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Artist's rectified turpentine caused white "rings" on my oil painting

Question asked 2021-10-22 01:07:38 ... Most recent comment 2021-10-22 00:09:00
Oil Paint Solvents and Thinners

​Hi MITRA, 20211022_005347.jpg

I began a large oil on linen several years ago, and picked it back up again when I received grant funds to complete the project.

In a case of "what's done is done", since I'd had good luck in the past with cleaning spots/stains off of an in-progress painting with artist's recified turpentine then cleaning off any potential residue with OMS, that was the approach I took earlier this week on one area of this painting. As soon as the solvents dried, I saw a faint white residue that was comprised of many whitish "rings." I had used a freshly-laundered rag that had previously been used for oil painting, so I came back in with another treatment of OMS and a new clean rag, thinking that perhaps a thin veneer of oil that made it through the laundering process had been deposited by the rag. It got a little better (and when the surface was wet with OMS it looked fine), but once the OMS dried, the rings were still there. It kind of looks like a patterned version of sinking in. I wondered if something migrated up, or if I disturbed the binder too much, etc when I cleaned the surface with the turps? 

I use a high-quality paint with a walnut oil binder, so there shouldn't be any impurities in the paint itself. I also follow the fat-over-lean rules, and never adulterate my paint more than 20%. I had started this work with a solvent-based alkyd oil medium, then switched to the walnut alkyd oil medium, though the affected area is comprised of just a couple of layers with the original medium. I do plan to overpaint, though I had been planning to just add highlights and shadows to this region rather than overpaint the entire area -- though if that's what I need to now do, I will. I'm also wondering if varnishing later will take care of it?

I've attached a photograph for your reference. It looks like the whitish shapes settled into texture made by the hand-applied acrylic dispersion primer "gesso", because the paint layers themselves are fairly smooth and applied mechanically thin. (Incidentally, this surface texture is only visible by zooming in on the photo -- it isn't apparent to the naked eye or touch -- and it seems like if the turps bit into the paint layer enough to create the texture, that it would either have revealed the underpainting or the white primer.)

This particular painting is part of a larger project for which I have a deadline. It is a very large canvas, so for both monetary and time reasons, starting over isn't an option. I definitely hope that you won't think it is necessary. 

Thanks in advance for your help and advice. I do hope you'll have good news for me and that this won't cause any adhesion problems down the road. Fingers crossed that it is easily remedied.

Best practice with flexible surface

Question asked 2021-10-04 10:06:41 ... Most recent comment 2021-10-04 12:55:12


The resource guide mentions affixing a backing board to a stretched canvas. How might this be accomplished? If the reason for using a stretched canvas rather than a panel or canvas mounted to a panel, is that the stretched canvas is large and weight is an issue, will the backing panel add weight? Can it be done in pieces as wood that large is not readily available? Does the guide mean to stretch the canvas around the wood and staple it? Or does it mean to glue panels to the back of the canvas?

Non-Rigid Surface oil painting

Question asked 2021-10-04 06:52:55 ... Most recent comment 2021-10-04 12:50:32
Oil Paint
Hello all!

I know it is best practice for oil paintings to be made on a rigid substrate, to reduce the cracking you get with a flexible surface that also reacts to humidity and temperature changes over time. This would include painting on a wood panel, hardboard, aluminium and paperboard, with a well sized and primed surface, with or without a layer of canvas on the top or muslin embedded in a genuine gesso ground.

But, is there anything that can be done to help make a more permanent painting when a rigid substrate cannot be used, as with large paintings where a lightweight surface is required? What is best practice for oil painting on a stretched canvas?

Thank you for any help.

oil paint layers adhesion

Question asked 2021-09-27 19:17:30 ... Most recent comment 2021-09-27 21:39:55
Oil Paint

If an oil painting takes years to complete how does an artist get each layer to stick to the next? You hear a lot about fat-over-lean for working in layers but I haven’t heard much about beading up and adhesion problems with working in layers, I have had to work hard to find information.

I have been building up layers of oil paint on canvas and sometimes find that the paint beads up on the previous layer, especially if I make the new layer oily. If I make it less oily and physically brush it around alot I can usually get it to finally lay on smoothly but I am finding some canvases have poor adhesion and after the layer has dried for a few weeks I can easily scrape parts of the new layer of paint off with my fingernail to expose the layer underneath. But not everywhere, just in some areas. This occurs somewhat with a lower surface layer that has dried for one week but more so with a lower surface layer that has dried for a year.

I haven’t kept track of which oil painting mediums that I used have caused the most problems. I do rinse and dry the surface to remove dust. I don’t want to sand the surface because it seems destructive and would remove part of the painting that I did intend to be there.

So I have quite a few questions about adhesion, if any of you could help me please.

Am I gently scratching too soon, will I find if I wait 6 months that the surface will be harder?

How durable should a dried oil surface be, should I be able to scrape it with a palette knife and it is fine?

Aren’t I supposed to be using fatter paint for upper layers?

What causes the closed off surface? 

What is the polarity I have heard mentioned?

I understand that there needs to be a mechanical bond and a chemical bond but I don’t quite know how that is failing in this case. If I etch the surface will I get a mechanichal bond, but if the surface has oxidised is it too late to get a chemical bond?

I read that you can paint a layer of medium or solvent over the surface to reactivate it, but it hasn’t worked for me. Oil of spike is the strongest solvent I know and it removes well-dried colour but doesn’t seem to ‘etch’ the surface.

I have used a method of applying onion juice to lightly etch the surface and I can see that it changes the surface so that water no longer beads up on the surface and it stops the beading of oil paint and the poor adhesion. Is there anything unsound in this technique? I wash the onion off with water.

I’ve read that using safflower oil makes the poor adhesion of layers worse, is that true?

Are some pigments worse?

Is this surface fragility the same as ‘delamination’?

Thank you for any help!


acrylic over very dried oil

Question asked 2021-09-27 19:04:41 ... Most recent comment 2021-09-27 20:32:50
Oil Paint Grounds / Priming

​I wanted to check something with the experts. I was told a few years ago that an artist was told by a restorer that on very old oil paintings they use acrylic for the repairs. I assume this was done to be a visible repair so as not to pretend to be the original painting. But the artist I was talking to, interpreted this to mean that if the oil is fully dried then you can use acrylic over it.

I wanted to check if a fully dry (2 years or more) oil painting will accept acrylic and create a stable painting. And that leads to someone asking me about putting acrylic primer over an oil painting. She said she thinks it is not a good idea but that all her artist friends assure her it is what they all do to reuse a surface.

Would it make any difference to use the acrylic over a varnish, would it be better or worse?

wet brushes and oil painting

Question asked 2021-09-27 18:26:27 ... Most recent comment 2021-09-27 20:28:30
Oil Paint

​I sometimes wash my brushes, squeeze out the water and continue oil painting. The damp brushes do not interfere with the painting process. But I wondered if a small amount of water would cause problems with longevity later. Does anyone know?

Cadmium Orange

Question asked 2021-09-24 17:24:00 ... Most recent comment 2021-09-25 21:38:22
Pigments Oil Paint

​A very newbie question:  A fellow oil painter asked me if cadmium orange pigment would be brighter than a mix of cadmium yellow and a cadmium bright red.  Bright enough for me perhaps.  It would be rare that I don't tone down the brighter colours, but they want the very brightest orange.   I keep flipping on the absolute certainty of the answer.  It's made from the same stuff.  What I mix looks bright, but then, it will be made from little bits of red and yellow, not little bits of orange.   


Animal Glue & Bloom Strengthr

Question asked 2021-09-19 08:44:55 ... Most recent comment 2021-09-22 05:40:32
Animal Glue

Hello All,

A few questions about animal glues. My understanding is that unless specified as genuine rabbit skin, most animal glues are a mix of animal sources (mostly cow, some pig) and the term "rabbit skin", rather than denoting origin, indicates a quality of glue: high bloom strength and 100% collagen.  My idea of high bloom strength is 450 or so - but I see companies selling so-called "rabbit skin" glues with lower, 350 bloom strengths.  So...

1. Are there industry standards outlining what qualifies as a high enough bloom strength to denote a glue as so-called "rabbit skin"?  

2. If not, what is generally accepted as a high bloom strength?

3. If a glue isn't 100% collagen, what else is it (aside from collagen)?

Thanks if you can offer any insight on these questions! 

Koo Schadler


Question asked 2021-09-19 09:04:00 ... Most recent comment 2021-09-22 05:33:41
Egg Tempera Paint Additives Studio Tools and Tips Pigments

Hello again (second question in one day)...

I want to better understand preservatives used in pigment pastes (helpful in mold prone colors) and egg yolk medium (not something I recommend, as I prefer a fresh egg, but many painters want/need to make medium last longer).

1. Are there benefits to using Phenol (carbolic acid) over alcohol (95% or higher purity) as a preservative?  Alcohol is less noxious than Phenol (I believe, tho' not sure), more readily accessible, and has the added benefit of being a dispersant.  So is there a reason to prefer Phenol to alcohol as a preservative?

2. Phenol and alcohol are volatile.  I would presume that once they evaporate off, they haven't imparted a lasting, preservative benefit to a pigment paste or yolk medium, yes?  Are their preserving qualities present only when the phenol/alcohol itself is present?

3.  Is the moisture within a pigment paste or medium enough to keep phenol/alcohol from volatilizing, or will they volatilize regardless (i.e. even a hydrated pigment paste will lose the phenol/alcohol content over time; hence more preservative must be added for ongoing protection from mold in a paste)?

4.  Given the above, what do you think of the benefit of non-volatilizing preservatives (such as clove oil), if added in very small amounts?  Or is the non-drying nature of this preservative more problematic than its benefit of staying present and thus continually preserving?

A bit in the weeds here, but curious tempera painters want to know...  

Thanks, Koo

House paint as a primer for canvas painting

Question asked 2021-09-19 13:00:03 ... Most recent comment 2021-09-21 22:06:26
Grounds / Priming

I know many artists that use house paint (latex emulsion paint) as a primer for canvas, because they think that the cheaper house paint will work the same as artist acrylic dispersion primer. I point out that house paint is always sloughing off as part of its characteristic of being easily cleaned, that it is designed to last for only 10 years and that a wall is not a flexible surface like a stretched canvas and that the paint in my flat is cracked all over because house paint isn’t flexible. So for those three reasons it is not the same. 

Though I have noticed a big difference in sloughing off between types of paint  - the cheap DIY paint in large buckets that is used in galleries wipes off white on a sponge, which is excellent for removing a stain by removing a layer of paint, but the paint in my bathroom is designed for water and does not scrub off on a sponge when wetted. And I wonder if tougher exterior paint is better.

Some people learned from art school tutors to mix PVA into household emulsion to make a primer. Others use a very good, one coat, stain killer household paint that says it promotes adhesion.

Everyone who uses household paint to prime canvases gets quite defensive and starts saying PVA is PVA, that house paint is the same as acrylic dispersion primer and that artist acrylic dispersion gesso is a rip-off. They say that the wall paint in their house lasts much longer than 10 years and they only re-paint for decorative reasons. 

None of this is about the usage of house paint for aesthetic or conceptual reasons - they all use it for economy. 

Is it correct to say that household latex emulsion paint is not the same as or equivalent to acrylic dispersion primer and that it isn’t a good foundation for permanent paintings? If that's true, can anyone give a clearer picture of how it is different and what problems might arise from using it?

how does solvent affect PVC if it evaporates?

Question asked 2021-09-19 14:03:55 ... Most recent comment 2021-09-20 10:34:05
Oil Paint

I have a fat over lean question.

Does solvent act as a minus of fat (or PVC)? It seems like it does when it is added neat, it thins the paint so it is less fat, spreads it farther on the surface. But it must only temporarily reduce the PVC because as soon as it has evaporated then the ratio is the same as before, right? And when solvent is part of a medium (solvent and oil) then it seems like only the amount of oil matters since the solvent evaporates, you are just adding up the overall oil content of each layer.

Can anyone clarify this?

solvent fat-over-lean question

Question asked 2021-09-20 06:48:48 ... Most recent comment 2021-09-20 10:31:00
Oil Paint

Does solvent act as a minus of fat (or PVC), even though it evaporates? It seems like it does when it is added neat, it thins the paint so it is less fat or concentrated, spreads it farther on the surface. But it only temporarily reduces the PVC because as soon as it has evaporated then the ratio is the same as before, right? And when solvent is part of a medium (solvent and oil) then it seems like only the amount of oil matters since the solvent evaporates, you are just adding up the overall oil content of each layer.

Can anyone clarify this?

Alcohol inks

Question asked 2021-09-07 14:10:47 ... Most recent comment 2021-09-12 19:23:01
Egg Tempera

​hello egg tempera experts! 

I recently bought a pack of waterproof alcohol inks by Jacquard.  

Do you think these are ok to use under an egg tempera painting? As an underpainting? I thought I would experiment with different color ink underpaintings, but I don't want to find out it was a bad idea when it's too late.


Correct way to size fabric with Rabbit Skin Glue?

Question asked 2021-09-04 09:02:20 ... Most recent comment 2021-09-09 13:48:29
Sizes and Adhesives

I can't find a definitive answer for how much RSG is too much or too little. I have been using it while in liquid form, before it cools, and applying with a sponge until it soaks through the back. A friend says that's too much. I do get spots where the fabric is slick and shiny.

I thought to do a light coat on front and light coat on back, but that seems to be not recommended. Is there a better way to do this and still make sure all fibers are saturated? 

Standoil film breaks to aglomerattes

Question asked 2021-09-02 14:54:12 ... Most recent comment 2021-09-08 15:32:55
Drying Oils Oil Paint Paint Mediums

​Dear all,

I painted in multiple oil glazes, first linseed oil and pigment followed by last two or three layers of stand oil and pigment. ​

Stand oil is linseed heated without oxigene and I mix binder and dry pigments prior to painting

The problem happens when I aplly second or third layer of stand oil and pigment, the paint film once brushed equally in few minutes breaks down to aglomerate. It looks like one spills water on horizontal flat surface and then water shrinks to unregular pattern of small shapes. 

It happened when I add solvent and without it.

Why this happens and what could I do to avoid it?

Kind Regards,

Damir P.

Graphene Veils

Question asked 2021-08-27 09:16:48 ... Most recent comment 2021-09-08 08:46:29
Art Conservation Topics

Just wanted to post this as although it's just at the stage of research it's interesting. It's using a thin layer of Graphene to protect artwork from degradation:

Any Specific Gesso Recipes from 16th Century Italy?

Question asked 2021-07-30 20:53:48 ... Most recent comment 2021-08-09 14:05:18


Can someone provide specific gesso recipes used in 16th-century Italy and/or provide resources that might expound upon such recipes? Thank you.

Making changes to a dried oil painting

Question asked 2021-07-30 02:22:02 ... Most recent comment 2021-07-31 22:41:07
Oil Paint

​Hi All,

Periodically I need to make some changes to an already dried oil painting. Usually the painting is only a few weeks old, but sometimes a few months. To date I have either scraped the offending bits off (but this can leave a trough); sanded it off (not sure if this is good for the overall painting) or painted over it with thicker paint (only works where the overlayer is compatible with the rest of the terms of thickness, opacity, etc.).

Would really like to know if there is a better way and, also, what do you think of my 3 methods above?

Thanks in advance,

PS: I usually paint on gessoed canvas panels, although I sometimes use stretched canvases. In the latter case I would usually hold some firm material behind the canvas so that any scraping/sanding did not stretch the canvas in the local area (unfortunatery this dosen't always work and I end up with a localized backwards depression in the canvas).


Paraloid B72

Question asked 2020-10-19 15:44:39 ... Most recent comment 2021-07-30 09:54:23
Egg Tempera


I am planning to use Paraloid B72 on Egg tempera and i have some questions since it will be the first time i will be using it. I am planning to use it on icons painted with fairly high egg yolk content.

1. What percentage should be used for preparing B72 for this kind of paintings?

2. I have read that there are multiple solvents that can be used. Does the polarity of the solvent affect the paintings?. Someone mentioned that non polar solvents have a tendency to cause Fatty acid migration/ foggy spots on paintings. This was mentioned for varnishes that sink into the paintings. How does this apply to the isolation layer produced by B72. I am between using acetone or ethanol.

3. What will be the effects of sealing the paintings if they haven't cured for over a period of 3 months? For example a period between one to two weeks..

Thank you

An oil-based primer that dries quickly and doesn't yellow

Question asked 2021-07-12 09:02:13 ... Most recent comment 2021-07-23 18:10:22
Oil Paint


I have come across an Austrailian brand of oil primer that appears to utilise water-miscable linseed oil because it is dilutable with water. It is fast-drying so that you can apply two coats in one day and paint in oils on the following day, possibly because of alkyd resin content. But since it contains linseed oil I don't understand how it can be applied as they say, with no size. They say this oil primer can be applied directly to the canvas. They also say it doesn't yellow.

Does anyone have any ideas about this?

Testing our Notification System

Question asked 2021-07-14 14:26:49 ... Most recent comment 2021-07-16 14:20:35

Please ignore, i'm tesing our notification sytem


PVA for sizing

Question asked 2021-03-02 13:58:27 ... Most recent comment 2021-07-13 22:06:03
Sizes and Adhesives

Hello all,

I have a question about PVA for linen sizing:

My understanding is that the linen industry has mostly stepped away from using RSG due to its hygroscopic nature and has moved towards PVA for its durability and longevity.  However, I just read that Winsor and Newton advises against PVA for sizing because it will “disintegrate prematurely leaving the remaining painting with no foundations”. Is there research to back up or refute this claim? 

Thank you for any insights you may have.



permanence of oil on commercial oil paper

Question asked 2017-12-13 11:04:29 ... Most recent comment 2021-07-12 16:35:09
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.

Rabbit Skin Glue change

Question asked 2021-07-12 08:51:35 ... Most recent comment 2021-07-12 16:21:06
Oil Paint Sizes and Adhesives

I know lots of oil painters who paint directly on RSG size on linen, with no primer. A frien recently encountered a problem I wanted to ask about.

She prepared many canvasesin her normal way (I do not know the strength of her RSG or how many coats). She used all but one of the canvases. She went back to paint onthe last canvas after one year and found that the oil paint penetrated the size. 

We talked it over and since nothing but the curing time was different we figured that the year of drying had shrunk the size away from the fibres so the seal was no longer complete or even. Does this sound right? It would mean that the layer of oil paint helps stabilise the RSG, perhps sealing it on the one side so there was less surface to react with the humidity in the air. Or does anyone see another possible explanation?

Thank you.

Rabbit Skin Glue change

Question asked 2021-07-12 08:50:53 ... Most recent comment 2021-07-12 08:43:00
Oil Paint Sizes and Adhesives

I know lots of oil painters who paint directly on RSG size on linen, with no primer. A frien recently encountered a problem I wanted to ask about.

She prepared many canvasesin her normal way (I do not know the strength of her RSG or how many coats). She used all but one of the canvases. She went back to paint onthe last canvas after one year and found that the oil paint penetrated the size. 

We talked it over and since nothing but the curing time was different we figured that the year of drying had shrunk the size away from the fibres so the seal was no longer complete or even. Does this sound right? It would mean that the layer of oil paint helps stabilise the RSG, perhps sealing it on the one side so there was less surface to react with the humidity in the air. Or does anyone see another possible explanation?

Thank you.

I spoke too soon. The forum will be back to normal in a few days.

Question asked 2021-06-30 10:52:04 ... Most recent comment 2021-06-30 10:51:00

​I spoke too soon. The forum will be back to normal in a few days.

Egg Tempera - isolator/varnish using Lascaux UV Protect Spray

Question asked 2021-06-23 05:39:50 ... Most recent comment 2021-06-30 10:49:58
Egg Tempera Varnishes Matting, Framing, and Glazing

​How quickly can one apply a spray isolator/varnish such as Lascaux UV Protect spray over an egg tempera painting?  See: One specialist art supplier in the UK suggested it could be applied as soon as the ET surface was dry as it mainly evaporated on contact.  I have made some test panels and find it works well as an isolator or finishing varnish, even after a few days when the paint is relatively fresh, but touch dry.  I have seen some previous forum entries suggesting a longer curing time is recommended (6 months or longer) but provided there are no immediate visible problems (such as uneven sinking in - which I haven't found an issue, even after isolating after a few days) are there other potential problems that could arise later on?  Of all the various preparations/combinations I have experimented with, Lascaux is the one preparation which is nicely matt​/does not sink in.  I have tried A82/Regalrez/Golden products in various ways and they are either too uneven or have an unsatisfactory high gloss/slightly plastic appearance.  I don't always have the time to wait 3-6 months which probably explains why insufficient curing is probably the cause of my issues with uneven sinking in etc - and which is why I favour Lascaux.​

On another note, if I decide alternatively to place an ET painting behind glass, which has been my practice so far, when is the earliest I can safely do so - obviously the framer will take precautions by insterting slip/beading between painting & glass.  Is it OK to fully seal the back or can one allow breathability & air circulation ​by not taping up..?  

Thank you for any advice. Zarina

Recent problems with MITRA

Question asked 2021-06-26 23:21:23 ... Most recent comment 2021-06-26 23:20:00

​Hi all. UD was doing routine server work and it caused some glitches in a number of associated webpages. I would have warned everyone, but I learned after the fact and the site was not working, making it impossible for me to post about the problem. We now appear to be out of the water on this. I look forward to continuing our dialog about art and materials and techniques.

Egg Tempera on Parchment

Question asked 2021-05-24 09:37:25 ... Most recent comment 2021-06-18 14:56:47
Animal Glue Art Conservation Topics Egg Tempera Flexible Supports Gouache Rigid Supports

I once painted an illuminated image on vellum, mostly in ink and gouache, but with a small area in egg tempera.  Within a season the skin had warped, the tempera section had cracked and, in parts, delaminated (image attached, in raking light). KS ET on Vellum.jpeg  The pigment involved in the delaminated area – genuine lapis lazuli – no doubt (due to large particle size and rigidity) exacerbated the inherent problem of an inflexible medium on top of a hygroscopic, moving support.  

1.  Medieval manuscripts are often said to be painted in "tempera".  How many are actually "egg tempera" versus simply a water-based "tempera paint" (gouache)?  Is the same, somewhat confusing terminology that is seen in early Egyptian art (i.e. many images labeld "tempera" are not egg tempera) applied to manuscript illumination? 

2. If manuscript illuminations are, in fact, egg tempera, how have them been preserved?  Were they thinnly painted?  Is the binding of a manuscript enough to keep them stable? Or, in fact, have egg tempera illuminations suffered more than images done in goauche or watercolor?

3. Any thoughts on adhering animal skins to rigid substrates?  The facts of egg tempera (a high PVC paint that gets more brittle with age) combined with practical experience tells me animal skin supports and tempera are a problematic combination. Given how water-loving and strong animal skins are, would adhering them to a rigid support resolve the problem? Or exacerbate it (since skins and wood expand/contract at different rates = lots of stress in the artwork)?  If not on a wood support, how about vellum on other substrates (paperboard, ACM, plastic)?

Any thoughts on the above are most welcome!  Thanks, Koo Schadler

Tubed Tempera, Mysterious Craquelure, Venus

Question asked 2021-06-18 14:54:06 ... Most recent comment 2021-06-18 14:26:00
Egg Tempera

1.   Zecchi's tubed egg tempera paints are made from pigment, freeze-dried egg yolk, gum arabic, and preservative.   

- Any thoughts on freeze-dried yolk as a binder? 

- What would be the reason to combine yolk and gum Arabic binders in a single paint?

2.  Mysterious Craquelure.  Tempera painters occasionally report a mysterious ‘craquelure’ that appears in the uppermost layers of tempera paint during the painting process.  It starts out as barely visible lines that gradually increase with successive layers; as more paint is applied, lines coalesce into a network of minute cracks, and can eventually cause paint to flake and delaminate.  It’s seemingly associated with well-developed areas (lots of underlying layers), and generally involves titanium white.  I don’t know what causes this, I can only offer tentative explanation, among them:

 a. Underbound, very diluted paint.  When too much water is added, at some point the various components become so separate, binder so attenuated that the resulting paint film is friable and under bound.

 b. Over saturating underlying paint layers with water. Studies of solvents applied to ET indicate that spirit-based solvents  leach lipids; water seems to induce swelling in the paint film.  If a curing film is compelled to repeatedly expand and shrink, the stress could weaken bonds being formed in the polymerization process, and result in cracks.  

