, but the conservators on MITRA might be able to chime in on that.

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    ​Koo, these artists are clearly veyr lucky to have you as a consultant/advisor. You have basically covered all of the possible issues that may be the root of the problem when it comes to these slight color changes. Are these photos color corrected? That is a variable that can also through another monkey wrench into the discussion. Honestly, unless we could get some conservators out there to examine the paintings in person and then conduct a preventive survey of the humidity/temperature conditions some of their questions may remain unaswerable for the time being....that being said University of Delaware has a handful of students that would jump at the chance!

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    ​To properly disolve Laropal A81, you will need white spirits (mineral spirits) with at least a 30% aroamatic content. You can prepare a solvent for Laropal A81 by blending white spirits with high flash naphtha or toluene in a ratio of 70% and 30%, respectively.

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    I received this from our resident frame conservator

    In the past, artist’ would use discarded Cedar “Cigar” box lids to paint on, and using Cedar as a substrate for an Icon painting would be fine. It’s general characteristic is clear, straight grain and has a long history of being used in the furniture trades as well building and outdoor uses, fencing and shingles. There are many species of Cedar from around the world and most if not all are stable, some unique characteristics, aromatic as well some having a natural decay resistant properties. The only problem is the size of the Icon to be made and the proper support required and this would depend on the panels thickness as to possible bowing, as one of the problems. Another problem is that this wood is very soft and that distinction “soft” is relevant, any sharp hit the panel might receive over time would be magnified as opposed to using a harder wood. Throughout history Artist’ would use regional native woods but today one can order or travel to a local Lumber Yard, kiln dried, whatever they would like. Oak, Mahogany and even Poplar have been used throughout history as the standard for panel painting, but softwoods such as Pine, Lime, Fir and Fruitwoods all have been used as well, all have their own attributes as well negative physical properties. The choice of Cedar is fine, it is the artist’ preparation of the panel, that is another hurdle.

    Martin Kotler

    Frame Conservator

    Smithsonian American Art Museum

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    I am assuming that George is referring to European poplar and not the American variety known as tulip poplar. That species has no relation to the Old World variety. The closest wood we have to European poplar is cottonwood.

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    Cedar is a softwood which comes from gymnosperm trees. Softwoods are generaly less dense than hardwoods. Medullary rays and tracheids transport water and produce sap. The sap produced by softwoods are known to exude from the wood and can present problems with staining and delaminating paint. Typically, icons were painted only on hardwoods. According to some icon experts, the best wood for icons is lime and cypress. It is worthwhile to note that these two types of wood, although ideal for use in iconography, are not used frequently, since cypress is almost inaccessible and lime is relatively expensive. Therefore, most icon boards are made from less expensive and more easily accessible wood. Poplar is an excellent choice, and it is possible to say that poplar in practice is not inferior to lime and can be successfully used as a material for icon boards.

    Some West European manuscripts of the 17th century provide recipes for treating boards to protect them from insect damage. While these recipes greatly vary, most have in common one substance, garlic juice. Many old icon boards have a dark brown or black color on the back side. Investigations show that these panels were impregnated with substances similar to the recipes mentioned in the manuscripts, and also the brown coloration is due to its being impregnated with drying oil that affords a certain protection from insect attack and atmospheric moisture. Since the first century it was already known that the wood of some trees is not susceptible to insect attacks because of the presence of aromatic substances, which discourage insects. Such types of wood were given preference in panel paintings. It was much later that the back side of icons were frequently coated with oil paint, which besides giving a certain protection from insects, protected board from warping by preventing its one-sided drying. However, this method of protection from warping is not completely effective.

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    Acetic acid would be an issue for the calcium carbonate or sulfate (analogous to Byne’s disease) making it a poor choice for a gesso or chalk ground.

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    We agree with George that most rabbit skin glue sold today is misnamed and is not truly sourced from rabbits but is rather bovine or porcine. These also rarely have the bloom strength of true RSG. However, just on a side note, I do not want to leave the impression that actual rabbit skin glue is only available in Europe. Certainly, genuine RSG is sold in the US - I believe George sells one, and we carry a genuine rabbit skin glue as well (bloom strength 550). So there are sources of RSG domestically although that might not help this particular monk located in Greece

    While not speaking directly to his question, I would also generally recommend the following article as a good overview of the properties of various animal glues, including RSG:

    Animal Glues: A Review of Their Key Properties Relevant to Conservation

    One interesting idea shared in the above, which I have not further researched, is the impact of the fat content in true RSG and its impact of cohesive strength. From pg 61:

    "Although rabbit skin glue has a high gel strength, it has been stated as having lower cohesion and bonding strength than other hide glues [23, 39, 78]. This is thought to be due to its high fat content [9, 23]."

    But if that is a downside, the fat content also imparts some benefits:

    Pg 61: "A high proportion of fat also improves elasticity, although it simultaneously reduces the gel "strength of the glue and final bond strength [23, 84]."

    Pg: 62:  " It has also been suggested that a high fat content, such as in rabbit skin glue, accounts for better stability in moist conditions [5, 39]"

    So, like all things, never quite as simple as one hopes.

    As a final note, generally the lower the gram strength the slower it takes to dry/set and the greater the shrinkage making lower strength glues generally better for cabinet or instrument makers, who generally prefer 120-200 gram strength. Which sounds closer to what he has. Would think something in the 400-500's range would be more preferable for chalk gesso grounds.

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    While I am not an expert in wood, we did end up analyzing a very strange case of discoloration in a painting - especially impacting ultramarine blue - that we were able to trace, with some confidence, to the use of cedar stretcher bars which released acetic acid. See the following article for background in this:

    Because of that experience, we have become very cautious about the use of cedar - and specifically western red cedar - if there is a potential for off-gassing to become concentrated. While cedar might be good for insect resistance, it remains a potential source of acetic acid, which is able to corrode some pigments. That said, I do not know enough to say if this has ever been traced to an issue in egg tempera, and the case we saw was a very particular one that might not be representative of the general risk in using this wood, so please take this as nothing more than sharing a case that surprised all of us.

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    Hi Koo

    I have sent this question to the frame conservator on our board as he is acquainted with the behavior of various woods. I also forwarded it to George O. as he knows a great deal about traditional icon painting.

    I do want to ask if you have any more specific info on what type of cedar? There appears to be many species and they may not all behave in the same manner. I have read that western red cedar works well for icon painting but have no corroboration of that.

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    There are few companies or individuals today (we know of only one in Europe) producing glue from rabbit collagen. The name "rabbit skin glue" is no longer used in commerce to designate the origin of the collagen, but rather the Bloom Strength or Jelly Strength. Rabbit skin glue is now derived from bovine and porcine bones, cartilage and hides with a Bloom Strength of 400 to 450 grams. The term "hide glue" is applied to glue of the same origin of 200 to 300 grams, and "technical gelatin" to glue of 100 to 200 grams Bloom Strength. So, the name rabbit skin glue is synonymous with animal collagen glue of 400 to 450 grams Bloom Strength.

    Since animal collagen glue does not bind the solid particles of a traditional gesso or chalk ground by enveloping them in collagen polymers, but rather forms strong “protein bridges” between particles, it would be important to use a high strength glue. However, the higher the Bloom Strength, the shorter the set time, and is likely why gilders often prefer lower strength glues for gilding, where Bloom Strength is not critical to adhering metal leaf to substrates.

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    ​You can start with the 80:20 ratio, which we have found to be optimum, but you can increase opacity of the mixture by increasing the amount of titanium dioxide. We have found diminshing returns when significantly increasing the amount of tritanium dixoide.

    Lead white by itself usually provides sufficient opacity for most applications, but for brighter highlights you may we try the mixture of the two whites.