There is also the speculation that, in an over saturated surface, excess moisture might draw yolk binder downward so that upper layers become under bound and fragile.  This latter theory doesn't seem as likely to me, but could it be possible?

c. Poorly dispersed titanium. TW’s fine particle size tends to clump together, and needs to be carefully and thoroughly dispersed - yet I often see students give it cursory attention with the palette knife.  So, perhaps aggregate clumps of poorly dispersed titanium contribute to cracking? 

I favor explanation ‘b’- because of the circumstances and solution to the mysterious craquelure I experienced a few times in my early painting days. It generally occurred when I worked very rapidly, quickly piled up layers, and thus also accumulated lots of water within the paint film down to the gesso.  To fix the problem, whenever I build many layers in a short amount of time, I continually and thoroughly dry underlying layers.   Since adopting these work habits, I haven’t experienced “mysterious craquelure”. 

Any thoughts would be appreciated!

Damage to traditional gesso surface

Question asked 2020-06-25 11:16:14 ... Most recent comment 2021-06-17 23:24:01
Rigid Supports Art Conservation Topics Egg Tempera Grounds / Priming

Hi! I have damage to the surfaces of some traditional gesso panels I made: traditional gesso on muslin on Baltic birch ply. The surfaces have been damaged. In some cases the muslin fabric below the gesso has been exposed. In other cases, I hesitate to sand away scratches in case of exposing more fabric. My understanding is that gesso layers should be applied while just dry to the touch, and not after the layers have cured, as is the case with my panels. Any advice on the possibility of repair would be much appreciated. They will be used for egg tempera, so surface aberrations are unfortunate given the thin nature of tempera. Thank you!

Tubed Egg Tempera, Freezing Egg Yolk

Question asked 2021-06-17 16:23:02 ... Most recent comment 2021-06-17 16:15:00
Egg Tempera

I'm trying to better understand a commercially produced, tubed egg tempera paint made from pigment, freeze-dried egg yolk, gum arabic, and preservative.  Freezing egg yolks (as discussed on various cooking forums) seems to be acceptable if there are additives (sugar, salt); otherwise freezing seems to break the yolk's natural emulsion.  Any thoughts on freeze-dried yolk as a binder?   Thanks, Koo 

I am back

Question asked 2021-06-04 14:30:45 ... Most recent comment 2021-06-04 14:30:00

​Thank you other moderators for filling in for my in the last two weeks.

Multimedia Artboard

Question asked 2021-06-01 08:29:25 ... Most recent comment 2021-06-04 08:48:53
Rigid Supports Oil Paint Art Conservation Topics

​They claim this material is archival. Is it?

ABS plastic panel

Question asked 2021-06-01 08:32:33 ... Most recent comment 2021-06-03 16:48:06
Art Conservation Topics Oil Paint Rigid Supports

​Is this a suitable archival support for permanent art?

Fire retardant over acrylic and acrylic spray paint

Question asked 2021-06-02 16:18:58 ... Most recent comment 2021-06-02 18:29:02
Acrylic Health and Safety

I have been asked to cover some finished paintings with fire retardant. The paintings are acrylic and acrylic spray paint on maple plywood. Is this going to ruin the paintings?

Signing an oil painting

Question asked 2021-05-31 15:41:24 ... Most recent comment 2021-06-01 20:33:03
Oil Paint Studio Tools and Tips Pen

​Need suggestions for a commercial quill or penlike vehicle to hold medium viscosity oil for signing oil paiantings OR

Is there an italic Sharpie like product whith which it is OK to sign an oil paiinting? Small brushes too broad, too many bristles.

Water Gilding

Question asked 2021-05-28 07:05:20 ... Most recent comment 2021-05-30 07:43:53

​Hello everyone,

I was wondering if there are any recipies for making my own Gilders clay bole from scratch? 

I read the post about the 19th century gilders clay bole,but information is missing..

Thank you

Fat Over Lean & Adding Mediums; Same over same

Question asked 2021-05-24 13:25:20 ... Most recent comment 2021-05-26 21:15:03
Oil Paint

​I'm sure this has been addressed here ad nauseum and don't wish to create more work for anyone.  Can you please direct me to a resource that can educate me on the use of mediums and whether mediums that speed drying are considered fat?

I paint in layers without solvents and am currently using Gamblin's Solvent-Free Gel and Medium, both of which contain safflower oil and alkyd resin.  These mediums speed drying somewhat over using the paint neat.

I have read two conflicting viewpoints over whether the addition of mediums increases fatness.  One opinion is that the addition of any extra oil medium, regardless of whether it speeds drying time, increases fatness.  The opposing viewpoint is that any medium that speeds drying has also increased leanness.

I'm not sure how to think of this. 

Finally, does painting "same over same," as one might do when applying paint from the same brand without adding any mediums or other additives, violate the fat-over-lean rule?

Thank you!

I will be away from MITRA until the 1st. Brian Baade

Question asked 2021-05-25 18:41:11 ... Most recent comment 2021-05-25 18:38:00

​Hi all

I have been hard at work preparing my initial documents for tenure. This is the reason that I have not responded much the past week. I am going to focus solely on this until the 1st of JUne. I see that the rest of the moderators, especially Matthew,  have been doing a great job and I look forward to returning to posting on a regular basis.

Oil Sticks - does the wax cause problems?

Question asked 2021-05-24 13:11:09 ... Most recent comment 2021-05-25 15:15:59
Oil Paint

​I am presently creating oil paintings using oil sticks and oil paints. I create my first layer using Shiva Oil Sticks, which have a matte finish and dry to the touch in less than 24 hours.  My second layer consists of Sennelier Oil Sticks, which are much oilier than the Shivas.  My final layer is completed using Gamblin Oil paints applied neat.

I've read elsewhere that oil sticks are not as compatible with regular oil paints and do not dry as well as or create as strong a film as regular oil paints, which can lead to problems down the road.  

What are your thoughts on this?  Thank you!

Tempered Hardboard - painting directly on it with oils

Question asked 2021-05-15 01:54:18 ... Most recent comment 2021-05-25 10:10:57
Rigid Supports Grounds / Priming Oil Paint

​Hi.  I'm a bit confused about tempered hardboard and whether it's considered to be an archival support for oils.  Can I paint directly on it without any prep at all, including skipping adding any oil ground?

I posed this question to one of the popular oil paint companies and was told that I could paint directly on the hardboard because there's little risk of the board absorbing either moisture from the atmosphere or oil from the paint, so there's little risk of warping or movement from moisture, or degradation from the oils.

One of the popular acrylic paint companies suggests 2 coats of gloss medium followed by acrylic gesso.  I know there's debate over whether painting oils over acrylic sizing and ground is archival.

What are your thoughts of these issues and do you recommend painting oils directly on tempered hardboard with no sizing or ground at all?

Thank you.

Egg Tempera Varnish Clarifications

Question asked 2021-05-15 10:25:59 ... Most recent comment 2021-05-23 07:35:58
Egg Tempera Varnishes


I am updating the section in my egg tempera book on varnishing.  It's a very complicated chapter, unfortuantely, because it's an unfamiliar subject to many tempera artists, so there's a lot to explain; and there's the added complication of so many potential products (both as isolators and final varnishes).  Of course I can't cover every product, I discuss what's most recommended and ones I'm familiar with - still, it's a challenge to organize and make coherent.

Given the above, I'm trying to get the right nomenclature to distinguish between water-based synthetic polymers (primarily various Golden products, although I also include water-based PVAs offered by Gamblin and Talas) and solvent-based synthetic polymer resins (B72, Mowilith 20, Soluvar, MSA, Laropal, Regalrez).  So my questions are..

- Are both water-based and solvent-based synthetic polymers considered resins, or is the term "resin" associated only with solvent-based coatings?  Is there a reason to distinguish solvent-based synthetic polymers as "resins" (does it contribute anything to understanding that group of coatings)?

- B72, Soluvar and MSA are HMW, yes?

- B72 is soluble in acetone, toluene and xylene; Soluvar and MSA soluble only in true mineral spirits, yes?

- Laropal and Regalrez are LMW, yes? 

- Both Laropal and Regalrex are soluble in either true mineral spirits or OMS?

- Is it important to include the numbers in Laropal A81 and Regalrez 1094?  I'm sure they're meaningful, but it's already confusing for newcomers to absorb these strange (to them) chemical terms, and lengthening their names with meaningless (to a newcomer) numbers can make eyes glaze over... 

I know MITRA has an excellent section on varnishes - I'm including the link in my book.


Koo Schadler 

Student Grade paint

Question asked 2021-05-15 05:14:57 ... Most recent comment 2021-05-23 03:06:09
Acrylic Art Conservation Topics Oil Paint Scientific Analysis Technical Art History

I have the perception (whether right or wrong) that Student Grade oil paint from the main manufacturers contains an abundance of fillers and that these make cause long term problems with the paint film (aluminium stearates, etc..) compared to the use of Artist Grade oil paint.

I also have the perception that Student Grade acrylic paint (from a good manufacturer) does not have the same issues as the acrylic paint film is much more stable over time.

Am I wrong in these beliefs?


oil painting on stone veneer

Question asked 2021-05-18 14:51:13 ... Most recent comment 2021-05-19 17:03:53
Industrial and Non-Traditional Products Sizes and Adhesives

I have found a stone veneer product that I would like to paint in oils on.  It is very thin and has a backing that consists of an adhesive  ( that has a PH of 3.5- 4) and cotton.  The company has said to me that the PH needs to be this in order for the product to be waterproof. .  So my question (s) is this:  Is this a bad idea and if so, can it be fixed?  ( Example, could I use buffermount to adhere the backing to an archival board say?  Could I paint some type of ground on the stone's surface to  seal it/ give it more protection?   I really want to work on this because it is super lightweight, pliable and I have lots of ideas.

silicone paper

Question asked 2021-04-29 10:26:15 ... Most recent comment 2021-05-19 09:48:41
Industrial and Non-Traditional Products Handling and Transportation Art Conservation Topics Storage

​I have another question for you experts:

I am looking for silicone paper, for wrapping art. But it's hard to come by, and expensive. Unless you could use silicone paper used for the food industry. Then it suddenly is very affordable and relatively easy to get.

Do you people know if it's the same product? Is it safe to use foodgrade silicone paper for art?

Wax Mediums

Question asked 2021-05-15 18:49:47 ... Most recent comment 2021-05-16 07:18:23
Encaustic Varnishes

​A few questions about wax mediums.

1. Most wax mediums have some sort of resin and solvent.  Does anyone know if Renaissance Wax contains a resin (its ingredients are listed as microcrystalline waxes & mineral spirits)?  If not, what causes it to harden; is it just the inherent hardness of the mix of petroleum based waxes in it, once the solvent content has evaporated?

2. Dorland's Wax Medium is made from beeswax, paraffin, microcrystalline wax, dammar; it does not list its solvent content in the ingredient list, just says "can be thinned with turpentine or mineral spirits".  Yet other places on the web say it can be thinned with OMS.  Anyone know it's solvent content?

3. Are microcrystalline waxes (no color, harder) preferrable to bees wax, or are they equally good?

4. Can solvent-based wax mediums be applied on top of water-based synthetic polymer isolators (such as a PVA, GAC 500, etc)?

5. I presume that for a wax medium to go on top of a solvent-based isolator, it must contain a different solvent from whatever went into the isolating coat; otherwise applying the wax medium would dissovle the underlying isolator - yes?

6. Has anyone tried the Williamsburg wax medium, which is solvent free, as a finishing layer?  If so, any thoughts on its appearance, drying time, etc.?

7. Finally, if George O'Hanlon at Natural Pigmetns could clarify the practical differences between his two wax mediums (Rublev Wax Medium [beeswax, dammar, odorless mineral spirits - Rublesol, I presume?] and Conservar Wax Medium [microcrystalline wax, aldehyde resin, mineral spirits], that would be most helpful.

Thanks! Koo Schadler

Oil Paint on Convex and Concave Solid 22kt Gold

Question asked 2021-05-01 10:14:21 ... Most recent comment 2021-05-15 05:20:45
Rigid Supports Gilding Oil Paint Grounds / Priming

Hi, I'd really appreciate some advice on an unusual query; I've been referred to this amazing website through the Painting Best Practices Group on Facebook. I've had a good look through the resources and forum threads on here, but I still have some questions:

I’ve been asked by a jewellery designer if I could paint miniatures in oil paint onto slightly concave 22ct gold ovals, circa 1mm thick, to be set into a bracelet. I’m wondering what a concave surface will do to the paint layers over time.

I’ve previously painted on convex gold domes for the same client, treating it like painting on copper/on top of gold leaf (there was limited testing I could do on solid 22ct gold!): the gold was completely obscured, as it was purely to make sure the whole jewellery piece was made of precious materials. I very lightly abraded the gold, degreased it with denatured alcohol, then two thin coats of a flexible primer: Liquitex clear gesso primer (chosen because it was difficult to scrape off copper that had been prepared in the same way. It was also quite difficult to remove from the gold dome two months down the line, i.e didn't peel, when I removed the finished painting to make way for a new design). I then painted in very thin layers using the minimum amount of medium: progressively fatter turps and linseed oil. The final paint thickness is very thin. 6 months on, the convex domes appear unchanged (if 6 months is a reasonable cure time? I’m expecting the cure time to be slow because of the circa 1mm thick metal support, but it is very thinly painted).

For the concave domes, I’d be using the same process and medium.

- Is a concave surface inherently unsafe for indirect oil painting?

- If not, would an alkyd primer, or a lead-based primer be a better product than the acrylic gesso primer? I'm working on the assumption that the gold is largely chemically inert, with circa 2% copper and circa 6% silver - I gather lead primers bind chemically to copper, but my only option (as I'm in the UK and lead products have been phased out) is an old tube of Daler Georgian Flake White – it doesn’t say if it contains zinc, or if it’s linseed oil. I don’t know if this would be up to snuff as a priming layer at all.

Thank you for reading this long-winded post!

Muller vs. Mortar/Pestle

Question asked 2021-05-12 07:55:59 ... Most recent comment 2021-05-14 06:44:26
Pigments Studio Tools and Tips

Most pigments come ground to optimal size, but occasionally an historic or earth pigment (anything larger than about 40 microns) benefits from a bit of grinding.  A glass muller (about 5.5 Mohs - yes?) isn't necessarily hard enough for grinding (depending, of course, on the hardness of the pigment being ground), nor does a muller's shape direct force in such a way as to grind effectively (rather, its flat bottom shape seems best suited to dispersing pigments).  So a mortar and pestle seems a much better tool for grinding (and the harder the material it's made from, the better; i.e. agate, porcelain).  Yet I see mullers often discussed or even recommended for grinding pigments.  

Is a muller suitable for grinding (I think of mullers as primarily suited for dispersing)?  Is a mortar/pestle unquestionably preferable?  Is any substance added to the base of muller to increase its hardness?  Any other thoughts?  Thanks.

Pva on raw unprimed linen problem

Question asked 2017-11-25 11:39:09 ... Most recent comment 2021-05-12 10:34:32
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.     



Oil strikethrough on linen

Question asked 2021-05-11 08:33:39 ... Most recent comment 2021-05-12 08:00:33
Grounds / Priming Drying Oils Animal Glue Flexible Supports Oil Paint Sizes and Adhesives


I commonly paint on a good quality, heavy cotton duck (on stretchers) which I paint on unprimed. I size the canvas with three coatings of fairly dilute rabbit skin glue (1:20 ratio) and paint straight on top. I have been doing this for several years, and my usual test of whether the size is sufficient to protect the cotton from the linseed oil in the paint is to check for strikethrough on the back of the canvas - usually my sizing method prevents any strikethrough, and seems successful. I'm also careful not to create a thick 'layer' of rabbit skin glue, as I'm aware that this can cause problems of delamination and animal glues in general are a bit vulnerable to the environment. I look for a very slight glittering on the surface of the cotton to judge that the size is going to be effective.

For my most recent project I decided to switch to linen. I have what I think is a good quality linen, but when I've stretched and sized it according to my normal method, I'm getting some quite bad results. There is a lot of oil strikethrough happening. I believe that the oil is actually going through the holes in the linen's weave, and then soaking into the back side, since the weave seems rather loose compared to the cotton I usually use, and I can see pinprick holes. My plan to remedy this issue (on the canvasses I haven't already started painting) is to add another layer of rabbit skin glue, at twice the usual strength, and attempt to have the glue size 'plug' the holes in the weave and therefore prevent paint getting through (so basically the usual job of a primer). Adding a layer of primer isn't an option because I already have a detailed sketch on the canvas and need my ground to be transparent so I can see it.

Is this an acceptable strategy to mitigate this problem? Is there anything I can do to my initial layers of oil paint to minimise strikethrough? Adding solvent seems to make it worse, as the resulting thinner paint finds its way through the weave even more readily. I have also been considering relaxing the tension by moving the staples, while the linen is wet with glue, in the hope that when it dries and re-tensions the weave won't be quite so 'stretched'.

I've been reading a bit about the debate over how disastrous strikethrough really is, and it seems a little ambiguous. I'm not sure if accepting the strikethrough is a better bet than experimenting with a thicker size layer? Of course I'm aware that I might end up with oil sinking later on and have to deal with that, but my main concern now is ensuring a stable foundation.

Combine sealing an ink drawing with imprimatura on gessoed panes

Question asked 2021-05-06 13:16:10 ... Most recent comment 2021-05-06 21:21:33

With my intent to paint alla prima using Liquin Original medium with oil paint on Ampersand Gessobord, are there any problems combining OMS with Liquin Original and including an oil color to seal the India ink and tone the panel?

Nonremovable Varnish for Acrylic Painting

Question asked 2021-05-04 12:02:28 ... Most recent comment 2021-05-04 19:39:38
Acrylic Varnishes

I want to use a nonremovable varnish for my acrylic paintings. I don't want the fuss of applying an isolation coat, and I am just a hobby painter, so I am not worried about any of my paintings ever needing to be conserved in the future, or having to remove the varnish. I am looking for a layer that provides UV protection, a unified sheen, a protective layer against dust, and a surface that I can clean dust off of. Because my work is textured, I want a spray application, and I don't own or want to acquire a paint gun or an airbrush, so I want a spray can. I also want a low odor and low fume product. I have read about Liquitex Spray Varnish, and I have seen an ad for Krylon Crystal Clear. Are these good products? Is Krylon ok to use on fine art? Are there any other brands you can recommend? Thank you.​

Seeking clarification about tooth

Question asked 2021-05-03 12:11:48 ... Most recent comment 2021-05-04 12:44:54
Grounds / Priming Oil Paint

Hi everyone, I was hoping to gain some clarification about tooth with regards to acrylic "gesso". I primed some canvases last week with Golden's acrylic gesso and am currently waiting a week for them to be fully dry. I have also been reading several commenters saying the surface is slick and not toothy enough for their liking with this brand (however most painter's I've asked swear by it, so I don't know if that's a common complaint). 

On Justpaint they had this line that intrigued me: “A toothy surface has adequate micro-texture to allow a subsequent coating to physically conform to that texture.” Is that suggesting that tooth is on a microscopic level and not necessarily a tactile observation? Could a gesso be slick to the touch, but actually microscopically mechanically bind? 

Or is it a little bit of both, like could a very textured-in-application but lower quality acrylic gesso make up somewhat for the lack of microscopic adhesion. 

I hope what I'm asking makes sense! 

Thank you!


Cloudy Acrylic Varnish

Question asked 2021-04-28 08:22:43 ... Most recent comment 2021-04-29 11:34:45
Varnishes Acrylic

​I am a relatively new artist and made a rookie mistake. .

I am used gloss varnish on my acrylic paintings for the first time.  I applied two coats of Liquitex Professional Gloss Medium and Varnish and it has made it a mess.  

I suspect I did not let it dry long enough and then overworked it (rookie mistakes). It may also be that I put it on too thickly. 

Unless it is in absolutely perfect light, it has a very glared and smudged appearance.  

Any suggestions of what I can do to fix it? I am very proud of this painting; it took a long time and is a paid commission.  I am desperate to save it.

walnut alkyd and inter layer adhesion

Question asked 2021-04-26 12:39:20 ... Most recent comment 2021-04-27 13:14:25

​Should a shiny, lower paint layer need to be roughened to give it tooth before painting over it (mechanical bond), or would the chemical bond between the two layers be sufficient?

I've been adding walnut alkyd directly to my paint blobs on the palette before painting, without OMS (which is easy to overuse), and enjoy the viscosity, but the result is sometimes a shiny layer .

Thank you,


Bohus Bial 168, anyone?

Question asked 2021-04-14 09:27:56 ... Most recent comment 2021-04-22 07:57:02
Health and Safety Environment Drying Oils Paint Mediums Paint Additives Solvents and Thinners


I wonder, is there anyone here that knows Bohus Bial 168? it is supposed to be a harmless white spirit alternative. Bio degradeble, non toxic, non volatile, better working than white spirit, all natural, etc. and supposedly you could even use it as a painting medium.

To me it sounds as too good to be true, but who knows... Would be great if it realy works...

Fat over lean in article on Natural pigments

Question asked 2021-04-21 09:16:19 ... Most recent comment 2021-04-21 19:13:58
Drying Oils Oil Paint Pigments

There is an article at by George O'Hanlon called „Painting for Posterity with Modern Oil Paints", about some aspects of oil painting. I'm posting a question about it here, because „Forum" section at hasn't been functioning for some time (or it seems that way - not possible to start a new topic) and also because George sometimes posts also here. I'd like to know his opinion – but of course everyone is welcomed to share their knowledge and experience.

Quoting from the article:

Fat-Over-Lean Rule

You are probably familiar with the fat-over-lean rule. What the fat-over-lean rule implies is flexible over less flexible paint layers. When you apply a more flexible layer on top of another, the final paint film will be more resilient and more resistant to cracking. Increasing flexibility is accomplished by adding more medium or oil, or lowering the pigment volume concentration of the paint with each succeeding paint layer.


However, this is typically difficult to achieve in practice. Most artists don't understand what constitutes fat or what is lean. It is impractical to measure the ratio of pigment and binder while painting. What I will tell you next may sound like heresy but you do not need the follow this rule if you use paint at its CPVC, which is applying paint straight from the tube, and paint thinly. On the other hand, working in thick paint layers and/or with lots of medium or oil added to paint requires one to observe the fat-over-lean rule.


I visit mitra forums from time to time and there already has been discussion about fat over lean, and so far, the conclusion was, that in fact every paint is formulated to be lean out of tube (i.e. made with just neccesary amount of oil, at CPVC or so).

The statement of my interest is : „(…) you do not need the follow this rule if you use paint at its CPVC, which is applying paint straight from the tube, and paint thinly." It is not clear, George was reffering to Rublev colors or any oil paint in general. And that makes me wonder; whether he meant paints based on various pigments in same oil, or in various oils as well.


You see, there are manufacturers like Williamsburg, Gamblin, Michael Harding and of course Natural pigments, who use linseed oil as a default binder for their entire line of oil paints and they also offer some pigments ground also in other oils like walnut or safflower. If one wants to use only linseed oil based paints, it is possible with these brands. But on the other hand there are many manufacturers who use different oils or oil blends for different types of pigments. One example I can mention is Blockx; they use linseed oil for iron oxides, natural earths, blacks and few other pigments (e.g. PY53, PY154, PY184) or blends (e.g. Paynes Gray, Indigo) and poppy oil for everything else, i.e. blues (organic and inorganic pigments), cadmiums, cobalts, organic reds, oranges and of course whites.


Now, let's say one wants to use Blockx oil paints to create grisaille underpainting using chromatic black (e.g. burnt umber and ultramarine) and flake (lead) white and then lay a glaze over it with transparent mars yellow and the painting will be done according to what George wrote, i.e. applying paint straight from the tube, and paint thinly.

Ultramarine and Flake white are in poppy oil, burnt umber is in linseed oil. Seems to me, that burnt umber is stronger than ultramarine, so more ultramarine will be necessary. Then, as grisaille needs to be bit lighter than a final painting would be in grayscale, relatively large proportion of white will be necessary; of course it can vary depending on particular part of painting, but my point is – this will result in paint layer consisting mostly from poppy oil as a binder. Let's say it'll be left to dry and cure for two weeks, and then the glaze based on Transparent mars yellow will follow; in case of this color, linseed oil i sused as a binder.

Therefore, it will be a paint layer with pure linseed oil as a binder over a paint layer with mostly poppy oil as a binder; is this alright? According to what I know and read so far, I'd say - not really... as oils like poppy and safflower should not be used in lower layers, because they form weaker layer. And yet, so far I haven't read any article or blog post about paint layers cracking in such situations.


I wonder, if it is really a problem, when one uses „weaker" oil like poppy underneath „stronger" oil like linseed. Whether it is only about oil, or also about pigment; lead white is known to make strong and flexible paint layer; is it possible that lead white in poppy oil will still dry into paint layer as strong as some other pigments in linseed oil?


What do you think about it?

alkyds: I'm not finding actual literature on chemistry of oil primers

Question asked 2021-04-19 09:30:20 ... Most recent comment 2021-04-19 23:19:36
Grounds / Priming Drying Oils Animal Glue Oil Paint Rigid Supports

​What the title says.

I was interested in using commercial grade alkyd oil primers to prime my own canvases, 

the only thing I could find were generic warnings from artists who were not chemists to "use only art grade materials!!"

...and that's fine if that's the answer! :)  it's more the principle than the $.  if utrecht oil primer @$60/gal >> zinsser oil-based primer @$15, I just like to know specifically what makes it so.

I just need to know WHY.  because some times, there IS no difference.  a $15, 50# bag of whiting powder from the clay supply store is the same as a $15, 4# bag of "ground marble" from an overpriced paint brand.  and some times, there really is a seriousdifference after all, and, I want to educate myself.

but just using google I'm finding very little.  and paint brands like to keep their formulas proprietary, as well.

what's the difference between a urethane alkyd and a silicone alkyd?
...and "alkali-refined linseed oil"?

are all three alkyd categories cross-compatible (will stick to each other)?
 is there a chemical relationship between a urethane alkyd and a polyurethane varnish?

alkyds are 100% compatible with traditional oil paints, or no?

enamel gets used like a marketing term all over the place for all kinds of totally different products... does it have a specific technical meaning?

"titanium white oil paint" versus "oil primer" vs an oil-based gesso (I guess acrylic gesso is more common)
 is the difference between paint, primer, and gesso, the amount of whiting powder and pigment filler versus the amount of binder?  primers have more filler to be thicker and more opaque, is it just that simple or there's more to it?

I'm sorry there's so many questions.  these are things I've wondered for YEARS and never found clear answers to. 

I even have the artists' pigments books which are fascinating.  i loved making the pigment connections when I got into both car autobody+paint and pottery glazes.
the fellow at NAPA auto paint was explaining that toyota's gold paint from 2000 bleaches in hawaii's equatorial sun to a silver-- it has quinacridone red, which is a mostly permanent organic pigment but apparently 20 yrs of direct UV exposure, will break it down).

But I never really learned about binders!

I figure the conservationist folk here would know better than anyone!    

I'm a smart dude and I'd be happy to read through some literature if you can point me in the right direction, to something that's just laymen enough for me to understand it while also technical enough to correctly describe the chemistries of these different alkyd binders

 (I have some collegechemistry background, doesn't have to be totally dumbed down; but perhaps not so technical that I need a masters in petroleum engineering and matsci!).

thank you again for the help,


"Slightly" underbound question

Question asked 2021-04-10 16:28:12 ... Most recent comment 2021-04-19 21:24:49
Oil Paint Drying Oils Art Conservation Topics Grounds / Priming

​Hello everyone- I am so happy to have found this resource and want to preemptively thank you for providing this information to people. 

I work in oils but haven't had any traditional training (in undergrad I did graphic design) and everything I have learned was just through self trial and error and gleaning info from friends. 

Recently I had an issue with the lightfastness of a color and through that experience learned about lightfastness which is easy enough to fix (I replaced tubes of paint) ---but it set off my anxiety brain. I wondered what else I may not know about (and the issue with learning by trial and error is what if the issue doesn't show up for years!? I used that color with horrible lightfastness for two years in a few paintings because the issue didn't show up until now.) 

So I have embarked on a journey of asking very technically-minded painters their opinions on every part of my practice and by researching on sites like this one. 

My painting process is luckily very simple which I hope will save me from huge structural issues. I actually have always just painted from the tube and have added no solvents or mediums. Much of the time a section of a painting will be done wet on wet in one layer but other times I will rework a section after it has dried. Since it's just the oil paint my understanding is I am painting only with fats and that should be structurally sound. The only times I've ever had cracking was when I really violated a thick over thin rule (like painting a relatively thin layer over a thicker color that was still tacky). In those cases the cracks showed up by the next day.

However- talking with people and stress-testing old canvases I have learned that I am not gessoing enough and that the acrylic gesso I was using is not the best quality it could be. I'm going to in the future move to using Golden's acrylic gesso and will do at least three to four layers. 

I have found that my paintings often are underbound. A finger rubbing won't do anything but if you rub them with some pressure with a paper towel the towel will be very slightly stained. 

I think going forward the better gesso (and maybe even trying oil gesso) as well as adding a tiny bit more linseed oil to my paints will help fix this issue. But I am curious about the paintings I have from the past decade of painting. This isn't an issue that has come up as the paintings aren't rubbed or placed under stress-test situations in the real world. I've sold many paintings over the years so I do have a concern about their archival-ness. 

Very long-winded but I suppose the question I am most curious about is whether there is a spectrum of unbounded-ness? If something is "slightly" unbound and kept in normal safe conditions will it be safe for at least our lifespan? (Obviously this is probably a case-by-case answer but any knowledge shared would be very appreciated)

Thank you so much for your time and insight. 


PS also am curious about fingernail tests. I've read that a way to make sure a layer is dry enough to paint over is to scratch it with your nail and if it comes off powdery and not gunky it's ready. But other people asking questions on here about the structural integrity of their work have said that their pieces aren't effected by a fingernail test as a way of proving they are sound. I may be going too intensely with my stress-tests but yes if I'm sitting there scratching with pressure over and over on a spot I can start to damage the paint. 

rigid supports, mdf vs plywood?

Question asked 2021-04-19 08:56:09 ... Most recent comment 2021-04-19 12:51:11
Grounds / Priming Drying Oils Animal Glue Oil Paint Rigid Supports

​Good morning!

I'm just getting back into oil painting and silverpoint after a 10-yr hiatus.  I got back into sculpture last year.
I'm DEFINITELY over thinking things, but that's just who I am.  I'm a very indecisive person and like to know everything about a problem! 

practically speaking, my first efforts are NOT going to need to be archival haha.  But I still want to make the right decision.

Anyway: to begin,
I have TWO use cases.

one, I'll be securing hemp canvas to a rigid backing and then using an oil primer,

two, I'll be securing the same canvas to a rigid backing and then using traditional gesso [whiting].

three... I could just prime or gesso the panel directly...

so, which is better as a rigid support for small-medium panels, say up to 8x20", probably 1/4" thick--

I see it this way:
I want to use plywood because,
more humidity resistant (mdf puffs up if it gets wet)

advantages of mdf:
dimensional stability, it is smooth and dead flat, plywood warps

I'll be making a trip to home depot in the next day or two so looking forward to your advice!  ....mdf or plywood?

I DO have three other thoughts:

there's a dude on facebook marketplaceselling 1/8" aluminum for super cheap, $70 for 3x8' (compared to $25 for 4x8' cheap plywood, so more expensive but not MUCH more per panel)..  totally archival, light weight, dimensionally stable and moisture-proof... can get bent though haha.  And harder to cut up (would need to borrow a table saw and buy a metal cutting blade, not a huge deal).  can paint DIRECTLY on aluminum too, like copper panel but much cheaper.  worth exploring?

what ever happened to painting on fiberglass canvas, which doesn't rot?  I'm having a harder time finding it for sale, but 10 years ago you could get it.  were there issues with the primer adhesion?

lastly, least if people are using a canvas mounted to a rigid support like I am... why doesn't anyone use acrylic sheet?  plastic is easy to cut, super stable and waterproof, cheaper than aluminum although pricier than plywood, and you don't need oil to stick directly to the acrylic plastic sheet if you're going to tack down your canvas first, then prime that.  

Protecting wood from moisture

Question asked 2021-04-05 16:28:27 ... Most recent comment 2021-04-05 17:56:41
Oil Paint Rigid Supports Sizes and Adhesives Industrial and Non-Traditional Products

Hi All,

Thanks to the Painting Best Practices course, I finally decided to ditch flexible canvas supports in favour of mounting linen to wooden panels. Never knew the former could be so terribly problematic! However, with this change some new considerations sprung up which need clarification. So far the preparation looks like this:

For studies I plan to use some sort of solid wood support (or maybe HDF?; but certainly not plywood because it checks) impregnated on all sides with one or two applications of 10% solution of Paraloid B72 in ethyl acetate. Then I would put some Lead Ground/Acrylic Dispersion Ground.

For final pieces I will apply the Paraloid B72 as stated above and will then use pH neutral PVA adhesive to glue the linen to a birch plywood. The linen would be pre-primed with 2x GAC 200 and some Lead Ground.

The questions are:

1) Is the aluminum foil and low-density polyethylene combination a good alternative to Paraloid B72? Should the aforementioned procedure (ironing the aluminum foil onto the panel) commence on a bare wood surface or a prepared one (Paraloid B72)? Are there concerns over this practice?

For me, the thin aluminum sheet seems to be overly susceptible to tearing, abrasion and so on. However, it can't be denied that it's the best moisture barrier. I know for a fact that there are similar alternatives such as Marvelseal 360 and alkyd-based aluminum paints. These are expensive, though. What are your take on this as a whole?

2) Does the Paraloid B72 solution have a limited shelf-life like shellac? I don't know if the one available to me has HALS/UVLS additives or not, but this is something to consider as the minimum amount sold is 1 litre. Also, can I apply Acrylic Dispersion Ground over this resinous sizing? Will the underlying varnish complicating matters as it remains redissolvable?

As a note to my last question, the potential problem I see with this practice is that solvents can penetrate into the underlayers and cause trouble when varnishing and cleaning. In any case, I decided to use solvent-based sizes over waterborne ones specifically to avoid fiber rising and warping.

3) When using solvents, can the Regalrez 1094 that has sunken in trigger the redissolution of the dried linseed oil paint or the leeching of unpolymerized free fatty acids?

This question is just me toying with an idea. I've learnt that some low molecular weight varnishes tend to sink in somewhat and that solvents, as they evaporate, can bring unbound substances to surface. My reasoning behind this notion is that the industry uses polymeric - high molecular weight - varnishes for acrylic paints because the surface is more porous than that of oil paints'. Ergo, the sinking in of varnishes is something that was found problematic, wasn't it? I'm especially interested in your stance on this one. By the way, feel free to correct me if I'm wrong somewhere.

4) Can anti-fungal agents or anti-insect products be applied in any shape or form?

Sorry if I ask too much!

Thanks in advance,

Péter Hegedűs

Recipies for making oil paint in tubes

Question asked 2021-04-03 10:57:54 ... Most recent comment 2021-04-05 16:51:03
Drying Oils Oil Paint Paint Additives Paint Making Pigments Scientific Analysis

Dear MITRA experts, I would like to ask for your advice. I want to make my own oil paint in tubes, in small batches. My neighbours have a viscous paste mixer and a tiny three roller mill for ointments. I have found formulations for many pigments, can you tell me if these will make a good paint and if it can be improved in terms of modern science and your experience? A couple of examples:

  • For Ceruleum, to obtain 100 grams of paint: Pigment blue 35: 84 grams, aluminium stearate 1.3 grams, binder 16.7 grams. For 100 grams of binder: polymerised alkali-refined linseed oil 47.8 grams, bleached poppy seed oil 47.8 grams, beeswax 1.91 grams, mastic resin 2.87 grams.
  • For Cobalt Violet Light, to obtain 100 grams of paint: Pigment Violet 49: 70.7 grams, aluminium stearate 2.4 grams, binder 29.7 grams. To obtain 100 grams of binder: Polymerised alkali-refined linseed oil 49.25 grams, bleached poppy seed oil 49.25 grams, beeswax 1.98 grams.

There is a small amount of manufacturing losses included in all recipes. The mastic and beeswax are said to be dissolved in heated oil. Would it be possible for professional artists to use this paint? How can I improve it?

Maintaining an oil painting

Question asked 2021-03-31 17:14:22 ... Most recent comment 2021-04-05 11:35:26
Oil Paint


I have a couple of questions about how to maintain an oil painting. 

I read on this forum that a painting can be dusted a few times a year with a soft brush. Is there a particular type of brush that you would recommend for this?

Also, for an unvarnished oil painting, can you explain how grime becomes chemically bonded with the paint? I wasn’t able to find any information about how this process happens. Also, once the grime is bonded can it be removed?

Thank you for your help

Zinc grounds in linen updates

Question asked 2021-03-31 17:16:12 ... Most recent comment 2021-04-01 18:09:26
Oil Paint Flexible Supports Grounds / Priming


I have been reading some of the questions on this forum from a few years ago about the concerns with zinc in oil grounds on linen. I was wondering if there were any updates or studies on how such linen may behave over time? 

I am trying to figure out what might happen to the paintings I have already completed in linen with these grounds. 

Thank you for your help

Tinted Grounds for Silverpoint

Question asked 2021-03-14 09:02:58 ... Most recent comment 2021-03-18 21:32:54
Acrylic Chalk Drawing Materials Grounds / Priming


I am currently involved in running a series of tests for an upcoming project. I want to create a series of silverpoint drawings on some uniformly tinted 5" x 8" HDF panels. For the dark values in silverpoint I want to achieve a mid to three quarter tone gray (but no more), which I imagine touching up with some white highlights as a final touch. 

So I'm trying to decide what is the best way to prepare the ground, do I go traditional (chalk gesso) or modern (acrylic)? 

For to the acrylic direction, I have already created two tests: 

One is a smooth yet absorbent HDF surface prepared with Golden Acrylic Gesso (which I have tinted using acrylic tube paint). 4-6 coats. Lightly sanded inbetween to remove brushstrokes. The tint is good. Over this I brushed a layer of (transparent) Golden Pastel Ground. The result is very toothy and feels like rough sandpaper. Nice. The silverpoint test marks I have made appear to be darker than usual. Thus there appears to be sufficient contrast between the silverpoint and the tinted ground. I imagine touching up the highlights using a white gouache, but havent't tried it yet. Will there be any absorbency issues with that? Should I use acrylic paint or is gouache OK?

The second test is on a smooth yet absorbent HDF surface prepared with Golden Acrylic gesso over which I brushed Golden Silverpoint Ground. This time the acrylic gesso was untinted because I knew I would be introducing the tint through the Golden Silverpoint Ground - which is opaque. The result feels less toothy to the touch, (actually it feels like smooth plastic), but does appear to take the silverpoint test marks well enough. Made repeatedly thgese could become the mid-value gray tonality I seek? I haven't tried the white gouache highlight test here either but my questions are the same. Will there be any absorbency issues with that? Should I use acrylic paint or is gouache OK?

However, my main question concerns the traditional approach. If I were to go that direction using RSglue/chalk gesso, I imagine adding some terra verte and maybe a small bit of burnt umber to my gesso ground prep. This would achieve the tint I am looking for. And if these dry pigments were less than 10% by volume (surely it would be even less than that) I think that these should be no problem to the integrity of the gesso. Is that correct?

In addition, I am wondering if there is a way increase the tooth of the traditional chalk gesso ground so as to increase the value of the silverpoint marks? Marble dust or other additives, etc...? Coarse sanding of the final surface? Any suggestions? 

Thanks for the feedback. I really appreciate being able to ask my questions of well informed resources.

Combining Acrylic over graphite

Question asked 2021-02-11 10:35:28 ... Most recent comment 2021-03-16 17:54:32
Acrylic Drawing Materials Paint Additives Paint Mediums Pencil Varnishes

​Hello dear people from Mitra!

I have a question regarding mixed media basically. 

If i have a fully rendered graphite pencil drawing on thick watercolor paper (with all details and deep shadows done, it has a lot of graphite on it) and i want to paint over that with acrylics , what is the best and safe way to do that? 

Is it enough to just put a layer of a clear Matte Medium and than to paint over that with acrylics? 

Or is it safer to first put a coat of Pastel, Charcoal Fixative ( it is Talens Fixative and it contains :  Colourless resins, ethanol ) and i think it is workable fixative,   and then to paint with acrylics and to use a acrylic matte medium in it? 

Thank you in advance and i hope you are all ok and safe during these times.

Kindest regards

Marko Karadjinovic


Question asked 2021-03-15 16:40:13 ... Most recent comment 2021-03-16 11:42:15
Art Conservation Topics

​I am applying diluted Jade 403 to acrylic paint to the the cracked/damaged areas before retouching. Can anyone recommend how diluted the pva(Jade) should be and if it is a good idea to apply more than one coat. 

Mysterious Discoloration

Question asked 2021-03-12 10:21:44 ... Most recent comment 2021-03-15 15:06:14
Oil Paint

​Hi Brian, thank you for your response. Very astute of you to ask about storage. My panels were stored for several months in vellum envelopes in the mostly dark storage racks of my studio. I always thought only lead based materials would yellow. So I was surprised when I saw the extent of yellowing on these paintings. 

I used a fair amount of medium on the Titanium white paint for the backgrounds. The paint I use is this luscious, rich, Italian paint, but quite stiff out of the tube. 

Why RSG? I smile as I write this- I'm old school! I was trained in the 80's and 90's art schools, and that's what we were taught. I haven't had problems before, but of course, I am open to updating my methods. 

Thanks! Maryam

Mysterious Discoloration

Question asked 2021-03-11 21:28:29 ... Most recent comment 2021-03-14 21:35:21
Oil Paint

​Hello MITRA forum, I just experienced an oil painting disaster. A series of oil paintings with Titanium white backgrounds yellowed and dulled after several months in my studio storage. Where did I go wrong?! Was it my ground? Oil paint pigment? Medium? Varnish? All of the above?! These are the materials I used: 

1. RSG sizing on portrait linen over maple board.

2. Acrylic gesso ground (100% acrylic polymer).

3. Titanium white oil paint for the subject backgrounds. Paint tube notes Titanium Dioxide in safflower and poppy oil.

4. Neo Meglip medium. Described as a contemporary version of Maroger. Contains Petroleum Naphta.

5. Satin archival varnish. A mineral spirit acrylic aerosol w/UVLS. The fine print notes contains: Acetone, Propane, N-butane, Petroleum Distillates, Solvent Naphta, Trimethylbenzene.

Thank you for your thoughts!


Golden Polymer Varnish for Egg Tempera

Question asked 2021-03-05 21:47:38 ... Most recent comment 2021-03-12 08:09:01
Egg Tempera Varnishes

​I'm looking into using Golden Polymer Varnish on my egg tempera icons. What would be the drawbacks of using this varnish?

In my experience, other varnishes cause FAM or blooming (I think the solvents in oil-based varnishes aggravate the lipids, especially Gamvar). Golden Polymer Varnish is the only water-thinnable varnish I've found that is also reversible/removable (Lascaux doesn't seem to be reversible, at least that I can find...or is it?). Golden does not seem to cause immediate blooming in my tests, even on new paint swatches a few days old (not that I plan to varnish that soon). Reversability is important to me since it is quite likely for an icon to get lipstick on it eventually, if not oily spot, etc.

I like the look of the matte surface as it is quite similar to the egg; the gloss looks fantastic over the gold. A Golden technical expert said to use the gloss first to seal it, then use the matte over top for the final sheen. So, I can cover the entire icon (gold and tempera) with gloss, then cover only the tempera with matte. The entire surface is then protected and removable.

I've also seen in another thread the recommendation to use Krylon Crystal Clear as an isolation coat. I'm a little worried about orange peel, to be honest, but I think that's worth looking into as well.

Also in another thread was the concern about the alkalinity of this varnish. Would that negatively interact with the egg tempera? The expert at Golden said they do not recommend the Polymer Varnish for oil paint. The binder in tempera is a drying oil. Will this be problematic?

Thank you for your help.

Brian Matthew Whirledge


Linen canvas and GAC 200 question

Question asked 2021-03-07 05:51:14 ... Most recent comment 2021-03-11 04:48:52
Grounds / Priming Flexible Supports Oil Paint Sizes and Adhesives


Some new questions sprung up thanks to covid and Brexit (I get my stuff from GBR to EU). A 450 GBP packet now costs 140 GBP just to deliver to Hungary. Before Brexit, large shipments such as this were gratis or cheap at minimum... I am not here to rant, just wanted to take stock of the unfortunate situation.

Do you happen to know good and trustworthy canvas brands and retailers, preferably in the EU? Artfix is pretty widespread here, but markedly costlier than the others. I would like an artist's grade linen canvas that is also not prohibitively expensive.

Secondly, is it worth to save money (even 140 USD!) by buying a medium textured canvas instead of a fine one? Or is it less archival for being more porous/more loosely woven? I will do portrait stuff, by the way.

With regards to sizing, I'm planning on getting the GAC 200, which is proposed by Sarah Sands (2 very thin layers) and the tech support guy I talked to. However, on Golden's webpage it says it's not recommended for flexible supports.* I firmly trust the people from Golden (more than the webpage), just wanted to double check if someone can reassure me that it is adequate. :) *Note: I will further apply 2 coats of Golden acrylic gesso and 1 layer of Rublev lead ground, so the GAC 200 will not be used alone, if that matters.

By the way, are unused credit cards ok for the thin application of sizes/grounds?

Thanks in advance!

Hope you're all well,

Péter Hegedűs

Acrylic dispersion ground adhesion problems with acm panel

Question asked 2021-03-07 06:08:25 ... Most recent comment 2021-03-09 02:34:43
Acrylic Grounds / Priming Oil Paint


I'm an oil painter that has had good experiences with using ACM panels with an acrylic dispersion ground as a substrate to paint on. However I noticed some adhesion issues with the last batch of panels I primed and was wondering if anyone has any advice on how to move forward, things to consider etc..

My process for preparing the ground has been as follows;

1) Lighlty scuff/sand the polyester surface of the ACM panel making sure not to sand down to the aluminium surface.

2) Clean the surface with 97% Ethanol

3) Apply a first layer of Golden Acrylic 'gesso' mixed with GAC 200 in a ratio of roughly 60/40 - 70/30

4) Leave to dry for 24 hours

5) Apply a second coat of the Acrylic 'gesso' with a little bit of water added to improve consistency for easier brushing on the primer. (Max 10% of water) I don't measure those amounts precisely, doing just by feel.

6) leave to dry for 24 hours

7) Repeat steps 5) and 6) 2 times.

8) Finish the ground with a layer of pure Golden acrylic gesso, no water added.

I live in Belgium and prepared these panels last month when it was pretty cold (wintertime) although the temperatures in my studio were normal room temperature during the day. During the nights it will have beeen colder however, so some temp fluctuation will have occurred. I left the panels to dry for 2 weeks and performed an adhesion test on one of the panels by crosshatching with a blade making little 1/10 inch squares and applying a piece of ducktape and swiftly ripping it off. Result: over 50% of the primer stuck to the tape and came loose...

If I take a palette knife and scratch the side over the delaminated area trying to remove more paint I have to apply some pressure to scratch it off, so there is some amount of bonding but I'm not happy with that result. 

How to move forward? Will all of these recently prepared panels be totally unsuitable to paint on? Do I have to worry about more severe delamination of the painted surface in the future? What risks do I take when painting on this surface? Are there ways to improve the current state of the grounds without completely sanding off all of the layers and starting over? 

Any advise highly welcomed and appreciated. 

Kind regards,


restoring wood and canvas sculpture painted with acrylic

Question asked 2021-03-04 17:55:48 ... Most recent comment 2021-03-04 18:36:45
Art Conservation Topics

​I am wondering if there is any concern/issue of compatability using fluid acrylics over older acrylic paint.  There is a lot of cracking both on the painted wood and painted canvas. Also, if anyone has any suggestions about matching colors, I am open to that- but less critical (I'm not a trained painter! Or restorer for that matter.)

Painting with gouache on panels

Question asked 2021-02-27 13:00:10 ... Most recent comment 2021-03-02 12:34:57
Gouache Grounds / Priming Pigments Rigid Supports

I would love to hear any thoughts from a conservation standpoint regarding using gouache on prepared rigid surfaces. I paint with gouache (I typically use Holbein or Turner acryla gouache for their flatness and opacity, but have experimented with different brands) on gessoed cradled panels, either baltic birch or hardboard. Since gouache is water-soluable (though I find that the acrylic gouache is less inclined than artist's gouache to reactivate with moisture), I'm curious about whether it would be advisable to add some kind of finish to the board after the painting is done. I've experimented with a few different varnishes, but I know these kinds of finishes can be problematic, and I also don't like how the varnish changes the surface of the painting... even matte ones add some kind of sheen. Is there a way to add a level of protection from light and moisture to gouache works on panel without framing/glazing them? Thanks for any opinions.