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    ​Hi thing to keep in mind is that there is still a lot to be done in terms of testing when it comes to glycol ethers. They can span the gamut when dealing with toxicity....but also this should NOT be considered a binder. It falls under a category of solvents with varying ranges of volatility. So while we cannot speak to issues related to preservation (e.g. yellowing, etc.) here is some more information that follows up on Health and Safety concerns in the AIC News (Vol.8...thanks to MITRA's Health and Safety point person Kerith Koss Shrager for this):

    Some Chemical Things Considered: Glycol ethers and Glymes: Making sense of confusing terminology

    Conservators often work very closely with solvents, so it is important to be informed about their hazards and to stay up-to-date on terminology and naming conventions, in order to recognize which solvents may require more caution. Glycol ethers are a large class of solvents. They may be found in many common household products, including latex paints, paint strippers, household cleaners and detergents, batteries, brake fluid, printing inks, plastics, adhesives, perfumes, and cosmetics. Glycol ethers have historically been used in the conservation field as solvents or diluents in coatings and varnishes, adhesives such as B-72, and solvent mixtures for cleaning. Because of concerns about their safety, the use of glycol ethers in conservation has been reduced over the past 30 years. Glycol ether solvents are used in the ninhydrin test for protein, and the AIC Paper Conservation Catalog ( Paper_Conservation_Catalog) lists a glycol ether as a possible additive in Jade 454 PVA adhesive. Glycol ethers often do not appear on product labels, and may be listed by a confusing variety of names, including chemical names, trivial names, acronyms, and proprietary names. For example, the chemical “ethylene glycol monoethyl ether” may also be known as EEGE, Cellosolve, ethyl Cellosolve, or 2-Ethoxyethanol. While conservators probably know glycol ethers can be dangerous, you might not be familiar with all of the various names by which they may be identified (see table). In particular the name “glyme” has been used recently by the EPA: “glyme” is a trivial name which properly refers only to glycol methyl ethers but is confusingly used by the EPA to also refer to other glycol ethers including diethyl and dibutyl ethers. Of the many glycol ether solvents, only a few have been studied in depth. Several glycol ethers have been found to cause adverse reproductive, developmental, and other health effects. According to the California Department of Health: “Overexposure to glycol ethers can cause anemia...intoxication similar to the effects of alcohol, and irritation of the eyes, nose, or skin. In laboratory animals, low-level exposure to certain glycol ethers can cause birth defects and can damage a male’s sperm and testicles. There is some evidence that workplace exposure can reduce human sperm counts.” Exposure routes may include inhalation of solvent vapors and absorption through the skin; some glycol ethers can penetrate gloves without changing their appearance. Recently, the EPA proposed a Significant New Use Rule (SNUR) related to a list of 14 glycol ethers, which would allow the EPA to evaluate and possibly prohibit the use of these chemicals in consumer products. The EPA has found that while potential exposure to the 14 chemicals is currently limited, there is reason to believe their use might become more common in products including printing inks, paints and coatings, and batteries. The SNUR was issued because of the potential health aic news, May 2013 9 hazards of glycol ethers: “EPA has concerns about the 14 glymes listed in this SNUR, all of which have similar chemical structures. EPA is concerned about the reproductive and/or developmental toxicity of monoglyme, diglyme, and ethylglyme and believes that individuals could suffer adverse effects from their use. In addition, EPA has concerns about the remaining 11 glymes due to the lack of available use, exposure, and toxicity information.” Glymes and glycol ethers have been of concern to conservators for quite some time, and alternatives to the use of glycol ethers in conservation have been discussed for decades, but conservators may still use these chemicals or have older supplies in chemical storage. In 2003, OSHA withdrew its proposed standards on workplace exposure to 2-ethoxyethanol and 2-methoxyethanol and their acetates because there were “few, if any, remaining opportunities for workplace exposure to these glycol ethers.” It is important to keep in mind that conservators often use chemicals in ways and situations that many other workers do not, and therefore government authorities such as OSHA and the EPA are less likely to take common conservation exposures into account when creating regulations. EPA and OSHA regulations may also be delayed by requirements for lengthy congressional hearings. Toxicological data on these chemicals still exists regardless of the status of government regulation, however, and conservators should be aware of other sources for safety information, including the more current 2012 occupational exposure limits established by the American Conference of Governmental Industrial Hygienists. The ACGIH exposure limits for 2-ethoxyethanol and 2-methoxyethanol are extremely low (5.0 ppm and 0.1 ppm, respectively, as an 8-hour time weighted average) as reflects their high toxicity. For additional resources, see the Health and Safety Committee Guide to Technical Resources for the Conservator ( Technical_Resources_for_the_Conservator). Safe working controls are definitely needed for glycol ethers, and conservators should take care to handle these chemicals with precaution.

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    ​A typical ratio of titanium dioxide pigment and extender pigment in commercial oil paint is 20% and 80%, respectively. You can use this ratio as a guideline for mixing basic lead carbonate (lead white) and titanium dioxide (titanium white) pigments for your white.

    Although a rigid panel may place less stress on an oil paint film, lead white also makes an oil paint film less sensitive to water, which titanium dioxide does not do. So, even if you are painitng on a rigid panel, it is still recommended to use lead white in your oil painting.

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    ​I have sent this question to one of out modereators who is up to date on this subject.

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    ​Hi - Let me chime in, especially as Golden is generally the most closely associated with the recommendation of an isolation coat. Essentially any clear continuous gloss acrylic coating that you can apply that works for you will work as an isolation coat. The only reason we recommend using our Soft Gel Gloss is that, by a quirk of its own formulation, it has the best anti-foaming property of any of our products once it is thinned with water to a brushable consistency. Plus the water helps with both flow and leveling. That said, we have had people use any number of alternatives which they have developed their own technique around. So definitely feel free to try other things - just be careful of foam and brushstroke texture, as this is a permanent coating that cannot be reversed. Because of that, we try to stress to people - even with our own Soft Gel recipe - to practice practice practice on less precious pieces or test canvases before using on a finished work that has real value or meaning to you. Like anything, applying an isolation coat, as well as a varnish, is a skill that takes time to master and do well. I say all this because we rarely 'learn' to varnish or apply these types of final coatings while we are learning to paint, so by the time we embark on it, we are usually beginning to show or create work we like and want to protect. On one hand we have spent years honing our skills as a painter, but can forget that we are still a relative beginner when it comes to mastering these types of applications.

    On a final note, I would be cautious and less likely to recommend the use of a flow release. At least in terms of ours, which we recently renamed Wetting Agent, it is a highly concentrated surfactant meant solely to break water tension and used especially when doing staining or working directly on fabrics. It tends to be one of the more misused of our products, and if you decide to try it, you should first thin it 1:10 - 1:20 with water, and then of that diluted mix, add no more than 3% into any blend. Going higher risks generating excessive foam and in our experience, unless you are truly having wetting-out issues related to surface tension, just adds unnecessary complications. If you find you need more flow and leveling, just adding water is usually enough, or opt for a thinner more fluid acrylic medium to begin with.

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    I would not experiment with other media but any high quality acrylic dispersion medium should work. You would want it to flow, so very heavy gels are probably not the best choice. Acrylic dispersion paints are not my forte but I might add a bit of flow releaser (no more than suggested by the manufacturer) to facilitate brushing and flow. I would stay away from matt mediums as they tend to make films that are more permeable.

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    ​Alkyd mediums render the paint fairly resistant to solvents early in the process, so I think with alkyds it's less likely that varnishing the touch-dry picture early will cause the coating to mingle with paints (compared to traditional oils). There is still the chance, however, that dimensional changes in the paint as it cures could affect the varnish layer. That said, I believe the 6-12 month wait is a long-unchallenged  "rule" established before the introduction of synthetic solution varnishes. A.P. Laurie taught that an oil painting should be varnished (with mastic) no sooner than 6 months after completion, and like his often-quoted, similar advice about waiting 6 months to use an oil-primed canvas, while it couldn't hurt, I don't think these rules are based strictly on science. In my studio, I generally proceed with a light coat of varnish when the paint is firm without tackiness, and top-coat later with the same product for a final varnish.

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    ​Regarding the clay, it depends on where you live and what portion of the clay is organic matter which might break down. Some soil has a lovely color when freshly dug due to plant material, but the organic components might not prove durable. Clay that is stained with oxides and ochres will be more reliable over time. As far as the walnut ink is concerned, any vegetable-derived colorant can be vulnerable to color change from exposure to UV light (though anyone who has hulled black walnuts may find it difficult to believe that the stain will ever fade willingly). If I were offering such a piece as you are describing to a collector, I would suggest display under protective glazing, out of direct sunlight or intense illumination, and recommend that the piece be stored at intervals, to reduce total exposure. This is really good advice in general for watercolors where some pigments are not of the highest lightfastness.

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    ​I think most would agree that we artists are a thrifty lot, and we hate waste. I heartily agree with Sarah's suggestion to prime the reverse rather than top-coating the painted side with additional primer. It is, however, worth considering how a potential collector or gallery owner will react to a recycled canvas. Some may find it charming, and others may leverage it to press for a discount. For a commission, especially a formal portrait, I would use only a brand new canvas.

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    ​In general painting new paintings on top of old ones is not a good idea, especially with oils, which get more translucent with age. Plus you end up with a complex sandwich of materials aging in different ways, which just adds a lot of unknown risks.  Oil paintings are complex enough in themselves that adding even more variables to the equation is just not great.

    That said, if it was purely for a study or casual work, you could apply several coats of an acrylic gesso and proceed from there. At least I think that is less complicated than using an oil ground. But be forewarned, in my experience, you simply never know when a study might go astray and have the gall to become something you love and want to keep! Lastly, if it is about saving money, removing the canvas, flipping it over, restretching and applying a fresh size and appropriate ground would be better than directly painting on top of the older painting.

    I am sure others might have other thoughts as well.

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    I understand that modern quarter sawn is generally the best available, but if it can be obtained, rift sawn (what we call radial cut) makes the most dimensionally stable wooden panel.  What you illustrate is probably fine for the size of the panel you are using, however, as both Hugh and I indicated, natural wooden panels are best held into the frame solely in the center at the top and bottom. You method would be fine if you used a very soft foam which would allow a good deal of movement in the panel. Finally, acrylic felt is fine. I was actually referring to felted wool, as I know many people associate the word “felt” with that historical product.