Stand oil gone hazy/foggy

Question asked 2021-02-25 15:34:37 ... Most recent comment 2021-03-02 06:02:00
Oil Paint Drying Oils Storage



In the picture above, hopefully you will se the haziness I am talking about. I don't know if this is ok? It developed little spots of "opaque smudges" everywhere. The stand oil was not exposed to direct sunlight. 

Another similar question is that W&N satin metacrylate-based varnish is expected to settle down, right? With this one I am not so much concerned because it has to be shaken well before use anyway. 

Thanks for your input! 

Péter Hegedűs

Oil Paint Thickeners

Question asked 2021-02-28 16:26:37 ... Most recent comment 2021-02-28 20:16:05
Oil Paint

​With some pigments my oil paint slumps.   I use Tixogel VZ, Aluminum Stearate, wax, and fumed silca.  I use a ball mill with acetone and linseed oil to grind the pigment and then evaporate the acetone.  I find with a pigment like ultramarine blue I still have problems.  The oil also separates from the paint in the tube.  I just don't know how much of anything to use or how to use it.  I grind the Tixogel VZ into acetone first, that is about all I can find on how to thicken.  Thanks for any input.  

DTM Bonding Primer by Sherwin Williams - presence of zinc

Question asked 2021-02-24 01:07:40 ... Most recent comment 2021-02-26 17:45:54
Art Conservation Topics Grounds / Priming Scientific Analysis

In a number of places you recommend DTM Bonding Primer by Sherwin Williams as a ground, particularly for use with aluminium panels. 

The EDS data sheet suggests it contains zinc.

Zinc (as Zn)             2% by weight

Zinc Compound      3% by weight.

In dry form the percentage of zinc will be much higher. 

Yet elsewhere you frequently warn to check for zinc content. For example in your Grounds and Primers technical resources state: '​Zinc white has been found to react with components in oils and alkyds and form “metal soaps,” which in turn can give rise to delamination, wrinkling, the formation of white-colored aggregates, and the softening of ground/paint layers. Research is presently being carried out to determine the extent of damage that can occur when these materials are present.'

Can you please clarify? Is the zinc in a different form or are there other reasons why this product is suitable despite the presence of zinc? Have I misread the EDS - I'm not a chemist! There are a number of people on my forum (Wetcanvas) discussing this and we are interested in the clarification. 

Zinc white detection

Question asked 2021-02-22 07:48:52 ... Most recent comment 2021-02-25 16:51:01
Oil Paint Pigments


It has already been written quite a lot about problematic nature of Zinc white in oil. In case one is not sure about partcular oil color composition (e.g. no pigment info on a tube, or no longer existing company, or just customer service not answering to questions), is there any way how to detect the presence of zinc white? 

Kremer pigmente offers various chemicals

Is it possible to use some sort of chemical (liquid, powdered) which, when mixed with paint, will react with zinc white in a certain way (for example the hue of paint will change) and therefore prove its presence even if it is present in small amount?

DTM Bonding Primer by Sherwin Williams - presence of zinc

Question asked 2021-02-23 21:41:29 ... Most recent comment 2021-02-23 21:32:00
Art Conservation Topics Grounds / Priming

In your reference materials on Grounds and Primers you are very clear about the need to avoid zinc: "zinc white has been found to react with components in oils and alkyds and form “metal soaps,” which in turn can give rise to delamination, wrinkling, the formation of white-colored aggregates, and the softening of ground/paint layers." 

On several places on this site you recommend DTM Bonding Primer by Sherwin Williams, particularly for ACM. 

The EDS data sheet suggests it contains zinc:

Zinc (as Zn)             2% by weight

Zinc Compound      3% by weight.

I'm not a chemist but a group of us at Wetcanvas forum are seeking clarification. Is this zinc in a different form that doesn't create problems? If so what forms of zinc do not need to be avoided? Have I misinterpreted the EDS?

Preparation for hardboard - understanding the questions

Question asked 2021-02-22 03:17:10 ... Most recent comment 2021-02-22 20:53:29
Art Conservation Topics Alkyd Grounds / Priming Rigid Supports Scientific Analysis

I usually paint on hardboard/masonite. I want to strengthen my conservation preparation which includes: a) Best techniques /materials; b) Understanding the questions and answers. 

I have been recommended Zinsser Cover Stain (VT Styrenated Modified Alkyd, Calcium Carbonate, Magnesium Silicate, Titanium Dioxide.) It would be really simple if it worked. But I'd definitely take proven methods over ease of use and possibilities. 

I’m trying to understand the questions. 

(1. The painting surface: (canvas, board, plaster wall) needs to be resistant to movement (expansion/contraction or bending), moisture, degradation (breaking down of the material) or release of chemicals. For masonite I build a cradle to keep it firm. Sometimes they need sealing. Chemical stability is a plus.

2. Barrier (size/etc): Some surfaces need sealing to minimise moisture absorption, moulds, etc and to stop it leaching chemicals into the painting. This barrier is best if it’s chemically stable including pH neutral. 

3. Ground: Oil paints need ‘tooth’ to grip a surface for a) Easier laying of paint; b) Sufficient adhesion to avoid peeling down the track. Best grounds will be very stable so that they don’t leach chemicals or react with the oil or the pigments, and stable so they don’t break down. All the ingredients. It also shouldn’t be too absorbent of either pigment or oil.


I’m trying to understand the questions:

1. The painting surface: (canvas, board, plaster wall) needs to be resistant to movement (expansion/contraction or bending), moisture, degradation (breaking down of the material) or release of chemicals. For masonite I build a cradle to keep it firm. Sometimes they need sealing. Chemical stability is a plus.

2. Barrier (size/etc): Some surfaces need sealing to minimise moisture absorption, moulds, etc and to stop it leaching chemicals into the painting. This barrier is best if it’s chemically stable, including pH neutral. 

3. Ground: Oil paints need ‘tooth’ to grip a surface for a) Easier laying of paint; b) Sufficient adhesion to avoid peeling down the track. Best grounds will be very stable so that they don’t leach chemicals or react with the oil or the pigments, and stable so they don’t break down at molecular level, crack, movement etc. All the ingredients. It also shouldn’t be too absorbent of either pigment or oil. 

Questions: 1. What is the best proven preparation for board for conservation? 2. Where can I find the research-based material to build a basic understanding of the correct questions/criteria? Is my list close? 3.  Zinsser cover stain - I gather there are variations in VT Styrenated Modified Alkyds - is there a view on this product or similar? In some ways I'm interested in asking their technical team the right questions. The test of time it hasn't passed, I know. 

venetians schools 6-9 coats of size/primer for linen canvas

Question asked 2021-02-20 19:32:59 ... Most recent comment 2021-02-22 11:44:26
Animal Glue Grounds / Priming Flexible Supports Sizes and Adhesives

​Hello Mitra,

I read a while back that since the venetian school was painting on linen, and not wood, that they had to put less coats of size and gesso on their canvases.  Something along the lines of 6-9 coats.   These size coats and gesso coats (gesso sutile) were done thinly too.  This was done so that the size and gesso wouldnt crack due to the flexibility of the canvas.  I also read that this was also one of the reasons they went thicker with their paint.  The thicker paint served as an extra protection from the atmosphere.

Are 6-9 coats on linen fine?

Best Regards,


sun thickened and studio thickened linseed oil for mediums

Question asked 2021-02-20 07:59:11 ... Most recent comment 2021-02-20 10:11:20
Paint Mediums

​I refined my own linseed oil (from flaxseed oil). It was my understanding that you could 1. put it in a jar in a studio window and age it; 2. put it in a tray in direct sunlight for a period of time then put it in a jar. These have now become very viscous. I thought this was good; that it had become "stand oil". But reading the Mayer book, I think he says this oil is oxidized and cannot be used due to high likelihood of more yellowing. I believe the people at Natural Pigments said thickened oil has to be heated, not just aged. So my question is: is this 'studio/outdoor thickened' oil useless? I would have to mix it with thinner oil or solvent to use it.

Correcting an overly dark undercolour in Imprimatura

Question asked 2021-02-18 02:26:56 ... Most recent comment 2021-02-19 21:21:45
Oil Paint

​Dear MITRA staff I  was informed by my teacher about a process he referred to as "double Improimatura" in which one starts with a coat of Venetian Red oil paint or similar (thinly applied) followed by a light grey layer, which should be scumbled over the top. This was supposed to create an opalescent kind of grey. However despite using very thin layers, I've found the Venetian Red is quite dominant and I'm concerned about it showing through more and more over the years as I know oil paints become increasingly transparent over time. Needless to say, perhaps, I probably will not use this procedure again!--or if I do it will be with a much, much lighter and more translucnet undercolour than Venetian Red. In the meantime though I would like to salvage the panels I've treated in this way, to whatever extent is possible. Multiple, very thin, scumbled/scrubbed on coats of Lead White mixed with a light grey (composed of palette scrapings neutralised to a grey colour) haven't subdued the VR to the extent I would prefer so I thought I should do some more scumbled "layers" with some titanium thrown into my grey mix, given that it has more opacity than Lead White. I dont want to compltely obliterate the VR, just for it to be welll subdued so that my grey remains fairly grey not a grey-sprinkled dull pinky colour. BTW I am prepared for the fact that all these panels may need to be considered suitiable only for studies or master copies, given that the prognosis in terms of overall darkening may be rather dire. Would this be an appropriate level of pessimism to have? Is my plan--to continue with a couple more scumbles, this time with some Titanium White added as noted above-- if executed with due regard to fat over lean (flexible over inflexible) principles and if pplied in the same very thin, scrubby scumbly way, reasonable? 

A quest for long-lasting stretched linen surface

Question asked 2021-02-14 19:21:52 ... Most recent comment 2021-02-17 07:24:19
Oil Paint Sizes and Adhesives Grounds / Priming Flexible Supports

​Hi all,

I would like to create the most archival stretched linen surface for oil painting, as far as my budget allows it.

First of all, I plan to use lead ground in the last one or two layers in the process. However, I was thinking about including acrylic grounds, so that I don't use up the expensive lead ground that fast. However, there seems to be a division in the art world, where some swear by the use of sizing before lead grounds, whereas others just apply four coats of acrylic gesso. Again, I've also heard on the wetcanvas forum, that acrylic gesso alone will leave the canvas susceptible to deterioration from the back (because canvas is not sized). The implication for me in this case is that maybe I should use some sort of sizing (PVA, GAC etc.), then acrylic gesso and then the lead ground, for the utmost archival property.

At the end of the day, my question is basically: how to prepare the most archival lead ground without necessarily breaking the bank?

Some guidance would be very much appreciated!

Kind regards,

Péter Hegedűs

Repainting a plaster statue with oil paints

Question asked 2021-02-13 14:35:55 ... Most recent comment 2021-02-14 22:46:45
Oil Paint Other Rigid Supports Sizes and Adhesives

If you were repainting a large old plaster statue (the corpus from an old church crucifix from 50+ years ago) using oil paints, would you apply a sizing? I've been thinking that once I've removed all of the old paint and fixed the fine cracks, I'll use an oil paint primer like those used to prep plaster walls. Does this seem like a good plan? I’d love any advice you could share.​

Sunflower oil?

Question asked 2021-02-14 12:50:24 ... Most recent comment 2021-02-14 21:33:06
Oil Paint

​I live in Turkey and I need to paint now using non toxic materials. For cleaning brushes ,  I am using sunflower oil  will this cause problems. 

flattening a little dimple in an oil painting

Question asked 2021-02-07 23:55:34 ... Most recent comment 2021-02-08 19:32:53
Art Conservation Topics

​I have a oil painting with a s 1/4" dimple in the corner of the painting. There is no noticable damage to the canvas, from the back. The paint is slightly damaged but no paint is missing.

I used a little distilled water on the back of the canvas and about 1/2 of the indention came out. 

I hate to reline the whole canvas to eliminate the indention.

Any thoughts are appreciated.

Dating a vintage copy of Hals Baffoon

Question asked 2021-01-27 12:20:07 ... Most recent comment 2021-02-08 18:52:36
Art Conservation Topics Scientific Analysis Oil Paint

​I have a vintage copy of Franz Hals "Baffoon with a Lute". I would like to estimate the age of this copy.

I have included photos of the stretcher, mounting tacks, back of the canvas, sides of the canvas, and a couple of pictures of the front of the painting.

It was in a frame made in the 1960s, but I think it is older than that. It appears to be in the original stretcher. The mounting tacks are not "blued" and they have rough shaped heads of different sizes.  The back of the canvas is not white but has white spots that may suggest it is soiled. The painting does not appear to have been varnished. It is darker than the original "Baffoon" and has slightly less detail. The decoration on the hat is different than the original "Baffoon".

Any suggestions on how I might date this copy would be appreciated.01 Hals canvas back 1.jpg02 Hals mounting tack side 1.jpg03 Hals mounting tack heads 2.jpg04 Hals front corner and edge.jpg05 Hals front texture of hand 1.jpgBaffoon Front View.jpg

Egg Tempera on Casein

Question asked 2021-01-21 18:32:56 ... Most recent comment 2021-01-29 08:56:29
Egg Tempera Casein

​I have a student wondering if she can paint egg tempera on casein.  Since casein, like tempera, is a high PVC paint, I can imagine it's open, absorbent surface may allow tempera to properly adhere. But I don't really know.  Any thoughts on this idea?

Koo Schadler

casein-acrylic binder as a size for priming linen?

Question asked 2021-01-08 05:47:32 ... Most recent comment 2021-01-25 15:41:08
Casein Sizes and Adhesives Grounds / Priming Oil Paint Flexible Supports

I'm looking for the best way to size my linen, when using a lead-oil ground. 

A combination of Golden GAC 400 en GAC 100, or 2 coats of GAC 200 gives good results. However, I have also tried casein-acrylic binder by Ara Colours ( They are a part of Old Holland.

The descrition says: "Casein acrylic binder V350 is a modern alternative to rabbit glue. It gives a strong flexible film for the preparation of the canvas. Casein acrylic binder is insensitive to moisture after drying."

It becomes indeed very stiff (much more than the GAC 400 or 200) even after a year or so, which is probably due to the casein. This stiffness is very desirable of course, but I also read that casein becomes brittle. Is it possible that this brittleness is counterbalanced by the acrylic? And is casein-acrylic able to block oil absorption? So, can casein-acrylic binder be a good size if you want you painting to last?

I have mailed Ara Colours several times with this question about how it works, but never got an answer, so I hope someone can help me here.

Protein Denaturation

Question asked 2021-01-17 08:28:02 ... Most recent comment 2021-01-19 21:30:04

​Hello MITRA,

I have an egg tempera student with a background in icon painting who makes her medium by combining 1 part yolk with 2 parts wine.  For my class, she changed the ratio to 1 part yolk to 1 part wine (since I work with a thicker medium).   

I'm not a fan of adding alcohol to medium: I prefer just egg yolk and water (cracking a fresh egg as needed; and adding isopropyl alcohol only to the few colors that actually need help dispersing).  The simpler a paint system is the less that can go wrong, and the easier problems are to diganose.  But I realize many painters are used to adding wine or vodka to medium, and of course they are free to work as they please.

This morning her medium, which she keeps refrigerated when not in use, had "curdled". I explained that this is (I believe) protein denaturation: alcohol is causing the molecular bonds in the protein portion of yolk to break down, the same as cooking an egg.  

So, two questions: 

1. Why doesn't this happen everytime alcohol is added to egg yolk?  Does egg oil sort of "encapsulate" the proteins and protect them from the denaturing effect of alcohol?  I understand there is less protein in yolk than in egg white, but still there is some, and clearly (from her example) it's capable of denaturing.

2.  Any guesses what casued her medium to denature?

Hope some of you chemists out there can shed light on this.

the vulnerability of traditionally gessoed ground to water media

Question asked 2020-12-17 05:39:47 ... Most recent comment 2021-01-17 16:13:26
Grounds / Priming Gilding

​Hello Mitra... so happy to have stumbled onto this forum via Koo Schadler's website. 

I've been dipping into the world of water gilding and have a strong desire to begin using it in my painting. 

The process I've been considering and experimenting with is as follows:

Cradling 1/4" plywood panel. 

Coating panel twice, front and back, with Zinser white shellac

After lightly sanding surface applying linen gauze soaked in 15% RSG

application of 10% RSG /Bologna chalk gesso (8-9 coats)

application of white kaolin clay and titanium dioxide white (10:1) with 10% RSG (6 coats)

*But now this is where things get tricky... I would like to paint onto the surface very loosely with water media, (Golden High flow acrylic) before water gilding the whole surface and bringing it to a high polish, then removing the gilding where I want to reveal the under painting, coating it with Golden MSA varnish and a coat of GAC 100 before I oil paint on top of the entire thing.... I know, talk about over-complicating things. 

My questions are:

Does this process raise any red flags for soundness and archivability? Even though loosely water painting onto the kaolin surface does not appear to cause any issues, I worry about the soundness of the gesso after I've wet it? I'm stuck on using traditional gesso because I'm looking for the high polish the kaolin provides. Unfortunately any ready made bole products I can find here in europe aren't white enough.... even with the addition of 1/10 titanium. 

Another concern is the ability of traditional gilding liquor to adhere the leaf considering I've now covered it with a water-thin layer of acrylic? I've noticed on some websites here in Italy that they use fish glue to adhere the leaf after traditional gesso prep. I've since secured some Isinglass (Selinski) and I'm wondering if this is a sound way to adhere the leaf that will allow a true burnish? Should I apply a coat of glue and let it dry, then apply the leaf in a normal fashion with gilder's liquor? Plus I honestly have no idea how to prepare the glue or at what strength I should be using it.

Any expertise and help would be greatly appreciated. Just hoping I'm not completely off my rocker on this one, because I've been working for well over two years to nail this process and I'd hate to give up at this point, but I keep running into archival walls and I'm beginning to doubt that what I want to achieve is doable. 

Patching painted canvas that will be painted over

Question asked 2021-01-09 13:20:07 ... Most recent comment 2021-01-14 20:05:06
Oil Paint

​hi!  I have two oil paintings with scuffed/torn corners.  One is obvious on the actual piece and I would like to paint over it, but am worried that the scuff has gone to the canvas layer and oil may rot the area of the corner.  The other is on the sides of the canvas, but I was hoping to paint all around the sides as well.  Those have definitely gone past the gesso layer and exposed the raw canvas.   The one that is on the image was done in February 2020, and the other in May, although I recently started painting on that one again before I noticed the tears.  

any advice how to safely patch these areas in a timely manner so I can paint over them sooner than later would be very helpful  thank you!


5CF27B39-69A9-4F49-B340-D10287139165.jpegps. I am new to the forums so I apologize if this has been asked. I did search but couldn't find anything on it.

Repairing a Vintage, Plank Backed Picture Frame

Question asked 2021-01-10 17:04:03 ... Most recent comment 2021-01-13 11:24:23
Art Conservation Topics Matting, Framing, and Glazing Rigid Supports

​I am conserving a vintage frame constructed of pine, where the mitered corners have developed gaps as wide as 1/4" and where the frame has warped to about 2" from flat. It is a heavy 36" x 34" frame. The frame had 3/4" pine planks professionally tapered and glued to the back on all sides. 

I had to removed the backing planks to enable closing the gaps on the mitered corners. When I removed the backing planks, the warping was corrected. 

I would like to leave the backing planks off once the frame is properly repaired, but if they were part of the original frame fabrication, I should probably reinstall them. If they were added later to stabilize or strengthen the frame, I would likely leave them off.

I believe the frame was fabricated before 1950. It frames a hand painted copy of Hals "Baffoon Playing a Lute" that was possibly painted between 1880 and 1900.

Question: Do you know of a framing technique where planks are glued and nailed to the back of a frame to provide structural strength, either during original frame fabrication or to stabilize a frame at some later date?

Any recommendations would be appreciated.

Frame Front.jpgFrame Backing Plank Construction.jpgFrame Corner Misallignment 2.jpg


Museum mounting kit

Question asked 2020-12-14 18:11:35 ... Most recent comment 2021-01-11 11:28:05
Matting, Framing, and Glazing Art Conservation Topics

Lineco makes a product called the “Museum Mounting Kit” to make conservative mounting images easier. Do you consider this kit to be able provide true conservative mounting? If so how do think it compares to mounting techniques such as strips and corners that prevent any type of adhesive contact with the artwork?

Using Spray Fix on Charcoal for an oil painting

Question asked 2021-01-03 02:32:26 ... Most recent comment 2021-01-06 17:06:36
Oil Paint


I've heard of painters using spray fix on primed canvas ( (both oil and acrrlic ground) to fix a charcoal drawing before painting on top with oil and have assumed this could be problematic with potential delimination issues, but trying to gauge if this is overly cautious as long as the spray fix is applied reasonably thinly. 

Does Mitra recommend a best practice here for proceeding from a charcoal underdrawing? How is this issue different if the ground is oil based vs. Acrylic gesso? Are there better fixatives suited for this purpose if it is not to be avoided altogether?

Forgive me as I've seen this touched on in these forums, as in here,

but feel like I am still missing info on this general topic here.

Happy New Year- Best, T

Cleaning old and unvarnished paintings

Question asked 2020-12-30 09:58:43 ... Most recent comment 2020-12-30 21:04:03
Oil Paint Art Conservation Topics

​What is the best way to clean old, unvarnished oil paintings in Belgian linen that have been affected by mold, dust, and some bits of paper stuck on some of them? These paintings were covered in glassin paper, parchment paper, and some in Manila paper and have been in storage for years. 

Also, it seems that most of the dusty white and ghostly appearance isn't really mold but something else. This haze effect is visible in the dark areas where the earthy colors are, but never in the lighter areas. Also, the backs of the paintings are very clean. So, I'm not sure if it's mold and how best to address this. I'm seeing so many conflicting advice online.

Note: I'm unable to go to a professional art restorer at this time, so will have to do everything myself. Please help. Would appreciate any advice. Thank you! 134152164_10157907941582358_7668322117097742284_n.jpg 

Cleaning old and unvarnished paintings

Question asked 2020-12-30 09:50:48 ... Most recent comment 2020-12-30 09:47:00
Art Conservation Topics Oil Paint

​What is the best way to clean old, unvarnished oil paintings in Belgian linen that have been affected by mold, dust, and some bits of paper stuck on some of them? These paintings were covered in glassin paper, parchment paper, and some in Manila paper and have been in storage for years. 

Also, it seems that most of the dusty white and ghostly appearance isn't really mold but something else. This haze effect is visible in the dark areas where the earthy colors are, but never in the lighter areas. The backs of the paintings are very clean. So, I'm not sure if it's mold and how best to address this. I'm seeing so many conflicting advice online.. Please help! Would appreciate any advice. Thank you!

Shipping/storing unvarnihed egg tempera paintings

Question asked 2020-12-11 09:27:16 ... Most recent comment 2020-12-17 16:51:15
Egg Tempera Storage Rigid Supports Handling and Transportation Art Conservation Topics

​Hey Mitra!

Does anyone have recommendations for shipping/storing unvarnished egg tempera paintings, especially regarding what material could touch the face of the work?

The works in question have been curing anywhere from 3 months to over a year. 

I considered glassine, but I imagine little creases or folds in the glassine could become abrasive. A thick poly was the other option I was thinking...

Always very grateful for the responses I get on this awesome forum. thanks - eli bornowsky

Reducing absorbency of acrylic primer

Question asked 2020-12-13 10:56:03 ... Most recent comment 2020-12-14 15:13:47
Rigid Supports Sizes and Adhesives Flexible Supports

I'm using an acrylic primer to prime an MDF panel for subsequent (possible) acrylic underpainting, then ultimately oil painting.​ I've previously had problems with such surfaces "grabbing" the brush, making it almost impossible to blend paint nicely, as well as the paint drying out very fast/oil colors sinking in. I've heard two different bits of advice:

  1. Use PVA to seal the primer by applying a thin layer. 
  2. Use egg white, spreading it thinly and allowing to dry before painting.
I've tried acrylic medium before, but I found that it didn't improve the brushability all that much, it still has a certain "grab" to it.
Would either choice be better? Also, would the same advice hold for flexible support?


Question asked 2020-12-14 00:24:34 ... Most recent comment 2020-12-14 12:43:27

​Iis it ok to spray fixative on drawing paper BEFORE I do the pencil drawing? Reason: I like the graphite, which I use in tones, not lines,,to be be sometimes brushed to make lighter areas and also. I dont use workable fixative to do this but final fixative, and also to make the drawing easier to erase 

repair split at side of oil painting

Question asked 2020-12-13 07:53:42 ... Most recent comment 2020-12-13 17:35:39
Art Conservation Topics Oil Paint

​A painting of mine got into a show and I just noticed a weakening and the beginning of tearing at the back/side of the canvas. Can this be repaired without strip lining? And if so, how.

Water Block on Gesso

Question asked 2020-10-21 11:26:55 ... Most recent comment 2020-12-11 09:30:26
Animal Glue Egg Tempera Grounds / Priming Rigid Supports

​Hello Mitra!

I wonder if anyone here has experience with "water blocking" traditiona gesso on panel? I've seen very little about it, but I've read some suggestions that a gesso panel could be smoothed by working the surface with a hardwood block dipped in water.

It's hard for me to imagine this method fully removing brushstrokes, and I would worry that the paste worked up by the wet block would be unstable.

That said, the intorlerable amount of dust created sanding larger gesso panels has me searching for alternatives.

Perhaps an old school scraping method combined with a wet block?

If anyone has experience or resources to share on this topic, I would love to hear about it. Thank you

- eli bornowsky

Varnish beading up in places, on acrylic?

Question asked 2020-12-08 16:25:50 ... Most recent comment 2020-12-09 08:00:28
Acrylic Art Conservation Topics Scientific Analysis Varnishes

Hi all,

I recently varnished two paintings I completed that were in acrylic. One was in Golden OPEN which I had left to dry for several weeks and with using undiluted Gamvar Gloss it varnished beautifully with no issues.

The other painting was done with Amsterdam Standard and Liquitex Basics Acrylics (So not craft art products) that I left to dry for 2-3 weeks. But to my surprise I found that I had beading in some areas as I would with oil paints. I scrubbed with the brush to reduce the surface tension until the varnish applied properly (or mostly).

Still, I was surprised as I've not had this happen with acrylics before and I assumed that the relatively open surface (compared to oils) meant that beading couldn't occur.

Have you had this experience before when conserving acrylic paints? Is there anything you recommend I could do in the future to avoid this? It was interestingly how the other painting was completely fine though. Would it be the difference in the resins between the different companies products that contributed to this? If so, then perhaps an isolation coat with GOLDEN mediums (following their guidance) would resolve this?

Just interested in your thoughts..

Richard Phipps

Canvas on Masonite

Question asked 2020-12-08 21:57:57 ... Most recent comment 2020-12-08 22:14:51

​I want to adhere pre-primed canvas to masonite panels using acid free PVA glue. The panels are smooth on both sides.  Can I simply glue the canvas directly to the masonite as is or do I need to prep the surface in any way such as cleaning, sanding or priming?  (When I adhere canvas to plywood I seal it on all sides with pigmented shellac and then use acid-free PVA glue to attach the canvas so I may be just over-thinking this.)    

impasto oil rises to the surface

Question asked 2020-12-07 20:56:40 ... Most recent comment 2020-12-08 21:30:30
Oil Paint

​Many of my paintings are done in thick impasto oil paint using stand oil. I have done some testing (2 years ago) using different stand oils in impasto oil paints. I have noticed the oil rises to the surface and yellows slightly. When the dried oil is cracked open the paint is a bright white inside. I have tried poppy oil and even though that rises to the surface it does not yellow, but I noticed the paint is more brittle than those done with linseed/walnut stand oil. So my question is how to prevent the oil rising to the surface? Would bees wax help, or possibly add other issues.

slow drying of thick impasto

Question asked 2020-12-07 23:07:54 ... Most recent comment 2020-12-08 09:16:31
Drying Oils Paint Mediums

​How do you slow the drying of thick impasto oil paint (stand oil added as medium) to allow it to be worked for several days? I know pigment selection is crucial, as well as temperature/light exposure. Maybe spike oil substituted for odourless solvent, a less absorbent acrylic ground, may help. Poppy oil does help but the dried paint film is more brittle (from testing of samples). Am I asking the impossible to extend the drying time of fast driers like cobalt blue and also for it to remain flexible. I even had a box made to store the painting overnight with cotton balls soaked with clove oil, but this puts size restraints on the painting size.  I seem to solve one issue to just raise another one. Any thoughts would be appreciated.

varnishing on oil paint necessary

Question asked 2020-12-03 22:23:47 ... Most recent comment 2020-12-06 08:36:40

​I was inquiring if it is necessary to varnish oil paintings. I understand varnish can protect against UV light, dirt and abrasions, but I use very thick impasto oil paint. From what I understand it can take many years to dry. I add a stand oil to the paint, so the surface of the paint has a relatively even sheen upon drying so aesthetics is not an issue. From a conservation point of view is it best not to varnish, or varnish at about 3-6 months (probably with Gamvar). Does Frank Auerbach's work have problems as I do not think he varnished his paintings?

Cold Wax Medium as Varnish

Question asked 2020-12-04 14:43:35 ... Most recent comment 2020-12-04 15:31:03

​Can Gamblin's cold wax medium be applied to a painting as a final varnish? Will it provide adequate protection? I love the soft luster it provides. 

What to do about pinholes in oil on linen picture

Question asked 2020-12-01 08:25:56 ... Most recent comment 2020-12-01 22:10:34
Oil Paint Flexible Supports Art Conservation Topics

Question: Should I resize an oil on canvas after pinholes appeared?

I am a traditional oil painter working in San Diego. I've worked on the same picture for several years. The work is done on Claessens oil-primed Belgian linen, relatively thin and smoothe. I recently scraped the upper layers of paint off an unsatisfactory section (down to the tone ground).

Small, translucent areas and pinholes appeared (hardly surprising). 

I'm concerned the canvas could rot from direct contact with the paint. Two contacts in the industry have told me (1) the animal glue sizing penetrated the fibers, such that the risk of rot is minimal, and (2) I could apply animal glue size to the entire canvas from the reverse, but need to guard against uneven tension, warping, etc.

At present I think leaving it alone is best. I'll repaint that section and hope it doesn't rot.

Your thoughts on the matter will be appreciated.

Combining Organic and Non-Organic pigments to improve Lightfastness

Question asked 2020-11-26 08:16:25 ... Most recent comment 2020-12-01 18:21:41
Pigments Scientific Analysis Technical Art History

​Hi all,

From what I understand about pigments and from what I have read in articles from the paint coating industry, some non-Organic pigments have the ability to absorb rather than reflect UV light and without being so affected by the UV rays as most organic pigments can be.

I am thinking here of Iron Oxides, Nickel Antimony Titanium Yellow Rutile (PY53), and Chrome Antimony Titanate (PBr24) .

I believe from what I have read that the paint coating industry offer mixes of inorganic mineral pigments like this with much more chromatic organic pigments to improve lightfastness as well as opacity and reduce cost.

Am I correct in this assumption, and that if I mix say PY74 with PY53 (which is a weak tinter), or PR254 with PR101 I will improve lightfastness of the organic pigment on it's own at the expense of Chroma?

Thank you for your help,
Richard Phipps


Question asked 2020-12-01 06:04:33 ... Most recent comment 2020-12-01 06:44:58
Industrial and Non-Traditional Products

​hi I just wondering that I can use gilsonite or bitumen for house decoration and does it have a harmful point or not?

Zinc White (PW4) issues

Question asked 2020-11-23 11:50:16 ... Most recent comment 2020-11-24 07:09:57
Pigments Egg Tempera

According to recent research, zinc white (PW4) causes saponification in connection with oil paints. This means zinc white can cause long-term damage to the image. Is this also the case with zinc white and egg yolk tempera?  And how does it look like in connection with tempera grassa?

B-72 Application

Question asked 2020-11-20 09:39:59 ... Most recent comment 2020-11-22 15:08:14

Because the solvent (xylene) in my B-72 is noxious, I've been applying isolating layers in a unheated room above my studio - it's not freezing, but can get into the 40 degree F. range at times.  ​Anyone know the ambient temperature range at which one can safely apply B-72?



Question asked 2020-11-12 11:04:40 ... Most recent comment 2020-11-17 13:54:29
Paint Making

every now and then, when I am making my own oilpaint, the paint gets too stringy. I'll add some Omyalite and/or some beeswax dissilved in oil, but that seems to help only a little.

What an I doing wrong? Is it perhaps the not-premium linseed oil? Is Omyalite not the right thickener?

Thanks in advance

MSA added as oil paint medium

Question asked 2020-11-07 12:51:11 ... Most recent comment 2020-11-10 18:09:57
Oil Paint

Hello –

First, thank you MITRA for providing such a wealth of information and expertise. I have greatly improved my craft by reading your resources and forums.

My question is not addressed in your resources articles. It is: can MSA (acrylic which is not water-based) be added to oil paint with no appreciable archival concerns? The scenario I am thinking of is if the oil painter paints thin and allows the surface to be touch-dry before applying the next layer. If this is possible, I think it would help in achieving one of my goals in terms of perceived depth and luminescence, similar to Maxfield Parrish, but lasting longer.

At least one commercial provider, Lukas, offers it, albeit with dammar, and it is advocated in other art technical materials discussions.

If it is possible, what are the other process steps or materials which need to be considered?

Thank you. 

Mediums for oils

Question asked 2020-10-30 13:08:19 ... Most recent comment 2020-10-30 21:14:44

​Hello again! When I use mediums is it best to stick to one type at the beginning? We experimented with an oil butter, sand and other stuff for a cool texture. 

Appropriate Substrate Material for Mounting Pastel paper (Roll)

Question asked 2020-10-26 16:47:52 ... Most recent comment 2020-10-30 15:19:12
Rigid Supports Sizes and Adhesives Pastel

​I am looking for an appropriate mounting surface for a 4' x 6' pastel paper. If I were to mount this on an aluminum panel what is the best way to do this? Using paper mounting hinges or an adhesive of some sort? I am not sure how the aluminum surface will react to adhesive. Also should the aluminum be specified to have a desired topical finish? Thank you for your time and look forward to hearing from you. Maria Marino

OIl painting for beginners

Question asked 2020-10-30 13:01:41 ... Most recent comment 2020-10-30 12:59:00

​I am new to oil paints and jsuyt started a course which is fab but I have so may questions about how thick oyu should apply the paint, what tools make the best mark making (i.e. spatulas, or brushes) and how many layers should I start with please? Thanks

Marble dust and Oil paint

Question asked 2020-10-26 09:06:15 ... Most recent comment 2020-10-26 17:50:48
Oil Paint Paint Mediums

I want to add body to my oil paints, so I was researching about mixing marble dust with linseed oil and use that as a medium.

I don't have access to a lot of variety, fine art materials wise, so that seemed like a simple enought option.

I have a few of questions though:

1-Would it be better to just use linseed oil or would stand oil be a better alternative?
2-Could I use that mix in the initial layers, and then on the next layers use just pure paint? Or would I have to up the ammount of oil content for the next layers?

3-What ratio should I aim for? The consistency should be of pure oil paint from the tube?

Thank you!

Fat Over Lean Solvent Free?

Question asked 2020-10-24 17:28:45 ... Most recent comment 2020-10-25 21:02:59
Oil Paint

​If I paint solvent-free with oil paint straight out of the tube for my first layer, and let that dry to the touch for my second layer, and so on for subsequent layers, do I have to make each subsequent layer fatter by adding a little oil to my paint nuts, assuming I use no solvent ever? Or since there is no solvent do I not have to make each layer fatter? Thank you.

Erasing charcoal, pigment or pastel stains

Question asked 2020-10-23 17:27:43 ... Most recent comment 2020-10-24 19:41:40
Drawing Materials Art Conservation Topics Other Pastel Studio Tools and Tips Watercolor

​A student just completed a wonderful charcoal drawing on Lanaquarelle watercolour paper. Unfortunately, she smudged it by holding it with her hands covered in charcoal dust. She tried to erase the stains, first with putty eraser, then with a normal eraser and finally with an electric eraser. The stains are still visible, as the paper is quite porous.

Do you have any suggestion on how to bring the whiteness back to the paper? Or is there any paint that looks exactly like the paper? We even thought of putting some soaked off-cuts of watercolour paper in the juicer, add some matte acrylic binder and apply it thinly over the stains!

Thank you

Primeing ACM panel

Question asked 2020-10-23 10:04:09 ... Most recent comment 2020-10-23 10:55:16
Oil Paint Rigid Supports Grounds / Priming


Would it be good practice to apply a layer of titatnium white mixed with an alkyd or cobalt dryer, on top of an acrylic polymer ("gesso"), when priming an ACM panel?

I'm a painter from Brazil and fine art supplies are hard to come by here. Ideally, I like to paint on oil-primed linen mounted on ACM panels, but linen, when you can find it here, is ridicoulosly over priced. Think like 4 times what you would pay in Europe or US.

So I'm priming my ACM panels with an acylic polymer ("acrylic gesso"). I sand it lightly and then apply up to 5 coats with a brush roller.

It is a fine surface to use, but I find that is too absorvent and the oils sink in way too much. The paint doen's flow as well and the darker colors become way too light the next day, making it impossible to judge it's values.

So a fellow painter reccomended the titatnium white with a dryer.

Would that be ok? What should be the ratio of paint to dryer?

Thank you!

Making paint with polyurethane

Question asked 2020-10-08 17:32:35 ... Most recent comment 2020-10-22 18:00:13
Alkyd Acrylic

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I am trying to make paint for art paintings on wood and paper and canvas using polyurethane (water based) Sherwin Williams as the medium/binder.

The support people at SW said nothing should be added to it by way of colorant and not  to thin it with anything, even water, as that would weaken the paint film.; (a legally safe response.)

Since the clean up directions for use said to use warm water immediately and the stuff was ‘water based’  the clerk in the store and I thought thinning with water could be done,  like the use of water in acrylic thinning where its okay if you don’t use too much.

I think I saw on some SW literature that  a wood stain could be added to the polyurethane.

I also see that the polyurethane will yellow over time , and as a matter of fact, it looks yellowish right out of the can.  I think I can live with that.

The main question is;

What are the potential or probable effects of using acrylic paint as a colorant in the polyurethane.

So far I have mixed and used some mixtures like this and also with powdered pigments, but  it has not been long enough to tell much of anything, except that they do dry pretty fast and the mixture seems stable enough over a couple of days if covered on the palette..

Kindly advise if this is a dead end, or a guess as to what bad and good things I should look out for.

Thank you.

Thanks for help with acrylic/alykd question

Question asked 2020-10-22 17:58:42 ... Most recent comment 2020-10-22 17:53:00


Please excuse the delay in responding to the very helpful answers to my original question about mixing acrylic/alkyd mediums together - dealing with the damages from Hurricane Delta is taking a lot of my time.

Thanks to Brian Baade,Matthew Kinsey and George O’Hanlon, you have provided a couple more possible strings for my bow in the hunt for the best medium for me.

organic pigments... Not lightfast?

Question asked 2020-10-21 10:18:25 ... Most recent comment 2020-10-22 14:01:07

I found this article on natural pigments about the lightfastnes of organic pigments. Time to panic?

Sennelier Egg Tempera and Acrylic Gesso panels

Question asked 2017-03-08 11:44:47 ... Most recent comment 2020-10-20 20:13:11
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?

Absorbency characteristics of a lead oil ground?

Question asked 2020-10-17 06:36:52 ... Most recent comment 2020-10-20 03:33:35
Grounds / Priming

Hello all,

I am currently involved in a painting project consisting of 12 identically sized HDF panels (approximately 5" x 8") each of which have been prepared with slight textural differences (linen, cotton, or a collage of linen fabric all attached to the sized substrate with rabbit skin glue) or in a few cases, acrylic sculpting gel applied to the substrate over a few light coats of acrylic gesso. All these individaul treatments - each of which follow a preconceived design - preceded the two "final" coats of white lead primer (I used Old Holland "Cremser White" from a tin, which I understand is industrial lead carbonate ground with cold-pressed linseed oil. I thinned it to flowable consistency with five parts turpentine and one part stand oil). This primer was applied and cured for one year. (Not my plan to wait that long, it's just what happened)

Now I am beginning the painting process. To reiterate, the central idea for these panels is/was to paint in oils over a traditional white lead oil ground - with this variety of textural interventions - and see what kinds of effects occur. So, I'm entirely open to fortuitous visual accidents, but at the same time I do not want my experiments to result in lack of adhesion or longevity. 

Thus, my question/conundrum: the ground does not appear to be as absorbent as I might expect. Is this normal? This week I've done a very light, thinned imprimatura in yellow ochre over all twelve and let it dry three or four days. Then I transferred my design with charcoal and reinforced it in mars black (tube oil paint) heavily diluted with turpentine. I let these underdrawings dry two or three days. They look very good, but when I used a kneaded eraser to lightly remove the charcoal lines from my transfer I can see both yellow and black on my eraser. Not good, I think. Should I have waited longer for both of these underlayers to dry? They were certainly dry to the touch. Or did I make a mistake at the get go? Should I have thinned my lead primer with more turpentine and eliminated the stand oil?

I'd appreciate your thoughts or suggestions. Of course, if I need to, I can start over; recreate some of my textures, paint in oils over an acrylic gesso ground and chalk this one up to experience, however I am curious about the benefits of painting in oils over an oil based ground.

Thanks in advance for your insights.


Ellen Trezevant

Technically sound way to do wipeout friendly ground and isolation layers

Question asked 2020-10-19 12:07:30 ... Most recent comment 2020-10-19 12:30:12
Grounds / Priming Oil Paint

I am getting very frustrated with my method but can not find the best way to fix things. I use hardboard primed with Gac100 and either Gamblin oil ground/Rublev alkyd/Wiliamsburg lead. Wait 3-4 weeks and apply a light tone of raw umber and Gamsol, wait 3 days. Start painting with unaltered tube paint, make a mistake and try to wipe it, the wipe takes off the tone and the white ground underneath is now stained. 

Ideally, I would like to have a very light tone or just white board and 2-3 painting layers on top, wiping as I go without damaging or staining what's underneath. I thought the tone was under bound but putting a richer tone was not recommended. I thought the ground was too absorbent but having a more closed off ground was not recommended either.

I'm sure I'm not the only artist trying to do this but I can't find a good example to follow. Maxwell Parrish supposedly used retouch varnish but everyone says that's a no go. Rockwell and Brad Kunkle use shellac and Richard Schmid says his lead oil ground allows him to wipe back to white but I am not able to replicate this with unaltered manufacturer grounds I tried. Please help.

Final Varnish new product help please!

Question asked 2020-10-12 16:35:05 ... Most recent comment 2020-10-17 20:50:30

​I used Old Holland Gloss Picture Varnish (made from ketone resin) on an oil painting as I was looking for a nonyellowing product.  It is too glossy.  Neither the supplier nor Old Holland can tell me if I can do a second layer with their Matte Picture Varnish without losing clarity.  Has anyone used these products?  

Mixing oils and alkyds

Question asked 2020-10-08 02:46:25 ... Most recent comment 2020-10-09 02:58:14
Alkyd Oil Paint

Kindly advise:  I work in oils, but rely heavily on alkyd paints to improve drying times.  I don’t mean alkyd mediums such as Liquin, but actual alkyd paints such as the W&N Griffin range.  According to W&N, it is acceptable to use alkyds for underpainting, and then work with regular oils over alkyds.  I take this a step further.  My underpainting is pure alkyd paint, and for the subsequent layers I mix alkyd and oil paints together.  I mix a bit of alkyd white with oil white, a bit of alkyd black with oil black.  These hybrid mixtures are then used to mix other colours which dry fairly quickly.  The upper layers of my paintings consist of pure oil paint, with some medium added to follow the fat-over-lean rule.  I should mention that I work on rigid supports, usually on a Gesso ground.  Can anyone foresee any issues with this technique?  Your advice would be appreciated!

Delamination of 1st or 2nd color layer while applying a couche

Question asked 2020-09-26 21:23:41 ... Most recent comment 2020-10-05 14:18:18

​Hello Everyone,

I find that when I need to apply a couch to paint into to merge my layers and match my value, sometimes my previous color layer starts wiping off, destroying hours and hours of previous work. This never used to happen when I was more reckless in my early years. But now I paint solvent free and use as little medium as possible. For context I paint on museum quality gesso board (acrylic ground). I use lead white and typically do my underpaintings with a mars color and white or old Holland raw umber. Sometimes I seal my drawing with acrylic matte medium, sometimes just a light layer of raw umber and lead white. What I can't seem to figure out is if my under layers are underbound or if the couche I'm applying is the cause of delamination. It was my belief that a couch would not only make each new layer fatter but INCREASE adhesion and not the opposite. I typically use oleogel or walnut gel as a medium. Does anyone know what could be causing this issue?


Question asked 2020-09-29 09:44:55 ... Most recent comment 2020-09-29 18:52:44
Health and Safety

​What are the health issues with being pregnate or having an infant in art schools or home studio? 

Golden Acrylic paint: pigment concentration

Question asked 2020-09-15 05:57:19 ... Most recent comment 2020-09-17 10:38:34
Acrylic Pigments

​Hi to the MITRA team,

I have questions about the pigment concentration (pigment load) of the Golden Paint line.

There are four viscosities in Golden paints (heavy body, soft, fluid and high flow acrylic) and I would like to know if there are differences in the pigment concentration between the Golden acrylic range.

I understand that the polymer binder used is the key to the consistency of the paint, but strictly speaking about the pigment concentration, what is the most loaded paint?

It is said in the description of the Golden paints that they contain no fillers or extenders, does it mean that the paint is fully pigmented as in some high quality oil paints?

If I want to extend acrylic paint while maintaining the most of the saturation, what should be the optimal dilution factor?

Thanks in advance,


Use of eggwhite in oiling out mixture

Question asked 2020-08-29 09:19:42 ... Most recent comment 2020-08-30 00:24:38
Drying Oils

​Dear MITRA I have been reading about using a mixture of sun thickened linseed oil and egg white to oil out the painting surface at least initially (before the first layer; I'm not sure if my source recommends it between subsequent layers or not) and am wondering if this presents any problems as regards the stability of the paint film long term? 

Restoring color to a shellacked totem pole

Question asked 2020-08-13 13:55:17 ... Most recent comment 2020-08-28 08:28:30
Acrylic Alkyd Art Conservation Topics Dyes Grounds / Priming Industrial and Non-Traditional Products Oil Paint Other Paint Additives Paint Mediums Pigments Solvents and Thinners Varnishes

​I have a custom made totem pole that is over 20 years old.  It has been shellacked a few times in an effort to preserve the wood. Although this seemed to work, the colors have darkened and disappeared.  I am trying to restore the original colors and need advice as to what type of paint products to use. Would appreciate any advice. 

Russian Sauce vs Soft Pastels vs Watercolour

Question asked 2020-08-24 19:56:05 ... Most recent comment 2020-08-25 14:56:08
Pastel Watercolor Drawing Materials Ink

I’ve been curious about Russian sauce and its use in drawing. I see that some artists enjoy applying washes of this medium on their drawings. Is there any advantage of Russian Sauce when compared to washes made with powdered soft pastels or watercolour? And what’s the best brand of Russian Sauce? I only seem to find Yarka and no info about lightfastness? Thank you

ratio of Regalrez 1094 resin to solvent

Question asked 2020-08-21 21:34:31 ... Most recent comment 2020-08-22 20:21:45

​I have Regalrez 1094 in resin form, and i need to know the proper ratio of resin to solvent. I would like to limit the size of the resulting mixture to about 2 oz. per session. I do have Tinuvin 292 to add to the resultant mix.

Matting Agent

Question asked 2020-01-06 11:15:30 ... Most recent comment 2020-08-09 12:34:56
Paint Additives


Do you know specifically what substance(s) are added as matting agents to matte varnishes and mediums?   

Thanks, Koo

Golden fluid Tg

Question asked 2020-07-05 06:36:53 ... Most recent comment 2020-08-07 16:22:07
Art Conservation Topics Acrylic

Hello forum,

does anyone know what is the glass transition temperature of the Golden fluid acrylics?

I NEED HELP IDENTIFYING A "Dutch Oil Landscape Painted on Copper"

Question asked 2020-08-07 10:59:43 ... Most recent comment 2020-08-07 11:48:09

​Hello, I am hoping someone can give me some tips or adivce on the best way to identify the artist and name of a painting. My friend was given a painting through probate. The issue is that certificate on the back is missing (you can the square the patch on the back of the where the certifcate would be. The painting has no artist signature. 

All the info we have have is that it is a "Dutch oil landscape" and it is painted on copper.  I belive it is an orginal becuse it purchased 30 or so years ago from an auction house in New Orleans. However, the auction house has changed ownership 4-5 times since then and they do not have the records from 1995.

Please see the links below for pictures of the painting. Any help would be much apperciated!

acrylic retarder

Question asked 2020-08-06 02:57:55 ... Most recent comment 2020-08-06 10:40:48
Paint Mediums Acrylic


Hello Mitra, I have a bottle of propylene glycol and I am going to use it as a drying retardant.