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    A critical factor, here, is what type of panel this is, pressed wood, laminated wood, or solid board, since each will have differing expansion/contraction coefficients.  If it is a solid board, it must be given room to expand across the grain and should be secured at the top and bottom of its grain center, only. That allows it to move, along its outsides, and reduces its chance of cracking. If it is laminated wood, it should be less likely to warp and even spacing all around makes sense. The same is true for pressed wood, but attention should be paid to ensure that its edges (especially its corners) are protected from physical insult, as they can be quite vulnerable.  Volara between the panel’s edges and the frame rabbet, both rabbet width and depth, is a great idea and Volara between the back of the panel and a backing board is also a good idea. The backing board can be made of Vivak (PETG) sheet 00.09” or thicker, which can be screwed into the back of the frame and which will be lighter than plywood and will allow one to see into the back of the frame, to monitor conditions, there.  In short, the plan you describe should work well, for all but solid boards.

    All best,

    Hugh Phibbs


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    That is very unlikely to adhere and even if it did, it could not be burnished to a gloss. Water gilding generally requires an absorbent ground with a water soluble/swellable binder, usually with a bole layer also bound in a water soluble/swellable binder. When burnishing water gilding you are actually burnishing the glue ground and glue containing bole and not the gold. Do to the thinness of the gold leaf,   a layer of finished water gilding can still be whetted with water and additional leafs of gold can be added because of the thinness of the gold and the absorbance of the underlayers. Oil gilding creates a completely water repelling coating that dries very hard.

    It is my understanding that there are modern gilding systems that allow for mirror-like leaf effects using non-glue underlayers. I have no experience with these and cannot comment of the results.

    A search of “gilding” on MITRA will likely reveal additional info on this subject.

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    I will send this to a few experts in the area but as at least one is furloughed at the moment, I will add a few remarks of my own. I hope that someone with greater expertise will weigh in soon.

    Probably what you proposed would work perfectly well for a new painting. However, there are a few considerations to keep in mind when framing or reframing a solid wooden panel. One is to slow the rate at which he panel experiences changes in RH. Museums even go so far as to place the panel within an enclosed envelope. This may be to either maintain (“lock-in”) the humidity conditions when the envelope was created (this is certainly complicated by the fact that RH percentages change with shifts in temperature). A more sophisticated system involves the inclusion of a buffering material (eg silica gel) within the panel envelop. The gel absorbs and releases moisture in response to temperature changes to help maintain a stable RH. This is optimal but entirely impractical for most individuals and galleries.

    Another consideration (which you clearly have thought of) is to make sure that a nonabrasive material is placed/adhered to any part of the frame where the panel touches. Felt has often been used within the rabbet of frames for canvas and wooden panel paintings but would be unappropriated for other objects (eg sulfur in the felt acting on a copper panel, etc). Volara is a reasonable alternative.

    It is also important to not overly restrain the movement of the panel. With changes of RH, wood expands and contracts across the grain (90 degrees to the grain lines. That means that a panel with vertical grain changes dimensions and bows far greater in the horizontal direction that in the vertical direction. In such a situation, we would want to have most of the force holding the panel in the frame at center of the top and bottom of the panel and very little at the left and right edges where the most dimensional change would occur.

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    Let me restate this to be clearer. I am not advocating adding ammonia water to existing artists’ casein paint. I just mentioned my experience.  Ammonia is one of the common alkalis used to put casein into solution.

    Honestly, my earlier comment is not from anything authoritative. In the early 90's I worked with a faux finisher in St Louis. She did all of her undercoats for faux graining using gallons of casein paint made specifically for use for painting theatrical sets. Upon opening the container, you would get a heavy odor of ammonia and the label expressly said to add dilute ammonia to keep the paint from spoiling.

    I do not want to take this any further as I do not even remember the brand of casein paint and cannot really comment beyond that.

    As to the stability of borax vs ammonia casein.  I am going to do a bit more reading on that and perhaps contact Shiva to see if there is really a definitive answer to that question.

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    To answer the query, unfortunately I don't know anything about the interactions of ABS and paint. Aside from Legos, a really common use for ABS is for signs and molded packaging for cosmetics and food packaging (think about the plastic tray holding a sleeve of Oreos). If the plastic is colored, it is typically caused by dyes added to the plastic substrate. 

    In terms of adding a paint layer, I know ABS is very hydrophobic, so acrylics might be problematic. ABS is soluble in some aromatic solvents as well but I have no idea as to the long-term effects. 

    In terms of the stability of ABS, it can certainly yellow, but that depends mainly on light exposure (presumably a paint layer would protect the substrate from yellowing). I'm sure that heat/humidity may also have an effect on the brittleness of the sheet (as with everything). -

    I hope this helps? I know it's not really definitive in any way but this is a rather new substrate that has yet to be tested.

    Alexandra Nichols

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    I have had students volunteer to have their silverpoint drawings placed in a drying oven as well so no shame from me.

    I seem to remember that gallons of casein paints intended for use in theatrical scene painting also contained an excess of ammonia (well beyond the demands of hydrolysis.) to retard purification,

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    Hi Koo -

    Let me jump in here as obviously this is a Golden product and I will be in the best position to answer. See my comments below:

    Is Golden's black gesso high in solids, and/or considered more absorbent than regular acrylic gesso?  

    • We have never used absorbency as a specific metric for these products, so your reporting is really the first time this potential difference was brought to our attention.  In looking into it further, I can report that indeed the Black Gesso does have a higher level of solids. It also uses a different combination of fillers than the White Gesso as obviously relying as heavily on calcium carbonate would cause the black to appear more dark grayish.
    • Unfortunately we have not. On the good side, the Black Gesso should be fairly stable, in terms of physical properties, over its lifetime, and while likely not as unresponsive to changes in humidity as a traditional chalk gesso, the divergence is mostly at higher humidity. See this image from our article on Using Oils With Acrylics as one data point comparing chalk gesso to acrylic paint:

      But until actual testing, it remains a touch of an unknown.

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    I share this only because I found the history of how modern humidity and temperature recommendations came about. For example, this paragraph details how the storage of museum paintings in underground slate quarries in Wales during WWII, which happened to also provide unusually stable environments, really marks the birth of the whole field of how the environment impacts paintings:

    "With the outbreak of the Second World War, mixed collections from the British Museum and the Victoria and Albert museum were removed to quarry storage at 60%RH, 60°F and survived the war in very good condition.[[24]: p.2] The National Gallery's collections were evacuated to storage in the Manod slate quarry, Wales.[[25]] Conditions in the slate caves were a constant 47°F and 95 to 100%RH; brick shelters were built in the caves to house the paintings [[26]] and 'simple heating' was used to control the climate in the shelters to 58%RH, 63°F/17°C with 'exceedingly minor variations.'[21: p.194] Prior to the removal to Manod, a technician had been employed eight months out of every year to deal with cracking and blistering in the panel paintings; during the first year of storage in Wales (1941- 1942), his work reduced to one month and by 1945 he had nothing to do; after the War ended, the paintings were returned to the essentially uncontrolled environment of the National Gallery, and an epidemic of blistering, warping and cracking broke out.[21] This very positive experience of climate-controlled quarry storage contrasted powerfully with the experience of evacuating collections to bomb-proof storage in the tunnels of the London Underground (subway) system during the First World War, when uncontrolled damp had caused serious damage to collections.[[27]]"

    The rest of the document can be found here:

    Development of humidity recommendations in museums and moisture control in buildings


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    Here is what I have been able to find out about this product: "Made from 80% calcium carbonate bonded with a small amount of plastic, this paper can be used with watercolors, acrylics, inks, pastels, pencils, markers, and inkjet printers.

    Yasutomo Mineral Paper can also be embossed, hot-stamped, varnished, glued, and laminated. Water-resistant with a smooth finish, it still has enough tooth and absorption for all mediums. It will not buckle when used with the wettest mediums."

    I have no experience with this "paper" but it it is clearly super-absorbant.  So fingerprints and accumulated dirt and grime will be a problem in the future.  Like any other drawing on a ground... Any uncoated surface needs to be protected.

    Margaret Holbein Ellis

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    ​Framing works on paper under glass does create a micro-climate, which has the effect of slowing fluctuations in temperature and relative humidity within the frame and creating a more stable environment.  That is something to consider.  Overall, I wouldn't worry too much about the low humidity in winter - you clearly care a lot about your art and take good care of it, and as I said it's worse for objects to go through extreme fluctuations than it is to be in fairly steady periods of low humidity.

    We are always happy to answer any questions you might have!

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    At very low humidity, the paper substrate can contract as it loses moisture, which can result in tension between the paper and the media (particularly with heavy applications of media).  Also, some media can become more friable (powdery).  It's certainly not ideal, but the biggest risk occurs if there are dramatic fluctuations in relative humidity, causing an object to expand and contract rapidly and resulting in physical weakness.  I wanted to ask what instrument you're using to read the relative humidity?