I have read and tried different brands of retardants and each of them gives different ratios.

I assume that each brand uses different products and different dilutions.

-How much propylene glycol is safe to form a good paint film?

-Is there a more effective product than propylene glycol apart from using golden open gel medium?


Oil paint failure

Question asked 2020-08-01 14:52:48 ... Most recent comment 2020-08-02 16:32:00
Art Conservation Topics Grounds / Priming Oil Paint

Hi all,

I've just come back from Mallorca, Spain visiting my parents in law. I noticed one of the paintings they had in their house had quite substantial cracking (mostly in light areas.. zinc white?) and paint adhesion failure.

The painting was dated with the signature to 1944 and received a lot of indirect (or direct) sunlight and high temperatures.

I just thought it was interesting how badly the paint film was doing. I'm not sure if the canvas was primed correctly either?



Question asked 2020-07-15 05:15:01 ... Most recent comment 2020-07-17 20:16:38


Hello Mitra, I have been experimenting with  AM (Kremer) alkyd resin not only to make paint but to make a medium and putty.

-Using the raw resin the paint becomes unusable in a matter of minutes.

Only when the resin is diluted in approximately 20% resin 80% normal linseed oil does the paint have desirable properties.

The same thing happens when I make a medium that becomes sticky in no time if I don't add oil.

My questions are:

1-Is it normal for this to happen?

2-When manufacturers name a line of paints as alkyd, is it possible that they only contain a very small fraction of resin?

I love the work that you are doing.

Thank you.

Acrylic gesso's opaque pigments

Question asked 2020-06-27 01:42:06 ... Most recent comment 2020-07-14 15:27:33
Acrylic Grounds / Priming

​It seems logical to suppose that the only opaque white used in the art market's acrylic gesso is titanium white, with no zinc white.  Is this a safe presumption?  I'm looking to reassure myself that there's nothing in these grounds for absorbed oils to react with.


how to chose glass railing spigot?

Question asked 2020-07-13 06:38:25 ... Most recent comment 2020-07-13 14:30:36
Matting, Framing, and Glazing

Hi all,

I don't know if this question should be show in this cagegories if I am wrong, I am sorry.

My question is about the glazing and glass, about the glass railing spigot? As you known, there are many different kinds spigots, if build a new glass railing, chose the stainlesss steel or the brass one? which one is better? who can tell me? thanks very much


What Size for Casein Ground on Rigid Support

Question asked 2020-07-03 08:39:29 ... Most recent comment 2020-07-05 13:34:05
Sizes and Adhesives Grounds / Priming


New to this I'm sorry if this has been asked before. Sometimes I use casein paint as a ground on rigid supports like hardboard to paint with oil colours on top. Also under it I tend to use rabbit skin glue as a size (or a transparent acrylic 'gesso' which I have found it to be a great sealer) Just wondering if the size layer is necessary...or if just few coats of skim milk might be enough to act as a size?

How are professional poster color paints made?

Question asked 2020-06-26 20:02:27 ... Most recent comment 2020-07-03 15:54:47
Paint Making Gouache

I read: 

And contacted a few manufacturers, but they gave me very little info, other than that they have "extender pigment" and other additives. So not just gum arabic with pigment. 

I'm wondering if there is a poster color medium out there that I can just add a pigment dispersion to?  

I was recommended to come here from reddit, so first post! 


Acrylic primer cleaning

Question asked 2020-06-23 16:50:42 ... Most recent comment 2020-06-26 17:33:09
Oil Paint Acrylic Grounds / Priming

​If acrylic is more vunerable to the solvents used to clean oil paint and remove varnish.  How should one guard against future damage on an oil painting applied over an acrylic primer?

Is it enough to cover the entire acrylic surface with oil paint?

What if an artist wishes to have gaps in the brush work. leaving blank white acrylic primer spaces?  Is this safe?  Should they reprime with a white oil paint first?


Oil paint directly on top of PVA size

Question asked 2020-06-24 16:35:57 ... Most recent comment 2020-06-25 22:24:23
Oil Paint

​A well know painter recently stated he uses Gamblin PVA size to seal his drawing on acid free 270 gsm smooth paper. When dry, he adheres the paper to a sealed rigid substrate. Then he paints directly over his drawing with oil paint. Is there any known problem with this method and does PVA seal the paper from the oils? Can oil paint adhere well to the PVA? Would it be better to seal the drawing with casein based fixative instead of PVA? 

Hands on drawing paper

Question asked 2020-06-24 15:42:37 ... Most recent comment 2020-06-25 18:43:39
Drawing Materials Handling and Transportation Pencil Art Conservation Topics Flexible Supports

​Hello dear people from Mitra!

I have a question about paper safety while drawing. 

I am really trying my best to put some paper beneath my arm(hand) while i am drawing so i dont put my bare hand on drawing paper.

But sometimes when i want to  put it aside, i touch it with my bare hands.  And sometimes my hands get a bit sweaty, but this lasts only few seconds...

The papers i use are thicker watercolor papers and are Acid Free, but i wanted to ask will these few direct contacts with paper and with barely sweaty hands cause a big problem? 

Thank you

Hansa yellow light (PY3) lightfastness in mixtures

Question asked 2020-06-23 01:28:13 ... Most recent comment 2020-06-25 06:52:32

​Dear MITRA people. I have a large amount of Gamblin PY3 oil-based etching ink but have been reading recently that the lightfastness of this pigment is questionable. On further reading about it in the Just Paint newsletter from Golden in an article from 2018 about changes to their yellow range in acrylics, it seems that this poor rating is based on its behaviour as a tint when mixed with titanium white and it was suggested that there might be some sort of adverse synergy going on between them in acrylics. 

This article however also mentioned that it was performing well in oils (and strangely, watercolours). I do know lots of oil painters who feel it should be avoided, What is your opinion of the lightfastness of this pigment in oils (whether paint or printmaking ink) and would it be fair to imagine that if I use it in mixtures that don't include a white, it should be reasonably reliable? 

Preservation of Acrylic on Watercolor Paper

Question asked 2020-06-11 17:18:01 ... Most recent comment 2020-06-23 19:49:18
Acrylic Art Conservation Topics Varnishes

Should acrylic on watercolor paper be framed under glass? If so, why? The paint application was very watery, like watercolor paint. I used Golden Fluid acrylics. Or, does a varnish suffice? Thank you.

How Archival Are Acrylic Paintings?

Question asked 2020-06-19 20:20:42 ... Most recent comment 2020-06-23 19:46:47
Acrylic Art Conservation Topics

​I have read claims by amateur artists that because acrylic paints are "plastic" they will last forever and never crack or delaminate. I quite enjoy painting with acrylics and am curious what we actually know from experience or research, or can infer about the longevity of acrylic paintings. There are so many ways to use this versatile medium that I also wonder whether how you use it affects its archival properties. Thanks for your thoughts.

modern alternative to collagen for a flexible gesso?

Question asked 2020-06-19 16:28:48 ... Most recent comment 2020-06-21 20:44:47
Grounds / Priming Animal Glue


I am happy to have found this science-oriented forum (through koo schadler's site), and I have a few questions to ask.

I did silverpoint some years ago on traditional gesso (rabbit skin glue and whiting).  I am getting ready to do it again.

I observed then, that while traditional gesso is pretty hard, it is brittle and requires that rigid support.  I just asked natural pigments how "silverpoint on prepared paper" cited in museums catalogues of renaissance silverpoint drawings even worked, without flaking off the page.

Natural pigments replied that paper usually meant vellum, which was a little stiffer than what I was thinking of.  They also replied that these drawings were mounted and preserved from a very early year, and not subject to that much bending and flexing.

it's 2020.  I'm wondering if there are flexible, and archival, substitutes, that would make a more flexible gesso less likely to crack?

I am also already looking into alternatives to whiting, which is only a 3-4 on the mohs scale, and just barely hard enough to scratch annealed silver.  I'm thinking, 1200 grit aluminum oxide polishing rouge, 1200 grit silicon carbide (for goldpoint-- it's grey), or 400 mesh silica flour, all of which are much harder than ground whiting.  I don't see any reason they won't work! (but if there is a reason please tell me :) )  One is budget, but I live in hawaii now so the price difference between whiting and alumina is much diminished after shipping.  I miss just walking to a pottery store and paying $15 for a big bag of whiting...
Except crystal structure IF I was planning to use gold leaf, then you need a planar silicate that will lie flat so it is burnishable.  but that's what bole is for.  

commercial alkyd primers?

Question asked 2020-06-19 16:38:55 ... Most recent comment 2020-06-19 17:17:40

In preparing my own canvases, is there a commercial alkyd primer you would recommend?  (e.g., home depot, sherwin williams).

To add to the confusion, some commercial alkyd paints have added polyurethane, or even added silicone (considered the more premium choice).  Unsure how those would affect linseed and safflower oil layers of traditional paint on top.

Oil paint on "semi-primed" cotton/linen

Question asked 2020-06-19 10:01:06 ... Most recent comment 2020-06-19 16:15:24
Oil Paint Sizes and Adhesives

​Francis Bacon painted on the back of a primed surface. Are there any concerns with this approach given that one side is properly primed PVA,oil ground etc.

Many thanks

Pen for signing oil paintings?

Question asked 2020-06-16 15:10:24 ... Most recent comment 2020-06-19 00:12:07
Oil Paint Varnishes

​A woman I know wants to sign her oil painting using a pen/marker that is compatible. Obviously, acrylic-based markers would be bad! (Acrylic doesn't adhere well to oil paint film.) I’m wondering though, about enamel-based pens. Or Pebeo has an oil pen that uses a synthetic mineral oil as the base.

Byeond simple good adhesion, the other concern is the pen/marker holding up to varnishing and later removal of said varnish.

hardware store linseed oil

Question asked 2020-06-03 18:22:50 ... Most recent comment 2020-06-16 17:31:25
Drying Oils

​One of my students informed me that he is painting using boiled linseed oil from the hardware store. I advised against it. Did I give him the right advice and what is the problem if any with using generic non artist grade linseed oil to paint with?

Silverfish eating my egg tempera painting

Question asked 2020-06-14 15:46:22 ... Most recent comment 2020-06-15 23:35:25
Egg Tempera

​anyone experiencing e with silverfish eating tempera paint from the painting?


Reducing Zinc in Whites by Mixing Different Types

Question asked 2020-06-07 10:10:11 ... Most recent comment 2020-06-10 02:20:20
Oil Paint

I am aware that it is possible that Zinc Oxide can cause delamination and cracking in oil paint layers.  Unless there is some new information I missed, apparently there is no known safe amount of Zinc Oxide in the paint that will stop this for sure. I have read that less Zinc content is logically better if you do want to continue to use Zinc Oxide containing oil paint. I would appreciate hearing the latest from any of the moderators here who might want to comment on the following. 

I have a large volume of Titanium White oil paint that has a Zinc Oxide content of 15% or less. I am not really wanting to throw it all away. I have decided to use that what only on rigid supports, but would also like to reduce the ratio of Zinc Oxide in it, if I can. Would it be worthwhile to mix existing Titanium / Zinc whites that have higher ratios of Zinc Oxide in them such as a known 15% maximum with Zinc free white paints and are there any lead free pigments such as PW5 / Lithopone or PW21 / Barium Sulfate that might be more apt to help reduce delamination and / or cracking? 

On the same topic of the possible problems with Zinc, would it be advisable to avoid using acrylic underpainting layers when using Zinc containing oil whites? How about using oil grounds vs acrylic dispersion grounds with the same whites? And lastly, does the thickness of the layer containing the Zinc Oxide have any impact on the potential for cracking or delamination?

Thanks in advance for your input.

What wood is suitable for painting?

Question asked 2020-06-08 15:11:13 ... Most recent comment 2020-06-09 10:19:27
Rigid Supports

​Hello Mitra,

I know the old masters used  solid poplar and oak wood panels that were dried heavily in order to avoid warping and having the acids rise to the surface.  Obviously they also sealed them in order to have extra layers of protection.

Now a days with ovens that dry the wood, and things like plywood and mdf like  wood,  im curious to know if we have to worry about the acids rising to the surface and about the warping? Technically plywood warps less and mdf if sealed doesnt absorb moisture and shouldnt warp.  I dont know about the acids in the mdf and if they are problem.

Are plywood and mdf panels suitable for painting? Should artists just stick to solid wood? Are MDF boards and plywoods even archival? 


Synthetic Papers for Painting Substrates

Question asked 2020-05-29 15:25:31 ... Most recent comment 2020-06-03 17:27:22
Flexible Supports Grounds / Priming Oil Paint Matting, Framing, and Glazing Rigid Supports Sizes and Adhesives

Hi all,

My surface of choice is an ACM panel (lightly sanded and with an acrylic clear gesso applied). However they can be a bit expensive for more experimental or practice works. Or when a painting goes wrong!

So I have been looking into synthetic papers and after looking at a selection of samples I tried a small sheet of PICOFILM from SIHL. It worked so well I ordered some larger sheets to do a painting on, which came out really well. It's basically white PET-G with a very matt primer which gives the the very slightly coarse feel of paper.

Here are the details of the surface from their technical sheets:

PICOFILM P-125 M2 matt

Synthetic matt paper. Ideal for waterproof and tear-resistant loop-locks, hang tags, weatherproof hiking maps, race numbers, menus, hard-wearing handbooks, booklets and brochures. 

PICOFILM P-125 M2 is a white polyester film coated both sides with a matt primer. It is weather-resistant, chemical-resistant, temperature-resistant and dimensionally stable. It can be cut, punched, perforated and drilled without issue. It’s also suitable for hot foil stamping and laser cutting. 

The high-quality coated film surfaces offer optimized feed properties and printing results. The slightly coarse surface, which is specially developed for laser printing, has an anti-static effect and prevents double-feeding. Suitable for monochrome and fullcolour laser printing, and for UV flexo and conventional offset pre-printing with oxidative drying inks. With fast ink drying, ideal ink adhesion and toner fusing. Can be stamped easily and lettered manually. 

High tear resistance
Excellent ink adhesion and toner fusing

The surface is very matt, even more than a white polyester coil coated matt ACM panel. It has a slightly rough feeling like paper or ultra fine sandpaper. The primer can be easily scratched off with a fingernail, but otherwise is a perfectly level and even surface (more than can be achieved using acrylic paint)

I applied two coats of clear gesso and it didn't buckle or warp as even heavyweight paper does. When I tested water paints and oil paints on an untreated surface I saw some absorbtion but absolutely no warping or cockling.

The oil paints developed the familiar oil ring of an absorbent surface after some hours and the paints did dry quicker (but still took several days or longer to dry).

Adhering the paper to a board is a bit tricky because both the surfaces of paper and ACM panel are plastic I've found Golden Acrylic Gel and PVA glue do not seem to dry (even though there seems a bond). They still appear wet when pulled apart after several days.

I'm currently testing out some Pressure Sensitive Adhesives (spray, tape and pot based) but I am seeing some distortion of the thin paper (bubbling underneath) from the glues - possibly from the solvents, so going to try leaving them to dry more thoroughly before bonding. There are also thicker grades of PICOFILM available, but don't know how much that would help.

I tested out sticking the PICOFILM paper to a paper mountboard from Daler Rowney with PVA glue and the bond was so strong then when I tried to remove the PICOFILM it was pulling off layers of the mountboard until the PICOFILM inself ripped when I used great force.

So, my concerns are:

If the primer is mechanically stable enough to be used with oil paints without some additional gesso or primer.

Is the primer going to react negatively with the oil paint.

Can I adhere it to a rigid surface without visible bubbles from the glue appearing and getting it to form a suitable bond.

I like the surface and it works out very cheap compared to thick normal papers (which still need stretching), or canvas/linen.

I have been in touch with SIHL who produce the paper and they've not heard of anyone using it with oil paints before. They are keen to know my experiences with using it and have sent me more samples.

I wondered if you had any thoughts, or any experience with artwork on these new synthetic substrates?

Thank you for your help,

Nontraditional use of egg tempura

Question asked 2020-04-03 12:26:51 ... Most recent comment 2020-05-18 01:07:43
Egg Tempera

​I have a few questions. I'm a painter/printmaker and have enjoyed making very juicy, loose oil paintings and monotypes for a long time. I've always been captivated by the color quality of egg tempura. I bought a set of Sennelier egg tempura tubes and egg tempura medium. I'm thoroughly enjoying painting loose and relatively thick layers, which I realize is totally nontraditional for this medium. Do you have any advice how to best protect my finished pieces? What are the disadvanages to painting thick layers instead of multiple thin layers? What are the disadvantages of not applying any protective layer over the egg tempura paint? Basically I just want to keep experimenting in my own juciy, expressive way and be able to protect the paintings.

Methylcellulose/oil emulsion paint

Question asked 2020-05-10 08:49:02 ... Most recent comment 2020-05-10 13:45:55
Oil Paint Industrial and Non-Traditional Products

I've come across recipes that claim methylcellulose gel (made from powdered MC mixed with water and allowed to gel) can be used as an emulsifier, much like egg yolk, and added to oil paints to make them faster-drying and (up to a point) water-miscible. Is this as archivally-sound as using egg yolk? Are there any special precautions that need to be taken?​

Titanium dioxide permanence.

Question asked 2020-05-04 02:27:28 ... Most recent comment 2020-05-08 22:38:17
Pigments Oil Paint Art Conservation Topics

​Considering that titanium (oil paint) forms a weaker film than lead, and it's been in use for around 100 years, is anyone aware of any conservation issues arising from its use yet?

Also, I'm interested in mitigating the weakness of titanium with the addition of lead. Does anyone know if there have been any stress tests done with different proportions of lead mixed with titaniun?

Ron Francis

Acrylic Primer with Sand OK under oil paint?

Question asked 2020-05-01 04:18:49 ... Most recent comment 2020-05-01 19:43:03

​Dear MITRA people

I have some acrylic primed artist grade polyester canvas that I find objectionable to use because it has very little texture or tooth (unlike another brand I tried that was lovely to use). The surface is rather slick. I have tried experimenting with home made grounds made of acrylic primer plus marble dust or calcite as well as acrylic primer with pumice but the first 2 gave too little tooth and the last one (because we can't get ultra fine pumice in Australia) was far too coarse. I recently found some Liquitex brand "Natural Sand" acrylic gel, and put a thin coat of it over the original priming on the polyester canvas. It definitely gave a good degree of tooth. Is it relatively sound to paint over this in oils? I will be adhering the canvas to a board first as I always prefer a rigid support. 

Egg Tempera Cracking/Crazing

Question asked 2020-04-28 17:41:55 ... Most recent comment 2020-04-30 18:37:45
Egg Tempera

Background: I have a panel with many layers of egg tempera on it, and I put a "nourishing coat" over some areas. After it dried the surface developed a large number of tiny pits and cracks. My emulsion, which I used for the nourishing coat, is 1:1 egg yolk and white wine. The nourishing coat was ​straight emulsion, and I should have diluted it with more wine (1:2 egg yolk to wine). I assume that the yolk created too much surface tension and pulled at the paint layers, creating the pits and cracks.

Question: is there any way that I can fix this problem? I am many months into this painting and it would be devastating to lose it at this point.

My Current Actions: I tried painting a diluted nourishing coat over the affected areas to no avail. I then tried brushing straight wine over the affected areas, many, many layers, which seemed to work. I assume because I was breaking some of the surface tension of the rich emulsion (1:1 wine to yolk). Most of the pits and cracks closed up, but then I let it dry completely and they opened slightly again. The end result is better than what it was, but it still isn't where I want it to be.


Mixing a Drying Oil with an Alkyd Medium

Question asked 2020-03-30 09:54:04 ... Most recent comment 2020-04-17 20:57:01
Alkyd Drying Oils Oil Paint Paint Additives Paint Mediums

I have seen where some manufacturers do give the OK to mixing OMS with their Alkyd Mediums. What if one wished to add a Drying Oil such as Linseed or Walnut oil mixed with an Alkyd Medium to moderate the drying time? Of course, being sure to follow Fat over Lean rules by adding the same amount or slightly more drying oil in the mixture to each subsequent layer.

  • If it is OK to do so, is there a safe maximum amount of drying oil that could be added to most alkyd mediums?
  • For the moderators who also work for a specific brand of art materials, what would be a safe amount of drying oil to add to your various Alkyd mediums?
  • Would it be best to stick to a specific ratio mixture of the drying oil with a chosen Alkyd medium to be used throughout the painting, or should slightly more oil be added to the mixture for each new layer, not exceeding any recommended maximum drying oil to Alkyd ratio?
  • If the answer is no to mixing drying oils with Alkyd mediums, what is the reason for not doing so?

I am looking for a general guideline if that is possible to give a maximum ratio of oil to Alkyd medium that would generally be safe to use with most Alkyd mediums, even if it was a very low percentage. It doesn't take much Walnut oil for example to slow the drying rate quite a bit with some paints. I realize that all Alkyd mediums are not the same and that some makers might recommend not adding any drying oil to their Alkyd mediums, so it should not be done with those products. Additionally, a maximum recommended amount of medium for one brand may not work for another brand that doesn't give any ratio recommendations, which means an all-inclusive answer may be impossible to provide, but I was very interested in seeing what you folks had to say about this. 

Linen to panel adhesive

Question asked 2020-03-30 14:05:38 ... Most recent comment 2020-03-30 20:33:37
Oil Paint
A collector sent me a photo of a painting he purchased from me that had huge ripples and sagging. It was a commercial linen canvas on stretcher bars. I will fix it for him and intend to glue it on a hard panel; what is the best adhesive to use to adhere to a composite material panel?

How to make oil paint very matte

Question asked 2020-03-22 00:41:05 ... Most recent comment 2020-03-26 20:14:53
Oil Paint


I'd like to have passages in an oil painting that resemble poster paints in their very matte sheen. 

Can you recommend some ways to make oil paint extra matte? 

I've had a little luck with additional OMS/ Turps, absorbing oil from cardboard, and the additon of cold wax, but wondered if there were other/ strong 'matting agents' for oil paint. I think Gamblin makes a Matte Oil paint (how?) I have yet to find in stores...



Source for lead primer

Question asked 2020-03-11 05:16:02 ... Most recent comment 2020-03-21 22:14:11
Grounds / Priming

​Can anyone tell me a source for lead primer made without marble dust?

resuming work on older oil paintings

Question asked 2020-03-11 01:57:35 ... Most recent comment 2020-03-17 20:16:10
Oil Paint

​Dear MITRA,

I have searched the MITRA forum and resources, and while I have read similar questions to mine, I am not locating an answer to my exact inquiry.

I am about to resume work on a large format oil on linen diptych after I had to set them aside for a few years. I recently received funding to complete the full project for an upcoming solo exhibition, so I look forward to completing these initial works. I want to use the soundest methods possible to finish these canvases, and would like to know if my approach sounds like the best route to take.

I am using oil paints made with walnut oil, and initially used a solvent-based alkyd medium cut 50/50 with OMS for my underpainting, then a walnut/alkyd medium with increasingly less OMS for subsequent fatter layers. I never adulterate more than 20% as I alter the fat-to-lean ratio. On large parts of each canvas, the underpainting and canvas tooth are still visible, while other areas are comprised of a second or third layer as I had developed them to near completion.

Here is my suggested approach to complete the works, along with my questions about each potential step:

1. Cleaning – I plan to give both of the canvases a gentle rub with OMS to get rid of any potential dirt or fingerprints, etc, before resuming painting.

2. Sanding? –

(a) do I need to gently abrade the areas where I got as far as a second or third layer to break the seal of the paint and insure best adhesion? Or only sand where any fatter third layers look glossy? I presume that I wouldn't need to sand the underpainting areas that still feature good canvas tooth.

(b) If sanding is recommended, since I don't want to alter my composition (so pentimenti isn't a concern), would I only need to break/scuff the surface, rather than sanding down to the underpainting? Would wet sanding with a little OMS or distilled water be advised for safety? (I know to wear an appropriate mask and dispose of the pigment dust responsibly, etc.)

(c) I also wondered if I'd only need to sand where the final highlight and darkest shadow layers are going, but that sounds potentially more complicated or confusing and would limit my method of execution.

3. Limiting layers – for best adhesion, in this case should I limit myself to a certain number of paint layers wherever possible? I typically use an indirect painting method to create a fairly naturalistic end result by employing glazes on top of a wet-in-wet or wet-on-dry base. As I recall, limiting yourself to three layers including the underpainting when possible is a good practice for longevity anyway…? The number of layers I would need to employ would also be affected by how much (if any) sanding you would recommend, because I will essentially have to redo anything I sand.