    If you do get a humidifier, I would first test it in a room where you don't have any art to make sure that it works without spraying or misting and that it doesn't raise the humidity too rapidly.  I would also only use a household dehumidifier in a large room; in a small space, it may be too much.  An old trick that people used to use in a dry space is to leave a pan (or pans) of water out, which can raise the humidity slightly.  Of course, you have to be careful not to put a pan of water anywhere it can spill and damage your work, and the water would need to be changed regularly.  It probably is also only suitable for a smaller space, but you could try it out and see if it makes any difference at all (it may not).

    To answer your big question, which is how artworks have survived for hundreds of years in various environmental states…there are a lot of different ways to approach this question.  My personal opinion is that materials tend to remain stable when there are fewer fluctuations, even if the temperature and relative humidity aren't ideal.  There are a lot of other factors that affect the longevity of an item, including pH, light, frequency of use, luck, etc.  I also think that when we're looking at artifacts or art made long ago, we are often looking at it in its changed form.  Conservators and collections care staff impose stricter environmental parameters on items because we are trying to keep them as unchanged as possible while they are under our care…but we are aware that this is a nearly impossible task, and that nothing lasts forever.  I don't think any conservator would want you to feel afraid to experiment with your work; it's our jobs to let you know what might happen to the materials you use, but in no way do we want to hinder creativity.

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    Sorry, I meant to add current, general guidelines for works of art on paper are around 59-77°F and a relative humidity between 45-55% (+/- 5%).  For most works on paper it's better to minimize extreme fluctuation than it is to stay within narrowly defined parameters.  Let me know if you have any other questions!

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    Hi Marko -  the environmental situation you're describing is a problem many museums, historic houses, and galleries face.  Conservators and other collections care professionals have been struggling with this and, generally speaking, we've come to the conclusion that the parameters can be set a little bit wider than we originally thought.  Although having strict parameters in place is ideal for some materials (such as certain photographic materials) it's actually more sustainable and more important that there are fewer drastic fluctuations in temperature and relative humidity.

    If you are concerned with the low relative humidity in your apartment when the building's heat is on (something I struggle with in my own apartment, too) you can get a humidifier fairly cheaply.  When you use it, make sure that it's not directly next to any of your paintings or drawings as they can become wet, but placed in the same room can help to bring the relative humidity up a little bit.

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    As oil grounds are, at least initially, more flexible than glue grounds they probably fare better… least in the short term. Again, however, I really do not recommend plywood substrates for oil painting grounds without an interleaf.

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    Matthew, I missed your response. Thanks for your incite.


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    I will respond with a more general answer than just the situation you describe. Probably lamp black is fine in the scenario you describe. However, we often see checking in the blacks in 19th century paintings, even in areas that contain no other layers or pigments. It is difficult to ascribe this to a specific pigment choice.

    Lamp black is a very stable pigment in water based media (although because of its oil nature it is initially difficult to incorporate into the water soluble binder, a bit of ethanol is helpful). It is perfectly lightfast in oily media as well.  Its issues are that it is a very poor drier in oil and it makes, like all of the carbon blacks, a weak oil film. It tends to be more oily and of a smaller particle size than the other carbon blacks which appears to exacerbate the problem. On the other hand, it has been used for hundreds of years and has fared quite well.

    If it were me, I would use a more solid black (like mars) for all but final touches and the darkest darks in oil and reserve the final accents and deepest blacks for applications of lamp black. I understand that this is not an issue in your alla prima painting but just want to get this on record.

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    Also, we are not familiar with any more substantial resources (especially about non-traditional pigments in lime fresco) other than those mentioned.

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    The real color wheel pages are fun and can be useful. Even if they are by one person, they are empirical and not just a regurgitation of what people have read. Thanks Sarah.

    FYI I just checked and the downloadable Kremer catalog does have their list of pigment/medium compatibility including true fresco. It is available in PDF below. BTW, you need to go all the way through it to page 93. 

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    ​Speaking from my own experience as a painter, Lamp Black is better used in mixtures than alone, especially with a film of significant thickness. This color is very slow drying and has a really high oil content. This alone can cause problems, especially if the priming is not very absorbent, and a skin forms over still-soft material underneath. The addition of a naturally siccative color like Raw Umber can help support drying without drastically altering color. 

    In terms of the apparent darkness of Lamp Black compared to Mars Black, some of that has to do with the optical effect of a high proportion of oil vehicle in the former. A good painting medium can serve to deepen the appearance of colors like Mars Black by increasing shine and light penetration.

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    ​Hi Koo -I have also had the same frustration over the years. I will share here what i have often shared with others - keeping in mind that this person's website is....well....Unique? Hard to navigate and find things? A touch crazy? Yes and yes and yes. Plus it reflects only his testing, but I have to admit he has more testing of modern pigments for Buon, Secco and Fresco that I know of or can find elsewhere (Sinopia, Kremer, Natural Pigments). Anyway, Don Jusko's Fresco testing can be entered from all sorts of places and unfolds in all sorts of ways, but perhaps start here:

    And here are some examples of the types of testing you will find:

    Really my only advise on navigating is just to keep clicking through. And again, understand this is one person's test but it might be better than nothing.

    Brian or Kristen might have more solid info but I do have to admit I have a fondness for these types of independent labors of love that you stumble upon.

    Hope that helps.

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    I have seen a rather comprehensive list of historical and modern pigments appropriate for true fresco in Kremer Pigments US catalog.

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    It is really as Matthew says - you will nearly always be fine blending different brands of water-based acrylics. Liquitex's Medium/Varnish has a slightly confusing name - in my opinion - since we often think of varnishes as being reversible and having a unique chemistry. But in this case it truly is simply a version of a water-based medium that they suggest can also be used as a topcoat. But no issues mixing it with other brands that I know of.

    Hope that helps.

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    I have no experience with either of these products. I did take a look at their advertisements and it appears that they are a mixture of calcium carbonate and a synthetic resin. Mitz specifically states 25% non-toxic resin. The idea is certainly interesting but longevity would depend on the stability of the resin and long-term flexibility of the sheet. It would also depend on the normal factors of appropriate absorption, etc.

    We will send your question to some of our moderators/ contacts in the paper and preventive paper/preventive conservation world.

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    I see no reason to believe that Regalrez somehow is exempt from general recommendations about varnish. It is a low molecular weight synthetic resin, which means that it should appear more similar to natural resins as compared to polymers, but that should not exempt it from standard practice. Having written that, I would like to see someone do a real exhaustive reproducible, double blind study on the effects of premature varnishing on oil film strength, solvent sensitivity, etc.

    As to using it as a retouch varnish, if you mean that it could be diluted to a thin consistency so that it can be applied over younger paint films (finger nail test dry) to give some evenness to the sheen before a final varnish could be applied at a later date, it should be fine. If you mean a varnish applied over an incomplete painting to show the true colors AND be overpainted by additional layers of oil paint, that would be a poor idea. Either you would have a very solvent sensitive layer between oil layers which could be undercut during later conservation, or you would pick up the resin with subsequent oil layers making it, in essence, an oil/synthetic resin paint which would be more sensitive to solvents in the long run.

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    As long as the mediums are both acrylic dispersion (water-borne) products, and not acrylic solution (solvent-borne) or vinyl emulsion, in general different brands will be compatible. No manufacturer can test every possible combination with other brands, so there is, I suppose, some possibility of an undesirable interaction, but in my experience, it's immediately apparent when an acrylic mixture fails. One of the other moderators with greater expertise with acrylics will probably be able to explain in more detail.

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    ​Just wanted to add some notes as our GAC 100 was referenced. First, we would not recommend any acrylic medium under a traditional gesso, hide glue/ chalk ground. The adhesion is just not ideal as those grounds really need a very absorbent surface to lock into. So would definitely follow Brian's recommendations on that.

    Second, just to clear up the role of GAC 100 as a "sealer" as it is being too often misunderstood. GAC 100 will NOT 'seal' a panel off from moisture or humidity, which are really the things you want to control. In fact acrylic coatings score quite low in terms of providing an effective barrier to moisture. However, GAC 100 or Gloss Medium are used to block something called Support Induced Discoloration, but that is only a concern for acrylic paints working in specific ways. In your case, having GAC 100 on the sides and back would at most provide a physical barrier, but being as soft as they are, they will also easily become dirty. Instead, if wanting to truly seal a panel from changes in humidity, we would recommend using 2 coats of an exterior alkyd-based wood primer, and if wanting the ultimate moisture seal, follow that with a paint made with aluminum flake. Most major manufacturers such as Sherwin-Williams®, Benjamin Moore®, PPG®, and Rust-oleum® produce these, where they are commonly used for marine, metal, or automotive applications.