I welcome your input on the best way to proceed. While I know that resuming work on canvases whose layers are this closed off isn't necessarily the best case scenario, starting over does not appeal to me from the standpoints of both time and expense. I frequently see Old Master examples wherein the artist spent years completing the works or resumed painting after a few years, so I suppose there are worse studio practices. 

Thank you so much for your time and expertise!

Removing mold from pastel sticks

Question asked 2020-03-13 08:29:10 ... Most recent comment 2020-03-14 12:28:08

How do I systematically remove/treat mold or mildew on my affected pastel sticks in a relatively safe manner in my studio  (in humid Louisiana and try to prevent its return? 

Mold/mildew on pastel sticks

Question asked 2020-03-11 22:03:19 ... Most recent comment 2020-03-11 23:52:49

I recently found numerous white small tuffs of mildew or mold growing on my very dark pastels (dark brown/black/blue), with two pastel companies' brands being most affected. My studio is in the gulf South, an area of high humidity and I run the air conditioner when It is warm and I am at the studio (not all the time). I need to figure out why it seems that only the darks are getting this growth it the possibly the preservative used, why mostly these two companies, why just the darkest darks, and most importantly, how do I systematically tackle the systematic cleaning of the pastels  in a relatively safe manner. I can send images, if that is possible.

number of pigments in an admixture?

Question asked 2020-03-11 03:33:04 ... Most recent comment 2020-03-11 17:19:29
Oil Paint Pigments

​Dear MITRA,

I've always favored a fairly limited oil palette, preferring to create my own admixtures rather than buy every tube of brown, green, or flesh tint. Recently I have expanded my palette to include some natural earth colors as I have begun to focus on using leaner *pigments* under fatter ones in addition to following the fat-over-lean rule regarding the amount of oil medium added.

Is there a limit to how many pigments are a preferable maximum in any given admixture? Does it complicate the chemistry too much to blend several pigments to get just the right color? Is there any rule about mixing natural pigments with synthetic ones?

Many thanks for your help!

Using Pigment Markers on Acrylic Gesso

Question asked 2020-03-11 10:04:42 ... Most recent comment 2020-03-11 16:43:00
Acrylic Art Conservation Topics Grounds / Priming Solvents and Thinners Varnishes

Hi all,

I would like to explore using W&N Pigment Markers which seem to use a good selection of commonly used ATSM I/II pigments but are available in a marker form. I already have a few of their water colour markers which I like, but there are many more colour choices in their Pigment Marker range.

However they are ethanol based and I understand that alcohol/ethanol would act as a solvent on acrylic gesso? I know they can be used on Yupo and other alcohol resistant plastics, but I am looking to add clear Gesso which contains silicia make a more toothy suface. A non-absorbant, more pastel ground like surface.

Considering that with the markers I would be making rubbing motions I'm not sure what I could put over the Gesso to protect it from the alcohol. Are there any varnishes that are not soluable in alcohol but will resist a rubbing motion?

The only thing I could think of was a layer of water based polyurethane (but I am concerned about yellowing).

Any ideas or suggestions?


Lead primers

Question asked 2020-03-11 05:12:39 ... Most recent comment 2020-03-11 05:07:00
Grounds / Priming

​Can anyone point me to a source for a lead primer made without marble dust (calcium carbonate), either a maker or a seller?

resuming work on older oil paintings

Question asked 2020-03-11 00:53:41 ... Most recent comment 2020-03-11 02:00:40

​Dear MITRA, 

I have looked through other posts and while similar questions have been asked, I do not see my exact question.

I am about to resume work on a large format oil on linen diptych after I had to set the works aside for a few years. I started them in 2013, and last worked on them in 2015. Now I have funding to complete the project for an upcoming solo show, and want to resume work using the soundest methods possible. I don't want to cPlease let me know if 

1. Cleaning -- with OMS then let dry

Glue emulsion

Question asked 2020-02-21 22:01:21 ... Most recent comment 2020-03-10 16:57:51
Egg Tempera Oil Paint

​I am interested in experimenting with glue emulsion and oil paints.  My understanding of what the emulsion paint is capable of doing may not necessarily be in line with what is sound painting practices.

 I have a recipe from Patrick Betadier's technique mixte I will probably follow to make the emulsion.  The ingredients are methil cellulose, linseed and stand oil, turps and dammar varnish and water.

My question is more in terms of using the emulsion within the oil layers and whether that's possible, as the emulsion paint would essentially be neutral in the system of fat/lean.

So the painting would be built following fat over lean in oil, however the emulsion + pigment paint would be introduced and sandwitched between layers of oils.  My interest would be more limited to painting final details, where I would apply a thin colored oil glaze and work into it with the emulsion paint.

I am wondering if glue emulsions are indeed fat/lean neutral and if now, what are their limitations.

Final Varnish on an Encaustic

Question asked 2016-11-10 19:00:28 ... Most recent comment 2020-03-09 13:33:15
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.

Micronized Zinc Oxide

Question asked 2020-03-07 10:39:09 ... Most recent comment 2020-03-09 11:21:09
Art Conservation Topics Oil Paint Pigments Scientific Analysis Varnishes

​Hi all,

I've been reading about how micronized (or nano-particle sized) Zinc Oxide is used in Suncream to protect from UV light. As I understand it the very small size particles also make the zinc oxide more transparent.

Would this form of Zinc oxide used in a varnish (perhaps as a matting agent) help with UV protection? Would it break down being metal based?

Also, I wonder if this form of Zinc oxide added to oil paint would help contribute metal ions to the oil firms, but without the brittleness it can cause?


A bit of rust in a pen for ink

Question asked 2020-02-26 06:29:36 ... Most recent comment 2020-03-05 11:19:35
Ink Pen

​Hello dear people from Mitra.

Recently i began a ink drawing that i am really happy with, but last night i realised that my pen for ink had started to rust a bit...

The reason i didnt realise this before was because the pen was working great, and it was not clearly visible. I realised this when i had put it in destiled water and it was a bit yellowish, then i looked inside the pen and saw a little bits of rust on it...

I really care for my materials and especcialy my art, but i guess that this stuff happens.


I hope that artwork will remain as it is, but i wanted to ask to be sure? 

Thank you 

Kind regards

Marko K

Custom Table Pads

Question asked 2020-02-27 03:51:47 ... Most recent comment 2020-02-27 19:44:23
Other Drawing Materials

What kind of tables you are using for drawing, do u have any requirment of of <a href="">table pads</a> ?​

Fixative or varnish for oil & wax based pencils on paper

Question asked 2020-02-07 08:24:30 ... Most recent comment 2020-02-27 19:41:16
Pencil Varnishes

​Hi! I'm trying to find a suitable fixative to protect my drawings made with oil- and wax-based colour pencil on 300gsm Arches hot pressed watercolour paper. I only need to protect against accidental smudging and UV protection is not my concern (I only use ASTM 6901 grade pencils).

I've tried a Schmincke universal fixative so far (I live in Germany so that was a natural choice) and it gives good smudge protection and almost no colour change. However it lists "polyvinyl resin" as its main binder which is ambiguous, and Schmincke have officially declined to disclose any further details on the type of resin they use. From what the industry uses, I assume it must be polyvinyl acetate which is known to slowly disintegrate, releasing acetic acid. Assuming that fixative indeed uses polyvinyl acetate, would you consider it archival enough to be used with paper and colour pencils?

My second question is: what's the best recommended smudge protection fixative/varnish for oil/wax-based coloured pencil works on paper? I did a fair amount of googling but resources related to coloured pencils protection are virtually nonexistent (also no vendor in Europe, to my best knowledge, market any varnishes/fixatives as specifically suitable for coloured pencils).

Thank you very much for any assistance you'd be able to provide with this topic!

Technical queries (isolation varnish + final varnish) in the Mixed Technique (ET + oil)

Question asked 2020-02-21 14:07:42 ... Most recent comment 2020-02-21 17:53:00
Varnishes Egg Tempera


thanks a lot for all your comments and suggestions. 

I know that it is not recommended to varnish or coat an egg tempera painting. In my case I use ET for the underpainting because it allows me a very precise drawing and it dries really fast. The problems come when I add oil. The base is so terribly absorbent that I can't manipulate the first oil layer. Soon after I start with oil paint doesn't flow normally, which doesn't allow me to keep going.

I have done many tests and when I isolate ET with Paraloid B72 or an oil medium (1 part stand oil + 2 parts turpentine, for example) the brushability improves considerably. The base is still absorbent, but it allows me to work on it.

Is there a better alternative to an isolating varnish? I am concerned about the preservation of my paintings, but this issue just doesn't let me keep painting.It may be a silly question, but... would it be more reasonable to apply an isolating coat with an emulsion medium? I mean, mixing an oil medium with an ET medium. For example, the medium I am using to grind my ET colours with 1 part stand oil + 1 or 2 parts turpentine. Any other suggestion maybe?

Thanks again.


isolating coat over egg tempera grisaille

Question asked 2020-02-18 15:25:41 ... Most recent comment 2020-02-19 09:00:07
Varnishes Egg Tempera


I have serious doubts about what kind of isolating coat would be most appropriate for me.

I'm looking for a varnish to seal egg tempera that is also compatible with a final varnish, which will go over the last layer of oil.

As the isolating coat penetrates over the tempera, it becomes part of it. I would like to know, according to your criteria, which combination of varnishes I could use.

Here is the structure of my paintings:

Egg tempera underpainting in grey values. This layer is extremely matt, due to the fact that I thin the ET with a lot of water. Then I apply combined oil glazes and intensify the lights with white tempera grassa (highlights). Finally I finish the painting with oil paint.

I have tried Paraloid B72 (15%) by Kremer and it is completely transparent. The problem is the brushability. So I only manage to apply it in small areas. It is impossible to give a uniform layer to the whole painting and I prefer not to spray it.

I have tried Gamvar (Gamblin) as well. The brushability is great, kind of gelatinous. But even after drying it is still a bit yellowish or dark. And I am not sure if it is compatible with ET.

One last question. In the following link it says that if adding UV light stabilizers to the varnish it should be added to both layers (isolating coat and final varnish), what do you think?

Thanks a lot in advance and best regards.


Using Gatorfoam board as a rigid support for watercolor paper

Question asked 2020-02-18 13:41:28 ... Most recent comment 2020-02-18 15:29:06
Rigid Supports Watercolor

​I have heard watercolor artists and seen utube videos by watercolor artists promoting adhering watercolor paper to gatorfoam board as a permanent, rigid support.  The watercolor painting is varnished when complete.  

I was looking at using the gatorfoam board in this way for a large (36" x 48") watercolor painting I plan to do.  While the artists mentioned seem to believe the gatorboard is acid free and archival, I'm concerned that it may not be.  It is light weight, strong and very rigid which make it appealing as a support but I'm concerned about the long-term effect on the watercolor paper and painting.  Please give me your opinion.  Thank you!

Low Cholesterol Eggs

Question asked 2020-02-14 14:23:04 ... Most recent comment 2020-02-14 14:17:00
Egg Tempera

I have a student working with "lower cholesterol" eggs, marketed as having "25% less saturated fat", to make egg tempera paint. She's having a hard time geting her tempering correct.  The obvious answer is that there isn't enough egg oil in the yolk for her to make a good paint film - yes?  Any other considerations regarding working with low cholesterol eggs?  Needless to say, I'll encourage her to switch brands.

Koo Schadler

question on spray lacquer

Question asked 2020-02-11 21:31:19 ... Most recent comment 2020-02-13 14:02:43
Industrial and Non-Traditional Products

​I do multi-media work on Ampersand's panels and use multiple coats of Golden's archival spray varnish as a protective coating. Recently, out of curiosity, I lightly sanded Golden's gloss varnish and top coated it with 2 coats of nitrocellulose lacquer. To  my surprize, nothing terrible happened, at least visually at this current moment in time. 

I understand that lacquers are a no-no do to their propensity to crack and amber with time. But, could they be used on top of an archival varnish solely for the purpose of aesthetic reasons? I have always been told that brittle products can't be used on softer ones, but I have been asking myself: so what if the nitrocellulose lacquer cracks and slightly ambers in 100 years? (A person I spoke to from a lacquer manufacturer told me that today's Nitrocellulose lacquers are not the same as the ones first developed), that they take a much longer time to crack and significantly yellow).  As long as Golden's archival varnish is the actual protective layer (used as the permanent layer), couldn't two thin coats of spray lacquer be removed by physically sanding it off? And since lacquers re-wet themselves, couldn't the picture just be recoated with new lacquer, or a new invention(hopefully after a 100 years) that isn't so plastic looking?

Grateful for any thoughts,


Oil Painting on unprepared hardboard (Masonite)

Question asked 2020-02-07 15:28:17 ... Most recent comment 2020-02-07 15:54:04
Oil Paint

​A customer of mine—I run an art store—came in saying he painted an oil painting 20 years ago "on Masonite" with no surface preparation. He says it looks the same, but is wondering if he can do anything to help its longevity. (Aside from cleaning and varnishing.) Any advice since the substrate was not sealed? What is he up against?

Painting on wood

Question asked 2020-02-06 10:57:55 ... Most recent comment 2020-02-06 15:54:19
Acrylic Grounds / Priming Oil Paint Rigid Supports Sizes and Adhesives Watercolor

​1. When painting with acrylic followed by oils on wood panel 

(specifically birch veneer) is it best to seal the wood first with acrylic primer such as kilz followed by gesso?

2. When stretching canvas over wood panel is it best to prime the wood panel first, then stretch followed by gesso?

3. If glueing canvas to panel, prime first? What glue is best to adhere canvas to panel? 

Painting on wood

Question asked 2020-02-06 10:50:39 ... Most recent comment 2020-02-06 10:41:00
Acrylic Drying Oils Gouache Flexible Supports Grounds / Priming

I have always painted with acrylic, often followed by oil on canvas. 

Am exploring painting on wood panels, specifically birch veneer.


1. Should I seal the wood first with primer (kilz) followed by 


2. If I glue canvas to wood panel before painting what glue is

best and do I still prime the wood first followed by gesso on canvas?

3. What substance do you recommend for gluing paper onto

wood panel? 

Thank you so much for your help!

Fixitive before Egg Tempera?

Question asked 2020-01-30 11:53:47 ... Most recent comment 2020-01-31 09:19:03
Egg Tempera

​I am very new to egg tempera painting. I have completed a drawing in pencil on a gesso panel. I am wondering a couple things:

1. Is it necessary to india ink over the pencil?

2. If I dont do an india ink underdrawing on top of the pencil, will the pencil mix with the egg tempera paint and make it muddy?

3. If I spray a fixitive (like a krylon drawing fixative) over the drawing will it negatively affect the tempera? 

4. Has anyone found that using india ink over pencil helps to seal the pencil and prevent it from mixing with the tempera?

Substrate for marbling and oil

Question asked 2020-01-14 22:34:27 ... Most recent comment 2020-01-31 07:48:35
Grounds / Priming Gouache

​hi there, I'm trying to make large 6 x 8ft marbleized surfaces that I will then paint with oil on top. I'm having trouble finding canvas that is white enough and unprimed at that scale. My options as I understand them are,:

Apply alum to paper, marble the paper, adhere to canvas, apply matte medium , paint oil on top

Apply alum to 100% cotton bed sheet, marbleizing,  stretch on its own or over canvas, apply matte medium, oil paint on top

Or apply golden absorbent ground to primed surface, apply alum,  marbleize, apply matte medium, oil paint over

Or? Any other ideas? Will alum have any negative effects? Can paper be adhered to canvas and then painted over? Bed sheets with high thread count? What are the most durable options here? Thanks!!! 

Black oil - is it beneficial?

Question asked 2020-01-15 16:52:10 ... Most recent comment 2020-01-28 16:56:38
Oil Paint Drying Oils


I'd like to ask about black oil (leaded oil). I found somewhat contradicting informations about it.

Natural Pigments sells "Dark drying oil (Black oil)" and the description says:

Dark Drying Oil or black oil is a fast drying oil made by heating linseed oil with lead oxide (litharge) and used in historical oil painting. The lead (metal basis) content of our dark drying oil is about 3% by weight.


Black oil can improve the handling and drying of oils and can be used in recipes to make megilp, Maroger and Roberson's mediums and traditional oil varnishes, such as copal.

I'm not interested in Maroger and Roberson mediums, or traditional oil varnishes, but the statement "Black oil can improve the handling and drying of oils" sounds intereseting to me. As far as I know certain lead compounds speed up drying of the paint film and/or increase its flexibility and durability. Thus, it would seem to be useful medium.

However in MITRA pdf article "Myths, FAQs, and Common Misconceptions", there is this statement in the last chapter about Maroger mediums on page no. 11: "Dr. MarionMecklenberg of the Smithsonian Institute’s Museum Conservation Institute,however, has shown that paint films containing even small amounts of leaded oilare substantially weaker than those containing only cold pressed linseed oil."

Of course I realize that the actual amount of black oil in medium/binder can have varying effect. But generally - how is it with black oil? Can it provide any advantages, e.g. better balanced through drying of paint film and increased durability, or not?

"Beading up" or reticulation of oil paint

Question asked 2020-01-24 10:19:42 ... Most recent comment 2020-01-24 19:38:24
Grounds / Priming Oil Paint Other

​Hello Everyone,

Im currenty grinding my own colors and starting to paint with them. But im running across a problem and thats the beading up of certain colors.  

After trying to find answers online , it seems that this occurs because  my surface has a  lower surface energy than the paint.  If this is correct it seems that I have two options, I either have to change the surface or change the paint.  

Would spraying alcohol on my surface work? Or thinly oiling out and letting it dry? What can I put on the surface that would make the paint stick better?  Can I add something to my paint?  

P.s. I cant sand the surface since i did an underpainting and i dont want to damage it. 

Best Regards,


Support for Large Scale Egg Tempera Painting

Question asked 2020-01-16 12:15:18 ... Most recent comment 2020-01-22 11:19:35
Rigid Supports


I reviewed prior questions and comments in the "rigid support" forum before posing my question. I've been using 1/8" hardboard, cradled approximately every 12" with kiln-dried douglas fir 1" x 2" stripping. This seems to work fine. I do apply 8 coats of traditional gesso front and back, finishing with one coat of alkyd paint on rear per Koo Schadler's instructions.

My main issue is weight. On a 4' x 8' panel this becomes very heavy. I need the help of a friend to move it at all.

Is there a lighter weight material that I could safely try? I wrote to Simon Liu but he says his panels are not safe for traditional gesso.

What about coroplast, or an archival foamcore type material?  I could still cradle it with wooden strips for rigidity and would be willing to glue a muslim layer on. Any ideas for lighter weight materials?

An advantage of my system is, of course, that it is dirt cheap but i would be willing to pay quite a bit more for a lighter weight solution.

Two other issues:

1. It is almost gospel that we are to use untempered (standard) hardboard, but I've heard from manufacturers that the amount of oil or resin in modern hardboard is miniscule and actually adds to the integrity of the board, as untempered does tend to chip more at the edges. Perhaps at this point it is just myth that the oil will migrate through to the gesso and affect the painting? For a long time I could not source untempered hardboard in California except by ordering 100 sheets shipped by freight. But now I can buy it locally but I'm wondering if tempered may actually be better?

2. The logic behind applying equal number of coats of gesso, front and back is to equalize the forces in order to prevent warpage. However, the hardboard that is available to me has a "screen back" so it absorbs more gesso. Plus the rear has cradling which also affects the amount of gesso, so is perhaps appling equal coats no longer necessary or, in fact, should I be quantifying the amount of gesso applied either by weight or volume to ensure that the amount is equal on front and rear?

That's it! Thanks so much. It is comfortaing and amazing to have this in-depth MITRA forum available to us artists.

Lora Arbrador

Loom sized linen

Question asked 2020-01-20 00:38:27 ... Most recent comment 2020-01-20 15:41:26

What is the standard size used in​ Unprimed linen and is it advisable to remove it with gentle washing before users sizing and priming?


Soy oil for printing

Question asked 2020-01-08 11:20:39 ... Most recent comment 2020-01-17 17:45:49
Drying Oils

​Hi, my collegue from the Printing Departement on my academy, recently switched to soy-based printing inks. These are made watersoluble, so we need no mineral spirits for cleaning anymore.
His complaint, however, is that the inks dry very slowly, as in at least a week, or so. This does not work, at an art academy. So he asked me for advice, but I do not know of soy oil being used as oil for paints or inks. Is it even a drying oil?

Does anyone here know what to do? Is there a way to let these inks dry faster (cobalt dryer?) Or is it 'dead on arrival' and should we use a different inkt?

I hope you can help us with this, thanks in advance.

How to store egg tempera paintings

Question asked 2019-12-12 23:56:18 ... Most recent comment 2020-01-15 12:13:14
Egg Tempera


I'm aware that the optimal way to store an egg tempera (or any painting) is to place it upright in a rack. None of the paint-bearing areas of the painting should be touching the slats of the rack. Two questions:

1. I would feel more comfortable covering it with some loose plastic or something in case of leaks. I understand that as long as the painitng is upright water will bead off of it. But still I would feel better if there was some sort of barrier.

2. Living in an apartment and not having a rack for paintings, plus some of my ET's are as big as 4' x *8 I'm trying to figure out how to safely store them. I used to wrap them in cloths such as sheeting and then wrap with plastic. I would like to be able to store them flat. 

Any ideas?

Thanks much, Lora Arbrador

Gamsol v/s Turpentine: Safety + Surface Quality

Question asked 2020-01-06 22:56:08 ... Most recent comment 2020-01-14 09:41:42

I was recently discussing ways to mitigate surface irregularities during the painting process, as opposed to varnishing, with a specialty paint merchant. They recommended reducing the amount solvent in my medium and using a less bodied oil like walnut for flow, which seems like good advice. However, they also recommended switching from Gamsol to double rectified Pine Turpentine, which I have questions about.

I currently use a 50/50 mix of Gamol and Linseed oil and my paintings aren't too many layers.

I know Turpentine and Gamsol have a different feel under the brush, but would turpentine actually help to create a more mat, uniform surface? 

The merchant disagreed with me about Gamol being a less toxic solvent, which I've always been told. If I'm understanding the MITRA Resources pdf on solvents (word in parenthesis my own)- "Aromatic hydrocarbons (like turpentine) tend to evaporate more slowly and are more toxic than aliphatic hydrocarbons (like Gamsol)". Can you confirm that Gamsol is indeed safer?

Thanks in advance for any thoughts!

Diluting retouch varnish

Question asked 2019-11-25 17:42:53 ... Most recent comment 2020-01-11 22:50:11


Can retouch varnish be diluted to make it less shiny, and if so, with what?

Thank you!

Beading of oil or varnish on a dried oil paint surface

Question asked 2020-01-06 18:38:12 ... Most recent comment 2020-01-07 17:34:24
Varnishes Oil Paint

 when trying to oil out dull areas, glaze or put a varnish over my paintings in some areas the medium, varnish or thinned paint just beads up. It is difficult to cover with anything except straight paint. I use Williamsburg and Winsdor and Newton paints lightly thinned with linseed oil on a lead grounded high quality linen canvas. I've been told to use toluene in the varnish or medium. 

Cooking oil as a medium

Question asked 2019-06-21 08:50:41 ... Most recent comment 2020-01-06 18:40:45
Oil Paint Paint Mediums

​On various art forums people often ask about using grocery store cooking/salad oils, such as walnut oil, as a painting medium. They are usually trying to save a bit of money. It seems like a false economy that could likely cause probelms down the road and negate hours of work put into the paitning process just to save a few dollars on materials.  I'm aware that there is an obvious problem with some grocery store oils containing added anti-oxidents to maintain freshness.  Are there other issues, related to the differences in how edible oils are processed as opposed artist grade oils, that can cause problems in the quaity of paint film formed?


Question asked 2020-01-06 11:00:15 ... Most recent comment 2020-01-06 18:22:26
Egg Tempera Environment


I've had several people ask me about mold issues on egg tempera paintings.  I understand that the porous, high PVC surface of an unvarnished tempera is more prone to mold (since moisture more readily enters in).  My questions are:

- How detrimental is mold on top of a paint surfaces (both on other mediums generally, and egg tempera specifically)?  

- Aside from taking the work to a professional conservator to clean, what can a person do?  I've known people to wipe the surface with alcohol, which seems to work well in removing the mold; however I'm concerned it may compromise the paint film if applied to liberally (abrade with applicaiton, or sink in and lead to embrittlement).  What about using Phenol?

- A person recently wrote me with this question and wondered how consequential mold was for past painters, given that they did not have climate controlled spaces.  Do you know if mold was  historically a big problem? 