    For an excellent list of the coatings with the best ratings for moisture-excluding effectiveness (MEE), we would recommend looking at the table on pages 13-15 in Williams, R. Sam's “Chapter 16: Finishing of Wood”, Wood Handbook, Madison, WI, Forrest Products Laboratory:

    As always hope that helps clarify things.

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    ​Some of the stabilizers/fillers used in this category of oils are borrowed from the food and cosmetics industries (as revealed in patent applications). I've been curious for a while about the long-term performance of these additives, which are different from stearates.

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    ​Yes this is a rather well known article.....unfortunately some of the early conclusions on many things to do with the analysis of binding media are now being revisited (characterization of drying oils being one such topic). So I would not be surprised if a) the authors of the particular study cited in paper retracted some of these conclusions and if b) another lab were test the same painting I am almost certain that a different conclusion would be reached. 
    But the idea that stand oil may possess MORE free, mobile fatty acids vs. cold-pressed linseed is an interesting far as more up-to-date info regarding the precise mechanisms involved with stand oil I found this article to be fairly thorough. However, we still lack the inability to successfully quantify many of these organic markers....of note is the fact that there is no mention of the PIGMENT(S) involved in this study in the WAAC article so I went straight to the source. Of equal interest in terms of blanching for this particular painting is that the pattern was also directly related to presence of red lake, which was either present in lower layers in the underlaying sketch or in visible paint layers. So that throws another monkey wrench into this study (pigments are the true "headache" for those trying to characterize binding media). What would be lovely to have is a nice study that characterizes and quantifies free fatty acids across a range of different drying oils (pigmented and unpigmented) using a number of different techniques....but I am still waiting for that dissertation to show up in my inbox from someone!

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    ​Regarding Geneva paints and their composition....might be worth reading an earlier thread which you can find here.

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    I see no reason to believe that stand oil is more likely to cause fatty acid exudations more than other unprocessed drying oils.

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    ​For now these assumptions are probably good ones. However more time is still needed (and far more research) in order to confirm these theories regarding WM oil films.

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    If you read through our “resources section” and do some relevant searches, you will see that we have discussed most of these issues. Even so, here are a few thoughts: I do not recommend plywood panels for traditional gesso, chalk glue grounds, or acrylic dispersion grounds without some sort of interleaf, preferably of fabric. For 25 years I have seen the surface of panels created by very good craftspeople exhibit checking along the grain with all of these grounds (do a search here to find more discussion of this).

    Additionally, I see no reason to use an acrylic dispersion medium under an animal glue/chalk or calcium sulfide ground. The ground negates any of the stability benefits of the size and creates a situation where the more brittle layer is over the more flexible one. I would size with animal glue if intending on using an animal glue bound ground.

    Please peruse the site but also feel free to ask any additional query on that, or any other, subject if you feel that we have not covered your particular question.

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    I am not sure I understand the process you used to adhere the canvas. When you write, “…I used to fix the edges.” Do you mean that the adhesive was only applied to the very edge of the canvas and panel or was it applied to the whole panel and reverse of the canvas? I would not suggest the former as the adhered portions would react to changes in the environment very differently than sections that were not glued down.

    Either way, likely what happened was that the panel absorbed enough of the adhesive into itself that there was not enough remaining to successfully adhere the canvas.

    As to fixing the problem, Can the canvas be completely removed from the panel? The answer to this will greatly influence how I respond to the question.

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    Thanks Sarah. I would normally just sent the question to you to see if you wanted to respond but thought against it on Christmas day.

    Great info. Silicone release paper or silicone release Mylar are certainly the safest way to wrap a painting if it has to have something touch the surface. We use yards and yards of the SR Mylar in paintings conservation

    As you write, it is always preferable to come up with a system that allows the work to travel and does not touch the painted surface at all.

    Additionally, to the OP, if these simple attempts do not remedy the problem, please advise them to consult a paintings conservator rather than attempt addition DIY methods.

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    Like Brian, these are not situations we would normally advise anyone other than the artist - when willing - to attempt a repair because of the risk of damage. Brian's suggestion of mineral spirits should certainly not harm the painting, although there could always be some change to surface sheen as a result of the initial sticking and removal. If that occurs it can often be rectified with a varnish, but then that itself can alter the aesthetic of the piece and is something to consult the artist on. One word about future wrapping and shipping - we have not had a great track record with glassine and if anything HAD to touch the surface of a painting, we would personally recommend silicone release paper. But ideally, and what is our strongest recommendation, is to pack and store paintings so that no packing material touches the surface. This is possible to do if willing to create a shipping collar that creates a raised edge around the painting that can then support a cover or at least keep any wrapping material up away from the surface. A high-end solution to this can be found on the Canadian Conservation Institute's website:

    And we share a much more casual example in a video that could be suitable for smaller works:

    Hope that helps.

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    They appear to remain sensitive to water even after dry for a substantial time. However, this could be said of other popular paint mediums as well. I also believe that the additives used to make them initially water miscible can migrate. Again, this is not unique to Water miscible oil paints.

    Water miscible oil paints tend to be less fully pigmented than the highest quality ranges and are usually sold as entry-level paints. Therefore, it is probably unfair to compare them to superior oil paints lines that contain no fillers and only the most minimal stabilizers.  

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    ​Sorry to hear this.

    Honestly, these are the type of questions that we generally refuse to answer here. However, your qualifier has made me bend the rules a bit. I am not sure if this will work and I would not suggest anything else DIY.

    I would place the painting face up in a room with good ventilation. With a brush, I would apply odorless mineral spirits to the face of the wrapping paper until it is saturated and transparent. Let is set for a minute of two and see if you can gently remove the paper from the painting surface starting at an edge. If it does begin to lift without damage try to remove the paper at a 180-degree angle so that there is little upwards pull on the painting surface. Stop immediately if you encounter any real resistance. Sorry that is all that I am comfortable suggesting. Perhaps others want to comment.

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    People knew about the relative brittleness of zinc white oil paints for quite a while. Most beleived that this small degree of brittleness was offset by zinc white's more reactive nature in oil allowing for a much stronger paint film than titanium alone. This is also why many in the industry added a small amount of zinc white even to tubes solely labeled titanium white. It was the staple for tints. It is really very recent that we have begun to understand the massive issues caused by zinc carboxylate (soaps) formation and the speed at which these move through a paint film. Even today, only the most forward thinking manufacturers have begun to reformulate their paints based on this research.

    All of these painting handbooks were written before the depth of the zinc soap problem was understood. Of course, Mark's book was the most recent and likely the subject would have been included in subsequent editions if he had not passed away so young.

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    Ron Francis.

    I do think that the Gottsegen book is a far more useful manual, but do understand what you mean. The book is rather "simple" and direct. That is one of the reasons that it functions far better as a general painting manual. However, the first edition contained some info that I missed in the revised edition (for instance how to transform a tube of lead white oil paint into a proper lean lead white oil ground).

    The very comprehensiveness of Mayer's The Artist's Handbook of Materials and Techniques  is also one of its downfalls. Her wrote on everything is an extremely authoritative manner. Some was based on science and testing and other parts on his obvious biases. The truth is that the more you have very strong opinions on, without conclusive evidence, the more you are going to be proved wrong.

    In some ways, especially as a recipe book,  I actually prefer The Materials and Techniques of Painting by Kurt Welte to these volumes. It is also outdated, also very opinionated, and based on the author's general tone, I do not think that I would have cared for him as a teacher, but I find it the most useful of the three as a book of recipes and techniques.

    As to the omission of the problems of zinc white and other contemporary issues, none of this was known when these three authors wrote, so it is unfair to criticize their omissions.  


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    ​Ron PLEASE feel free to post links where ever you wish :)

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    ​ paintings colleagues have forwarded me this interesting chart. While there are no long term studies associated with aging, etc. some of the information may prove useful to some interested in the immediate effects/composition of various dry cleaning products used on easel paintings.Keulen-2012-Drycleaning-table.pdf

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    The answer is obviously very situational but generally, it is important. Transporting paintings in the Spring or Fall and in a moderate temp and RH, may not be a huge issue. Transporting them during the Winter, it is vastly important as the glass transition temp (think the brittleness of painting under the current condition) massively increases at low temps. This is true of both oil and acrylic paintings. Transporting them the hot Summer is also a recipe for disaster. Even appropriate wrapping may not alleviate potential issues. We have seen acrylic paintings and oil paintings with acrylic varnishes with global impressed damage to the surface because the temp was high enough that wrapping materials deformed and stuck to the surface. This is irreparable.  

    Additionally wide fulgurations in temp and RH are most likely when moving the paintings from a stable environment to one that is both uncontrolled and likely more extreme. In short, it is always best to transport any paintings that are important to you any way in a climate controlled vehicle, and it is essential in many situations.

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    ​As long as paintings do not experience sharp fluctuations in temperature and RH in going to and from an exhibition/storage space to the truck/van/etc. AND as long as one remains relatively close to the ideal temp and RH range you should be alright. Actually it is often during transportation that these fluctuations can occur most readily unless the paintings are covered with polyethylene sheeting and properly crated. There are some good references listed in our bibliography at the bottom of this document which you can find in our resources section:

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    I guess I was a little narrow in my response. It just has to be rigid and not corrode in the presence of moisture. Plexi, or even better, ACM should be fine.

    It is also important to not make the paper too wet or you may risk leaching a bit of the sizing out of it. Papers with little or no sizing may react differently and you could change the surface. As these are papers without a design layer, the risk is worth the benefit. This is not the case for paper that already has drawing or other design imagery. One should reach out to a paper conservator in that case.

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    Since you have not started a drawing on the paper, this is relatively easy to fix. This is a far more sensitive problem if there is any applied media. You will need a few of sheet of blotter slightly larger than the paper you are trying to flatten, a glass plate also larger than the paper, some heavy weights (I find large art books a convenient source of weight, and a moister or atomizer that allows for a fine spray.

    Place a sheet of blotter on a clean, smooth, and even surface capable of withstanding heavy weights (the floor may be best if your tables are not substantial). Lightly mist the intended paper with clean water (preferably purified). You will need to do this one sheet at a time or you will require several sets of the aforementioned equipment). Place the second sheet of blotter over the paper, cover this with the glass plate and cover this with heavy books or other weights. Switch out the top blotter after a few hours, and replace this with another the next day. Two days is the shortest time that I would allot before considering the paper stable and flat. This is wholly dependent on the RH of the room in which you are performing the operation. You may need to leave it longer if the environment has a higher RH. If the paper is not completely dry, it will again curl after being removed from under the blotter and weights.

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    I would tend to agree with Matt on this one. However I am posting a couple of links below that do suggest there may be color changes that can occur down the line...The "age" of the Groomstick also appears to matter in the sense that older erasers may tend to leave behind more residues according to this study: check pages 23-25 of this massive document assembled by the paper conservation community some years back:

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    ​So I am posting a link to the Conservation Wiki associated with the American Institute for Conservation (AIC) for works of art on paper. I am presently reaching out to our colleagues in paintings conservation on this matter as I am sure there have been recent studies on this topic as it pertains to the treatment of easel paintings. But here is the link that I mention above:

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    If plasticizers in kneaded erasers could deposit on artwork in significant amounts, in my opinion we would be seeing oil stains while erasing on sensitive papers. According to studies I've seen, among commonly used erasers, kneaded rubber performs best in terms of avoiding particle residue on a fabric surface, better than gum (bread), Pink Pearl, and Vinyl. Kneaded rubber has, however, been shown to cause more color change and alteration of surface on unprotected cotton fabric, but I doubt that's an issue with primed canvas.

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    As to casein grounds, I would suppose that the method used to hydrolyze the casein could have an effect of the patination of the alloy or metal marks. Residual borax may leave an alkaline surface. An undercured ammonia/casein ground may still be offgassing ammonia which could affect patination.

    Having written that, I have only used animal skin glue with pigments and ground silica on paper, a thin pigmented chalk-glue grounds on paper and panel, and pigmented true gesso (gypsum-animal glue) ground on panel.

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    ​I agree, if the paper is sufficiently heavy and composed of high quality fiber content, there should be no technical problem with using it for wet media. In terms of appearance, however, transparent watercolors can look a bit lackluster on unsized paper. Also, the soft, easily embossed surface of some printmaking papers doesn't stand up to the rigors of harder drawing media. A sensitive artist can leverage those properties, though, especially in mixed media where "sparkling" color might not necessarily be the desired effect. The soft, velvety look of watercolor on, say, Stonehenge paper might be perfect in combination with soft pastels and charcoal.

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    That would always depend on the specifics of the situation. The difference between papers intended for dry vs wet media is simple one of weight and sizing. Technically, there is nothing wrong applying wet media on a paper intended for dry media as long as the paper can withstand the weight of the paint and is not so absorbent that too much binder is leached from the paint. You should be able to assess this as soon as the paint is completely dry (do not move the work until it is dry especially if the paper is thin and/or very absorbent). Does the paint readily powder off when touched? Is the paper severely buckled and likely to tear? If not you are probably fine.  

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    ​I cannot speak to that, but have sent this question to Dr. Boon to see if he has any comment.

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    There are a number of ways to approach this that should be successful. What you propose should work fine but I do wonder about the use of watercolor pencils over an oil ground. Likely it would work but why watercolor pencils in this instance. I have fewer issues with the general procedure since it is on a panel but do wonder about the use of slick sealers under oil paint due to the possible reduced absorption and tooth. Perhaps this layer could be micro abraded using a chalk slurry or micromesh to provide a tiny bit of tooth but still have a protective coating over the leaf. Again, very likely this would turn out to be a fine technique.

    However, I do question the use of cheap copper containing leaf. Unless you are working in a larger scale or simply experimenting, it is preferable to use gold (sliver is a separate issue as it tarnishes to a far greater degree than the cheaper substitutes, although they do not possess the same hue and quality). I totally understand if finances preclude this and only mention it because this is a public forum and want to make sure that we mention the relevant issues.  

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    ​Honestly we are also at a bit of a loss here. PERHAPS this has to do with a priming layers that is absorbing your paints unevenly? Can you tell us more about the type of pre-primed canvas you are using? Or is this an acrylic dispersion ground you have applied yourself?

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    ​Regarding India ink, yes, W&N Black Indian Ink is a waterproof, shellac-based formula, as is Higgins #4415. Avoid "fountain pen india ink", which is not waterproof, and may be dye-based rather than pigmented, depending on brand. 

    Sometimes, it is possible to whisk a light watercolor wash over gouache that is very dry, but it quickly wets and intermixes with a second application. It works best when the gouache layer has enough white pigment to quickly draw the water out of the wash without wetting the paint beneath. 

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    Dear Kathy –

    The steps in creating a painting structure that you described below are quite sound. Please do note, however, that Gamblin Solvent-Free Fluid is quite “fat” in nature. Using it to modify the FastMatte colors in the underpainting stage of the painting should be done with moderation (even below the 25% by volume threshold that we recommend). Another good option would be add a small amount of Gamsol to the Solvent-Free Fluid to make it leaner for underpainting. A 50/50 mixture would do the trick. You can move on to straight Solvent-Free Fluid in the subsequent (fatter) stages of the painting.

    Also, just to clarify, our FastMatte Colors are bound in refined linseed oil and alkyd resin, rather than safflower oil.

    Kind regards,

    Scott Gellatly

    Product Manager

    Gamblin Artists Colors

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    ​Your question includes many specific products that I think that it is best to forward it to representatives from the companies that you reference. Hopefully, they will respond in the next few days.

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    In terms of technique, the key difference between gouache and watercolor is whether the source of white in the painting is paint or paper. Depending on the degree of orthodoxy one invests in the process, mixing with white is avoided in transparent watercolor.

    A traditional, transparent watercolor painting is constructed with strategic use of the paper as the source of white which reflects through the paint, preserving the full luminosity of colors. In transparent watercolor, white paint is generally reserved for "heightening" passages, meaning the white paint is used to exceed the brightness of the paper (e.g. reflections on water, glass or metal). Overpainting is limited in transparent watercolor, though beginners sometimes employ a more incremental approach where passages are developed gradually from multiple layers. Experienced painters usually eschew this method in favor of bold, deliberate applications.

    Gouache technique primarily involves mixing colors directly with white paint, though almost all gouache painters also use transparent applications, with thinner layers denoting background, and thicker passages projecting forward. 

    When gouache is layered, darker colors tend to show through lighter ones. This can be frustrating to artists new to the medium, because it limits correction and overpainting, but experienced gouache painters learn to incorporate this property into the process. Gouache is also prone to drying darker than its apparent wet color, but again, this is something the artist masters with experience. Beginners sometimes manage this effect by applying light colors first, and work gradually toward darks. One "cheat" that's strictly for beginners is mixing PVA glue with the paint to reduce intermixing (essentially making a poor-man's vinyl emulsion paint).

    One exciting property of gouache is the difference in body between straight from the tube and diluted with water. Gouache is sticky and ropy from the tube, but becomes creamy when water is added on the palette. By dragging undiluted paint over dry passages, broken impasto-like effects can be created. 20th century illustrators often used this technique to highlight figurative forms. 

    One important factor to consider with gouache is the degree of optical color change induced by fixative. Even a light coating of any sealant or varnish will deepen colors dramatically, irreversibly boosting value contrast well beyond the original appearance. 

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    So I can try to answer a couple of the first questions and possibly question no. 5. First of all gouache was originally opaque watercolor, either opacified via high pigment load or by the addition of certain filles (like chalk for example). More recently gouache has been bound with things like dextrin, which is a modified starch (as well as other possible binders). This is sort of immaterial when it comes to its handling techniques, at least in my opinion. But others might be able to prove me wrong on that one :)

    So for no. 1 it seems in both of these examples that the ink being used is not "co-mingling" with the gouached per say and therefore their different solubilities are not relevant. However, one could use a very standard "India ink" which is generally composed of lamp black bound in a shellac-soap binder. This is not soluble in water and can be purchased in almost all art stores.

    For the rest of your questions it seems that Kristin has already guided you to other relevant threads. Please get back to us after reading these over should you have additional questions. 

    But as for no. 5....Yes I believe gouache can be mixed with acrylic painting. I do not know of any negative long-term effects but perhaps some of our colleagues at Golden can weigh in on this one.
    Brian Baade

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    ​As for type and amount of varnish.....please refer to our advice on varnishing in our Resources section which can be found here. But we feel that a liter for a painting of this size is more than enough.

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    ​In dealing with some of your questions regarding fixatives and framing options, we would refer you to these older MITRA threads here (you may also find more info if you enter terms like "fixative" or "framing" into the search field): 


    As for your specific questions regarding technique I will contact some of the other moderators so that they can hopefully address some of these questions.

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    ​I think a high-density foam roller could yield a good result, if the roller material is designed for use with solvent-borne varnishes.

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    ​Honestly it is not so much WHICH varnish to use (but we will get back to you on that) but HOW to varnish this large format painting. If you must brush varnish ALWAYS start at the top. There will inevitably be drips that appear on the lower half but you can address these as you move down the painting. However many of these issues can be avoided if you use an HPLV spray gun....are you willing/able to do so?

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    ​Damar cross-links as it ages and becomes less soluble in turpentine. If this is a damar varnish layer on a painting of antique age, it might not be wise to attempt removal in the studio.

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    I was unaware of SpectraFix "Degas" Fixative and its inclusion of casein.

    THanks for the info.

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    I cannot say that I have experienced the exact phenomenon that you describe. I have tried to always use higher quality oil paints for anything other than the most trivial color assignments. W & N does freely admit that Winton is their student line but even so, this should not be happening. I generally think of lower grades of paints having greater proportions of fillers and stabilizers that, I would think, could make the pigments less likely to sink and have a surface skin of oil, which would yellow. This could be more than offset by the lower pigmentation inherent in student grades but still this seems surprising, I wonder how you applied the thicker strokes of paint; by brush or palette knife. I have always been struck by how different the surface effects of the same paint appear when using these two different tools. This seems to go beyond the simple smooth surface left by the knife as opposed to the textured artifact of the brush but this is a bit too esoteric for the present discussion.

    Anyway, I am sorry that I cannot give you answers that are more helpful. Hopefully, some of our other moderators can answer with more coherent and cogent remarks.

    Finally, I would say that you should certainly paint over the offending passages with a better quality white, preferably with a highly pigmented, artist grade titanium white. This would likely mean that you would apply a more pigment rich paint over a fatter paint but it is appropriate in this case given the unsightly surface. If it were me, I would lightly abrade the surface of the offending paint with some very fine sandpaper (given that this is titanium white and not lead white or a mixture of titanium and another toxic pigments, ignore this suggestion if this is not the case). 320 or 400 grit should work. This will promote adhesion, which otherwise could have been compromised due to the slick surface skin of yellowed oil.

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    Here is a very good article on this subject by one of our colleagues, Alan Phenix, who worked at the Getty Conservation Institute until recently.

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    ​Just speaking as a studio artist, I think it's important to be mindful of the collector and gallery when presenting artwork. Specifically, I'm thinking of the importance of providing options for maintaining and displaying artwork without the necessity of frequent professional attention. Most artists are familiar with the role of fixative in preventing accidental smudges, and it also has a useful function in preventing particles from depositing on the underside of glazing. So, in my opinion, fixative and glazing are both important elements of professional presentation, where artwork will be offered for sale. I also think when large drawings are offered for sale without glass, it's a good idea to suggest to the collector that frameless presentation should be restricted to short term display, like any delicate work on paper, so deposits of dust and contaminants can be kept to a minimum. 

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    A fixative is by intention and formulation not a good film former.  Fixatives are not designed to "seal" out the atmosphere.  If a continuous coating is desired, a clear acrylic spray liberally applied will go towards your desire to avoid glazing but with serious consequences!  That much acrylic spray - which is essentially a varnish layer -  will have unfortunate aesthetic effects.  The drawing will look like a plastic place mat.  Secondly, there's the problem of application - spraying large drawings using commercial aerosol spray cans inevitably results in uneven accumulations, unless done professionally with spray equipment, i.e., like that used to varnish paintings by conservators.  Finally, that much of a clear coating (a varnish)  on one side of a piece of paper usually has unfortunately effects vis-a-vis future conservation problems.  One side of the paper remains absorbent and responsive to the environment while the other side is encased in acrylic.  Finally, the "varnish" can never be removed - the charcoal particles have become an integral part of it.  In this sense, the varnish is part of the medium - the work is charcoal and acrylic varnish on paper.  In truth, other artists have not solved this problem for large scale drawings.  

    My experience with large scale charcoal drawings in museum collections is that they have been fixed by the artist to the degree necessary to prevent undue smudging.  If direct unencumbered viewing is desired they can be affixed to the gallery walls using rare earth magnets or in some other reversible manner - and then - at the end of the show, taken down and properly stored, i.e., rolled around large acid-free tubes or stored in oversized enclosures.  A frame will only make storage more difficult because the paper is still vulnerable to damage.

    Finally, wax is an interesting (and problematic) medium on paper.  It cannot be considered as protection from the environment.
    Margaret Holbein Ellis

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    The use of a fixative is always a compromise between protection and a change in appearance. The change is most apparent with colored pastels and especially drawings containing white chalk highlights. It is true that a fine spray of a casein fixative have the least effect on the appearance of the charcoal and the paper substrate. Many will not be willing to go through the trouble to make it themselves and since it cannot be stored indefinitely, it is unlikely to be offered by the art material manufacturers. A recipe for a casein based fixative is found in Ralph Mayer's The Artist's Handbook.  I have included it below:

    • Soak ½ ounce fresh casein powder in 4-5 ounces of water for six hours
    • Add pure ammonia drop by drop (about ¼ teaspoon) until the casein has dissolved into a honey-like mass
    • Add 8 ounces of pure grain alcohol (I have used denatured alcohol and it worked just fine)
    • Add enough water to bring the total to 32 ounces and filter before bottling

     It does need to be applied in a fine spray. My experiments with a mouth atomizer were less than satisfactory. One of those affordable aerosol powered sprayers would likely work just fine.

    For those who opt for an off the shelf option, I think that B-72 is probably the best bet. The resin in Lascaux spray fixative was B-72 the last time I checked.

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    If you want to add medium to the pigment, there are a few options to test. Acrylic fixatives, or varnishes can be sprayed on, but they have propellents and solvents to be considered. Degas used skim milk as a fixative and I have been rolling it only watercolors with a sponge roller to see what happens and have found that it evens out the matte areas, but doesn’t change the look too much. Any medium that is added will have some visual effect and must be tested extensively, but I think that casein (which the milk adds) has a good enough track record, historically, to deserve a try. Whether spraying or rolling is used, care must be taken to ensure evenness of coverage, since uneven sealing of the surface will lead to uneven oxidative aging and testing on samples is imperative.
    Hugh Phibbs

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    I am aware of three other suppliers of what appears to be genuine Baltic amber dissolved into a drying oil with and without a solvent. Put amber painting medium into Google and you should find them within a few pages. None are cheap, but these others are less than the brand you mention.

    This sidesteps the idea of whether such a medium is actually historical and if it is beneficial. As to the historical use of such mediums. There are 17th century recipes that mention amber as an ingredient. There is some question as to whether they are actually referring to what we call true amber today. Many believe that a number of resins were called amber at the time. Even the term varnish is related to bernice which is a synonym for amber.  This could suggest that almost any resin cooked into an oil could be called amber varnish or it could suggest a more wide use of true amber containing varnish/mediums. It is certainly true that resins cooked into hot drying oils (linseed, walnut) was the most common form of varnish until at least the 16th century. There an almost mythical respect for the idea of amber varnish in the luthier field, but others poo poo the idea. As to detecting amber in oil paintings, I only know of one study where the Getty found amber markers in paint samples from a work by Orazio Gentileschi.

    To make a hard resin (meaning a resin that is not soluble in any solvent and is only soluble in very hot oil) into an oil varnish you need to heat the resin to a very high temperature as well as heating the oil to close to its flash point. This drives off organic components of the amber and brigs its solubility closer to that of the oil. Thinning with a solvent can only be accomplished after the union of the resin and oil and when the solution has cooled to the point where it would not immediately burst into flame.

    This is a very dangerous operation and should not be done outside of a laboratory or by an experienced operator in a manufacturing facility equipped with full safety equipment. The end product is quite dark and will lower the value and tone of whites and blue colors. It should also be mentioned that the resiliency of the amber is very much altered by the thermal processing and it should not be thought that somehow a dried amber varnish is as impermeable as the source amber.  In fact, even amber is far more sensitive to the environment than most believe. Baltic amber has survived millions of years but generally has done so in the absence of oxygen. Witness the deterioration of the Amber room in the Hermitage because the amber is exposed to the environment.

    However, there is one real benefit to the use of hard resin/oil varnishes over mediums that contain soft resins. When added to oil paint they create paint films that are less sensitive to the solvents that are used to remove old surface varnishes in future conservation treatments. They also contribute a particular drag under the brush and set quickly, allowing for early blending.  I do not believe that amber varnish offers anything above a true hard copal (like Congo copal or Zanzibar copal) varnish. Even this is moot as high quality hard copal mediums and varnishes are as difficult to find as amber mediums/varnishes.

    There are certainly negatives to these hard resin oil mediums as well. These varnishes will darken your paint over time if overused (more than a drop or two added a “blob” of paint. They also contribute brittleness unless the oil component is quite high or the medium is added in only very small amounts. I do not believe claims of them adding flexibility. Show me a study that proves this.

    Full disclosure, when I was more of a practicing painter, I did like to use judicious additions of Congo copal medium to my paint (mixed with a bit of stand oil to counteract brittleness) when I was searching for a particular effect (super fine lines, or to allow for minute and sophisticated blending). I have seen a small degree of lowering of tone in some of my works, certainly not all where I used such a medium, but probably those where I added a bit more than I should have. However, these few examples prove nothing about future longevity as this period of time (15-20 years) is nowhere long enough to predict the long-term preservation.

    So finally, if you are willing to spend a premium and add only very small amounts of a true amber medium to your paint to achieve a particular effect, go ahead. However, alkyd mediums allow for increased transparency, richness, and can accelerate the dry time of oil paint without contributing solvent sensitivity (like soft resins) nor serious brittleness (like all natural resins, when used in large proportions).

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    A beeswax In solvent or bees wax in a solvent/oil/resin medium will contribute great lubricity. It also contributes permanent solvent sensitivity if it is used in more than a very small proportion. If you do this it will probably be best to not varnish your work and you should record your paint and medium ingredients and relative proportions somewhere on your painting (see the resources section for suggestions about how/where to do this). The downside to this is that wax does attract dust if used in larger proportions. However, an oil/wax medium is certainly viable method.

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    We are always happy to share our thoughts and, yes, having this posted on a public forum definitely has advantages as it allows for others to access it as well. Best of luck going forward.

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    Hi - I would be happy to share what we know from our testing and research, which should be applicable to a wide range of professional brands of acrylics. See my notes below:

    1. As I understand there are three mechanisms that enable adhesion of a new layer in a painting:   a) chemical bonding, b) absorption (wetting of the existing surface by the applied layer), and c) mechanical bonding (interlocking with rough/textured areas). Is this accurate? 

    Adhesion is a complex, broad field, so a true listing of all the mechanisms would be a touch longer, but yes, those are the main ones to be concerned about with paint.

    2. When applying the first layer of oil paint over an acrylic primer I assume that there will be no chemical bonding? 

    That is correct. I also think we have a tendency to overestimate the role of chemical bonding in the adhesion of oils on top of oils. At least in terms of durability. Oil is just not a particularly strong adhesive, and while it will form a soft gel on its own, it will not possess strong cohesive forces and the bonds can be easily torn apart. It's not to state that chemical bonding doesn't happen with oils, but I continue to believe that absorption and mechanical adhesion play larger roles than we realize.

    3. Acrylic grounds have calcium carbonate added to promote mechanical bonding. Is this intended to be the primary adhesion mechanism between the first layer of oil paint and the acrylic primer?

    Yes - but, at the same time, for mechanical adhesion to be effective you also need absorption/wetting, and with that comes interactions between the molecules via van der Waals forces. So various mechanisms are still playing a part. I would also want to point out that calcium carbonate plays the same role in a traditional oil ground, which ideally should always be slightly absorbent and toothy as well. Ultimately, I think mechanical adhesion and absorption are playing outsized roles in both systems. After all, how comfortable would any of us feel if we had to start an oil painting onto a very glossy and smooth oil ground. A rougher, matte surface, in the end, provides maximum adhesion in any system - acrylic to acrylic, oil to oil, oil to chalk gesso, oil to acrylic, etc - if only for the increase in surface area and more opportunities for mechanical interlocking.

    4. I've noticed that some brands of acrylic primer tend to be less absorbent than others - as evidenced by less sinking in of the first layer of paint. Also, "non-absorbent" acrylic primer has appeared on the market. It begs the question, what role does absorption play in the bonding of oil paint to acrylic primer?  Can too much absorption rob the oil paint of binder? Can too little absorption limit adhesion? 

    The degree of absorbency will definitely differ between brands based largely of the amount and type of solids being used, as well as the percentage of binder. We are not familiar with any 'non-absorbent' brands and it might be that the phrase is being used more for marketing than anything else. I can share that when a large range of manufacturers helped create the ASTM Standard for Acrylic Dispersion Grounds (aka acrylic gesso) we agreed that a ground had to absorb the oil to some degree and that oil that simply sat on the surface, with little to no penetration, would constitute a failure as much as the other extreme, where the oil quickly traveled through to the canvas. If you are experiencing things being too absorbent you might try adding small amounts of a matte medium to adjust the degree to your liking. Lastly, the number of layers you apply can make a difference. For example see the following article where we show some of this - keeping in mind that the same findings are likely true for any number of companies, but of course always test any brand to make sure you are getting the results you want.

    To answer your other questions, too much absorption can definitely leave a film underbound, chalky, and dead, So not a good thing. As for the opposite, while we have seen repeatedly in our testing that oils can achieve good adhesion even to glossy acrylic films, since at the microscopic level even a smooth acrylic paint layer has innumerable 'worm holes' that oil will penetrate down into, we would never consider this ideal and the adhesion, while possibly adequate depending on your needs, would certainly not be maximized.

    Hope the above is helpful.

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    ​After looking at this website it looks as if the one text mentioned towards the end of the article may be your best resource to date on his acrylic painting technique. I have looked into the public institutions which harbor his works and they are all egg tempera which means that my conservator colleagues will not be able to help answer your question.

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    There is a lot of misinformation about the use of bitumen by the old masters, especially Rembrandt. There is actually, little or no evidence of the use of asphaltum or bitumen in his works. Commentators who mention his use of this material are generally relying on visual evidence (usually based on examining paintings with very old and degraded natural varnishes or extremely outdated "analytical" techniques).

    I just returned from a conference on the conservation of Rembrandt paintings and it is amazing how the appreciation of his work was surrounded by an aesthetic preferring drastically darkened varnishes for literally hundreds of years, starting in the 18th century.

    Bitumen is not a pigment as it is soluble in the solvents and binders into which it is mixed. As such, it is more like a dye that simultaneously functions as a binder. The major issues with bitumen used in oil paint are multifold. First, it remains forever soluble in organic solvents. It will always be disturbed by future cleanings. Second, it loses mass over time and can fissure and fracture into dark unsightly islands often called alligatoring. One can see historical examples of this fissuring where the aperture between islands can be as much as ½ and inch. This can be even more problematic if bitumen is mixed with pigments that do solidify though oxidation and can cause extensive cracking that extends throughout the paint layer and is not just a surface defect.

    The colorant is organic and may fade a bit over time but that is a non-issue compared to the disastrous effects that can happen when using it admixed with oil paint. This can cause global cracking issues.

    There is no doubt that thinned glazes of bitumen are quite beautiful given their golden brown glow. Anyone who had worked with etching zinc and copper plates is familiar with that effect. Much of that results from the fact these layers have no pigment/binder complex and are truly transparent and not simply translucent.

    I generally do not advise to NEVER use a material in painting, but will do so here. If you need this effect, please use bitumen  as a final glaze layer and not as a component of a mixed oil paint application. However, one can very closely emulate the qualities of bitumen glazes by the use of very transparent, modern organic pigments in oil.

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    Thanks so much Matthew and George. I have been at a Rembrandt conference in Amsterdam and have had little chance to check here. You guys are so great to cover these topics so well.

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    ​Magnesium stearate is similar to alumimum stearate in that both are used as pigment stabilizers to mitigate reflocculation and settling of pigments that have been dispersed in oil. Magensiuum stearate is used by several European artist materials manufacturers and appears to be in more common use in the EU, whereas alumimum stearate is more commonly used in North America by artists materials manufacturters. As far as is known today, stearates do not have any siccative action in oil paints.

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    Asphaltum and bitumen are broad terms for a wide range of substances based on high-molecular hydrocarbons. From the viewpoint of current art historical research, bitumen represents a large group of organic substances, which consist of an indefinable mixture of high-molecular hydrocarbons. Bitumen either occurs naturally or is obtained from the synthetic distillation of petroleum. Depending upon its place of origin or technique of manufacturing, bitumen possesses a composition of different characteristics.

    The English term "bitumen" is used to designate a wide variety of hydrocarbon substances, just as pitch is a term used to designate bituminous substances based on petroleum (such as "glance pitch") and substances from the sap of tr