Koo Schadler

Gesso Ratios

Question asked 2019-12-27 09:21:36 ... Most recent comment 2019-12-28 13:03:39
Grounds / Priming

Hello All,

In making gesso, my experience is to first establish a ratio of glue to water, my preference being 1 pt. glue to 16 pts. water (1:16).  While I've always believed there is some variability in that ratio (my guesstimate, from 1:12 to 1:20), a past MITRA question clarified that, given the complexity of glue, the variability can be greater than that (i.e. one paint company recommends a 1:5 ratio) - it all depends on glue factors. 

Anyhow, the second relevant gesso ratio is glue water to chalk or gypsum (whiting).  The most common ratio I see (and use) is 1 pt. Glue Water: 1.5 pts. Whiting.  This generally yields a gesso with the consistency of light cream or whole milk, ideal for applying gesso.  Too thick a gesso is more apt to crack.  

The Mt. Athos monk with whom I've conversed in the past is asking another question, relative to the above.  His gesso recipe, like mine (1 glue: 16 water + 1 glue water: 1.5 whiting) is yielding a gesso with a heavy cream or pudding consistency.  He is asking which is more relevant: staying with consistent ratios (even if it yields a thick gesso), or shooting for a gesso consistency of light cream (even if that means adding less whiting).  My gesso never yields a pudding-like gesso, so I'm puzzled why he's getting that.  Regardless, I would say consistency is more important - applying pudding-like gesso is not good.  But then again, gesso is essentially a high PVC paint, and if one too dramatically alters a paint's PVC, isn't that problematic?

I realize all this is complicated by variabilities in ingredients and measuring, environmental factors, etc.; and there is not a simple answer.  Nonetheless, I welcome general thoughts on the above, as well as a response to the specific question of which is more important: staying with consistent gesso ratios, or adjusting a ratio (perhaps dramatically) to yield a thinner gesso consistency.  


Koo Schadler

How to label the back side of an oil painting on canvas

Question asked 2019-12-11 23:35:33 ... Most recent comment 2019-12-16 00:40:31
Matting, Framing, and Glazing Oil Paint Flexible Supports

​Forgive me if this is answered elsewhere, but I'm looking for the best practices on labeling the back side of a painting on canvas on strainers. I'd like to include a professional description of the date, materials, and name/authentication of the work, etc. I've mostly only seen artists doing this in the past on panel by attaching a label, as in J. ALbers, but have heard adhering anything to the back of the piece will eventually disrupt the front tension- similar concerns about writing directly on the piece, and furthermore only labeling the stretchers seems to miss the mark. Perhaps on a dust cover, but this seems impractical on a larger piece... Any industry standards?

Many thanks,


Tempera grassa ground

Question asked 2019-11-03 17:58:26 ... Most recent comment 2019-12-10 11:09:23
Egg Tempera Grounds / Priming Oil Paint

​Dear MITRA administrator,

Which ground would you suggest for painting with egg-oil emulsion (tempera grassa)?

Ground should go on rigid support like wood panel. Emulsion ingradients are: linseed oil, egg and water in different ratios, nothing else.

Damir Pusic.

Watercolor surface identification

Question asked 2019-12-02 12:17:37 ... Most recent comment 2019-12-02 15:14:31

I have a watercolor piece by Albert Herter that I estimate to be from between 1894-1900 by the name of "Gift of Roses". I've been working on identifying it the past few days and have a few questions about watercolor surfaces from that period. When we looked at the back of the piece, I was suprised to see that it was on a kind of pressed board, and not paper as I thought. I did not remove it entirely from the frame to avoid damage, so it may be mounted, but the edges seem to be consistent, no paper glued, just painted directly onto this board.  I have pictures of the front and back for anyone that wants a look here

I'm a painter myself and am pretty certain it's not a print or crayon enlargement, but the surface has me questioning that.  Any help would be greatly appreciated. 

rheology of painting for glazing

Question asked 2019-11-30 20:46:58 ... Most recent comment 2019-12-02 12:40:11
Oil Paint

​Hello Mitra,

I always see people watering down there paints when they are going to make a glaze.  Many books talk about avoiding this bc if one goes extremely past the CPVC this will create an unstable film.  Is there a way to guage the making of paint for a glazing technique?  Is there some sort of general rule or rule of thumb that one should take into account when mixing paint for a glazing technique? 

Best Regards,


Repairing cracked masonite panel

Question asked 2019-11-27 21:52:02 ... Most recent comment 2019-11-30 13:12:39
Handling and Transportation

​A fellow artist and I collaborated on a piece together, in both acrylic and oil paint on a 36"x48" cradled Gessobord. I applied ArtResin to the piece which was curing perfectly in the storage area on the third floor of an art gallery. I went up to the painting on the third day and found a couple of deep cracks had appeared in the glossy ArtResin. Upon closer inspection I realized the cracks in the resin were a symptom of cracks in the masonite panel. Since it was in perfect condition two days prior, and it wasn't subject to wild fluctuations in temperature, I assume it fell and someone righted it, not realizing it has suffered. 

Now the other artist has been invited to ArtBasel and wants to take this piece. My question is; how can I repair the masonite so the end result is strong and also looks good enough should the piece sell?

I think I have figured out how to repair the resin by sanding it down and reapplying it, but any suggestions for that part are also appreciated.

Thanks in advance!

Studio safety of W & N Artisan thinner

Question asked 2019-11-25 17:41:40 ... Most recent comment 2019-11-28 14:46:31
Solvents and Thinners


recently read an article on this forum re water-miscible oils (2019-11-16) . This has rekindled my interest in using them again. I first started using W & N Artisan oils over 10 years ago, and off-and-on since. Problem is that if you use water as a thinner it evaporates almost instantaneously leaving a very short open-time. This was a big turn-off for me.

I have got their associated thinner (Artisan THINNER) which stays open for at least an hour and great stuff for altering an initial drawing/lay-in. (I only use it for the initial drawing). On specific questioning W & N advise to use a maximum dilution of 1:2 by volume ( 1x part oils : 2 x parts thinner). I usually use a bit less thinner than this. They stated that it was non-toxic also. (I realize that there can be a problem with this description in some cases) 

At the above ratio it does all the things I used to use turps for and, hopefully, a lot less toxic. Which is what I really want to know, ie., just how safe is this thinner?

I checked the MSDS for the product which states that: " This product has been certified by ACMI to carry the AP (Approved Product) seal, meaning this product bears no chronic or acute human health hazards". The Artisan literature also states exact same reference.

Specifically, under the heading 'Inhalation' it states no specific symptoms known. Also, not classified as a specific target organ toxicant after repeated exposure. Skin contact also had "No specific symptoms known".

The only caution was that it could cause irritation to eyes and mucous membranes; also that thermal decomposition.......may include harmful gases or vapors. However, is stable under normal ambient condions.

Initial boiling point >100 deg.C at 760mmHg.

In my home studio I have a portable fan that I could place in the windows, but the noise is irritating.  I also have open windows. However, in the colder weather I can only have them slightly open (there is a small cross-flow thru these windows from facing rooms) because my hands have an extreme reaction to the cold. If I opened the windows to any large degree I would have to wear gloves so thick that I could not handle a paint brush.

Can I safely use this Artisan thinner with minimal cross-ventilation (I only use about 2 - 3 mls (5 mls at the absolute max.) during any one session)?

Do you have any other information that could cause me to be more cautious?

Really appreciate your expert advice, as usual.

Many thanks in advance.

Repairing cracked masonite panel

Question asked 2019-11-27 21:51:13 ... Most recent comment 2019-11-27 21:38:00
Rigid Supports Handling and Transportation Art Conservation Topics Industrial and Non-Traditional Products Other Studio Tools and Tips

​A fellow artist and I collaborated on a piece together, in both acrylic and oil paint on a 36"x48" cradled Gessobord. I applied ArtResin to the piece which was curing perfectly in the storage area on the third floor of an art gallery. I went up to the painting on the third day and found a couple of deep cracks had appeared in the glossy ArtResin. Upon closer inspection I realized the cracks in the resin were a symptom of cracks in the masonite panel. Since it was in perfect condition two days prior, and it wasn't subject to wild fluctuations in temperature, I assume it fell and someone righted it, not realizing it has suffered. 

Now the other artist has been invited to ArtBasel and wants to take this piece. My question is; how can I repair the masonite so the end result is strong and also looks good enough should the piece sell?

I think I have figured out how to repair the resin by sanding it down and reapplying it, but any suggestions for that part are also appreciated.

Thanks in advance!

can linseed oil be used as a sizing/sealing agent

Question asked 2019-11-23 01:43:43 ... Most recent comment 2019-11-23 10:59:02
Sizes and Adhesives Rigid Supports


A poster at the Wet Canvas forums recounted priming a panel with linseed oil. I recommended caution, never having heard of, or used, this technique. Others supported the practice, and said linseed oil would preserve the panel, and would dry to form a good sealant, suitable for painting. An internet search reveals no definitive argument one way or the other. I wonder is there a "last word" on the subject? Cheers!

Stapling canvas: sides or back

Question asked 2019-11-19 16:51:23 ... Most recent comment 2019-11-22 09:58:59
Flexible Supports

I seem to remember reading somewhere long ago (perhaps the old AMIEN forum) that stapling/tacking on the back was purely aesthetic and stapling on the side provided more stability/even tension and so was archivally preferable. Does anyone here have insight into this? Thanks.

Water-Miscible Oils, Revisited

Question asked 2019-11-16 13:22:49 ... Most recent comment 2019-11-19 18:39:44
Oil Paint

​Hello MITRA folks. I've inquired about water-miscible oils (as a option for underpainting) here before, and the response was that there was some concern about their long-term stability, being a relatively new product, because of some of the surfactent ingredients in some of the products on the market. Do you know if there are brands that do NOT incorporate these questionable ingredients? And if there are working practices that would mitigate any possible de-laminating effect down the road? On a related note, could using egg tempera (in the tube product form) be a reasonable substitute for washy underpainting techniques for an oil painting? I'm looking for a solvent-free option that is fluid, longer open time than acrylics, and one that can be left exposed in some areas (i.e. edges) of the finished oil painting. Thanks for any thoughts!

Mounting and framing works on paper

Question asked 2019-10-29 15:40:17 ... Most recent comment 2019-11-09 19:25:28
Matting, Framing, and Glazing Sizes and Adhesives

​Hello dear people from MITRA. 

I wanted to ask some questions about framing and mounting..

I don't know is this an issue in other countries and cities as well, but here in my country i have a serious problem with people who are framers, and with their method so to speak... 

They use mostly masking tapes (or painters tape) i think this is how you call it, mostly yellowish tape that can be ripped with hand easily.

They take the artwork on paper (watercolor, drawing etc.) and place it under  the passe- partout (mat). Then they use masking tape and put it on the 4 corners on the back of the artwork on paper so it will stick to the passe partout. Then they put glass on the front, and for the back they  use cardboard to press or hold the artwork and passepartout together . Close it, and that's it... 

So, i have seen that the right way to frame works on paper is to take conservation (archival tape) to mount the artwork on archival museum board (which they have never heard of) and then to put together passepartout and museum board so that passepartout will just lay over the artwork, Then glass on front, and cardboard on the back and to close the frame...

Since i cannot change their decades old way of framing i have found a store where i can at least buy the archival tapes. 

They will use this tape on the back corners of the artworks to hold it to passepartout. 

So can anyone please advise me which ones to buy for this?  (i will post links)     

(These ones are conservation tapes made of archival safe poliester which is put together with acid free paper with selfadhesive lining. 

and these ones    are a conservation corners (or photocorners) . They are made of 100 % acid free, archival, safe  polypropylene . It contains longlasting acrylic adhesive , 100 % water based

I think i would like to buy the archival tape (1st one) but if there is anyone who can check this and advise me on this, i would be more than grateful. 

Also if anyone thinks there is another solution to this, please say so.  Thank you all very much!

Kind regards

Marko Karadjinovic

yupo paper

Question asked 2019-11-03 15:49:52 ... Most recent comment 2019-11-05 16:42:40
Art Conservation Topics

​Can you paint on yupo paper with oil and will it absorb enough to not peel off over time.  Is it archival/

Gamvar for egg tempera or alternatives

Question asked 2019-10-22 11:46:42 ... Most recent comment 2019-10-31 04:26:45
Varnishes Egg Tempera

​I have a question about varnishes for egg tempera.  Until recently, I used boiled linseed oil, but it is a tremendously problematic varnish which changes the nature of painting (lead white becomes transparent, azurite becomes green etc.)  So I decided to seek something better.  Several substances came to my attention, one of them was GAMVAR.  I tested it and got very unpleasant surprise: wherever Gamvar came into contact with egg tempera paint, dreadful white spots appeared.  NOTE: those were not "blooming", I'd know the difference.  This was some kind of whitish residue that appeared on top of the painted layer, while Gamvar completely sunk into the paint.  Under-tempering is not a factor in this, I temper my paint quite well (egg-shell sheen), and apply nourishing layers often.  I also know that those whitish spots look exactly like when I had to clean gilded parts with mineral spirits, some of it got onto the paint and bleached it immediately.  

My friends who work in oil swear by Gamvar.  I decided to persist and varnish the painting I just finished with Gamvar, and even after 6 consecutive coats, there are lots of sinking as if it goes through the paint like through a sieve.  

Anybody had experience with this or has other varnishing options for egg tempera?  The properties I seek are:

1. Non yellowing
2. Something which would not cause blooming
3. Reasonably strong to protect the painting

High humidity for large canvas

Question asked 2019-10-23 09:46:39 ... Most recent comment 2019-10-24 04:27:21
Flexible Supports Storage Matting, Framing, and Glazing

​A student of mine just asked how she can protect a large cotton canvas from the really high levels of humidity in her new house.

The canvas was passed down to her and it belongs to the family. It is too large to mount on a panel. Because the walls are quite humid in the winter, she fears for the longevity of the painting.

I remember reading suggestions of gilding the back of the canvas of aluminium foil etc. Do you have any suggestion for this problem?

Thank you


Phthalo Green mystery

Question asked 2019-10-02 12:09:29 ... Most recent comment 2019-10-19 14:54:34
Paint Making Paint Additives Oil Paint Scientific Analysis Pigments

Hello all,

I have a bit of a minor mystery that I'm hoping you can help me with.

I have been testing a lot of different paints from various brands when mixed with walnut oils to a more fluid texture and stored in the dark in a box in a wardrobe at room temperature.

This was to find the paints that stay open the longest without the use of clove oil, or other techniques.

As part of this I tested 9 different paints of either PB15 or PG7 (and in one case, a mix of both). From these tests I concluded that Phthalo pigments are indeed fast dryers as all of them except one totally dried in 2-8 days.

The one exception was a tube of Royal Talens Van Gogh Phthalo Green (PG7). This was still open for a few weeks when I had to stop the test and go on holiday. When I got back I thought I'd test all the colours to see if any were still open after all this time.

To my astonishment the paint was still open after 62 days! I then took the paint sample out of the dark and left it in a normal lit room for at least 3 weeks, after which it dried. The smell of the paint is the same as Linseed oil, the texture upon drying is firm (not soft) and the colour the same as other PG7 paints.

I tested this again with both pure paint and paint mixed with wallnut oil, again it stays open even for a few weeks exposed to the light.

I can only think that this paint has been exposed to some kind of anti-oxidant such as it used to preserve cooking oils, as I can't think of another reason why it stays open so long.

I would like a long drying PG7 paint, but I'm concerned about the resulting paint film integrity with using this paint.

I have emailed Royal Talens, but no response yet.

I was hoping you have some thoughts about what might be happening here?


Laser light damage?

Question asked 2019-10-06 15:31:17 ... Most recent comment 2019-10-08 15:52:01
Mural Painting Art Conservation Topics

​About four years ago I was in the Basilica of saint Francis of Assis and there were a number of what appeared to be friar guides using laser lights to direct their groups eyes around the murals high above them.  Could this be damaging to the pigments in the paintings? Hindsight is 2020, but instead of asking them directly I went to a guard and asked if they should be doing this.  "I understand but it's out of my control."

Were my concerns valid ones? I've since noticed it being done, if more briefly, on stained glass windows in the Chartres Cathedral as well.

Regalrez 1126

Question asked 2019-10-08 07:41:37 ... Most recent comment 2019-10-08 11:32:41

​just curious how to adjust the sheen of regalrez 1126?

Wheat and Rice Starch Adhesive Vs. Other Starches

Question asked 2019-10-07 02:45:01 ... Most recent comment 2019-10-07 21:42:04
Sizes and Adhesives

​Hi there! This might be a slightly esoteric question, but I was curious about the use of starch paste as an adhesive for use in paper artifact conservation.

Why are wheat and rice starches favoured over other types of starch, for example corn or potato starch?

Is it due to the ageing properties of the starch itself (I'm thinking for example of how simple wheat flour paste ages poorly due to the gluten content, though this presumably would not be the case with corn or potato, even in unpurified form)?

Or is it other qualities of the adhesive, such as reversability, cost, ease of application etc?

Thanks in advance!

Restoring unvarnished oil paintings

Question asked 2019-10-03 14:39:51 ... Most recent comment 2019-10-07 16:27:42
Art Conservation Topics

​Dear administrator,

I'm thinking whether to varnish or not oil paintings. 

Is it possible to clean old unvarnished oil painting in same methods as restaurator would do with varnished one?

Also, what would be expected result in comparison between the two?

Kind Regards,

Damir P.

Washing unused canvas

Question asked 2017-10-12 15:58:50 ... Most recent comment 2019-10-04 07:44:12
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.

tempera grassa

Question asked 2019-10-03 14:13:35 ... Most recent comment 2019-10-03 16:53:06
Egg Tempera

​Hi maybe you can answer this one. I've always assumed that you could safely paint oil on top of either acrylic, tempera or tempera grassa. But not in the opposite order. But today I met a seasoned painter, who argued that in the isolated case of tempera grassa, you could also paint on top of lean layers of oil paint without it causing any problems. This was because this oil-egg emulsion contained oil as a binder. What you think. I can't find any evidence online to substantiate this.

Metalpoint Grounds

Question asked 2019-10-01 15:03:12 ... Most recent comment 2019-10-01 20:25:47
Grounds / Priming Drawing Materials

Hi.  I'm doing more metalpoint ground experiments and have a few questions.

1. Does anyone know relative hardness (i.e. which is softest, which is hardest) of a cured film of the following binders: gum Arabic, egg yolk, casein, acrylic polymer, vinyl polymer, and oil?    I'm primarily working with water-based metalpoint grounds, but I made an oil ground and found that it works really well; it seems to abrade better than other surfaces, once it has fully cured.  So I'm wondering if an oil base is that much harder and resistant to a metal nib than the above water-based binders. 

2.  Gordon Hanley is a metalpoint artist who, apparently, (as seen in online reproductions of his work) achieves authentic blacks in his drawings (whereas most metalpoint artists get no more than deep grey).  He says he gets black by working with pure silver on a homemade, proprietary ground. Many metalpoint artists would like to know his secret, but he stays mum.

I made an oil based ground that consisted of 1 part Gamblin Brilliant White Oil Paint, 1 part silica, 1 part Liquin.  Not sure how durable such a combo is, but it did yield very dark marks - and, after sitting for a few months, I just noticed that one set of marks now appear genuinely black. (To my annoyance, I didn't note what metal nib made those mark).  The questions are: how durable is that combination of ingredients? And is there anything noteworthy in those ingredients that might account for deep grey metal marks turning black?

3.  I've played with adding different extenders (silica, bone ash, glass, barite, pumice, marble dust, chalk, historic pigments) to metalpoint grounds, to increase abrasion.  Silica gives the best results, which isn't surprising given its Moh's Hardness Scale rating of 7 (harder than any metal nib I use).  What is surprising is that Talc, with a MHS number of 1 (much softer than my metal nibs) also seems to minimally increase abrasion.  I've read up on the properties of talc but it's confusing for a non chemist to distinguish between natural versus milled state, etc. - I just don't understand it all. So my question is, does anyone know properties of talc (i.e. does it have an unusually rough morphology?) that might explain why it improves a metalpoint surface?  Is it accurate that all minerals, even after they've been milled, have an irregular morphology (versus, for example, some modern pigments that are quite smooth and round at the particle level)?

Thanks as always,  Koo Schadler

Underpainting and/or underdrawing for Encaustic

Question asked 2019-09-28 03:12:42 ... Most recent comment 2019-09-29 04:48:58
Encaustic Drawing Materials Egg Tempera Ink

​Hi All,

I am new to this forum and look forward to benefiting from the expertise gathered here.

I am currently working on a project that will involve 13 small panels (each one approximately the size of an A5 piece of paper) to be painted in encaustic - according to a preestablished design (each design being different). The panels themselves are 3 mm HDF panels coated with size and then several thin layers of traditional RSG and chalk whiting gesso. 

So I want to create an underpainting and/or an underdrawing to assist in the image creation before applying the encaustic paint. I'm thinking of using washes of india ink for my underdrawing as well as light washes of egg tempera to begin to establish color relationships. Are either one of these materials going to create an adhesion problem for the wax? I'm thinking not, but wanted to be sure. Of course, I do plan on fusing the painting by "burning it in", as this will allow the melted wax to fuse properly with the ground.

I did create a painting this way approximately 7 years ago. There was not then nor appears to be now any adhesion problem. But I thought I would check with the experts here as most current usage of encaustic appears to be at least fairly coarse if not abstract, so I do not easily find much information on creating recognizable or even detailed images using this technique.

Thanks in advance for your information.

Silverpoint and Egg Tempera

Question asked 2019-09-19 15:20:22 ... Most recent comment 2019-09-20 16:51:23
Animal Glue Egg Tempera Varnishes Drawing Materials

I have a fellow painter asking me about a piece she is creating in silverpoint and egg tempera.  As she rightly points out, the sulphur in egg yolk causes silver to oxidize (in fact, a bit of yolk is sometimes added to metalpoint grounds to speed up oxidation).  She may leave parts of the silverpoint visible in the final painting and doesn't want the silver to tarnish.  She is thinking of applying a layer of rabbit skin glue over the underdrawing, to seal it off, before painting in egg tempera on top.  I have a few questions about this:

1.  Because rabbit skin glue is so hygroscopic, would a very thin layer of platina shellac be a better option for sealing off the silverpoint uderdrawing before moving onto tempera?  

2.  I know there are many examples of egg tempera adhering well atop india ink underdrawings, so I understand ET can adhere to shellac - but if an entire panel is coated with a layer of shellac (as suggested above), is adherance of the tempera a bit more problematic?  If so, would a careful sanding of the shellac layer be sufficient to improve adhesion? 

3.  How porous are rabbit skin glue and shellac?  Would they entirely protect the silverpoint from oxidation (from either egg yolk or atmospheric sulphurs), or are they not sufficiently sealing?  Is a final varnish necessary to make sure that the parts of the silverpoint that remain visible don't tarnish?

4. When silverpoint underdrawings were used in the Renaissance, were they pretty much invariably covered with ink layers before egg tempera was applied?  Or are there Renaissance examples of egg tempera painted directly atop silverpoint?  I'm wondering, if egg tempera is applied directly onto silverpoint (no ink layers in between), do the tempera paint layers sufficieintly seal off the silver from oxidation, or does enough oxygen travel through the tempera to reach the underlying layers and cause the silver to oxidize if in direct contact with the tempera paint layers?  If so, would the resulting oxidation on the silverpoint compromise to any extent the adherance of the tempera to the silverpoint?


Koo Schadler

Stuck oil paint tube caps

Question asked 2019-09-18 02:42:44 ... Most recent comment 2019-09-18 23:04:19
Oil Paint


this is probably one of the dumbest questions you have had, but here goes anyway: I don't always remember to clean the threads on the tubes, and just screw the caps back on after squeezing paint out. I usually get away with it, or having the caps just being a bit tight. But sometimes I may not use that colour for some weeks, or months, and the cap is well and truly stuck. (for some reason it doesn't affect all my tubes).

I saw a video on Youtube which showed someone upending the tube and placing the threaded part into just off boiling water. That  works, although sometimes has to be repeated once or twice more. I then squeeze out the paint that was in the threaded part of the tube and discard it.

I tried to scrape off just the hardened paint holding the cap to the threads, but caps wouldn't budge. Tried using a rag and some multigrips but just broke part of the caps (tubes still salvageable).

Apart from getting my act together and (1) carefully cleaning the threads (and inside the cap) after using the tube, have you got any other better ideas? (2) Is my Youtube hot water method likely to damage the paint in the body of the tube nearest the threads? It seems to look and handle OK afterwards, but just worried that the hot water might damage the paint in the top part of the tube which might cause problems later down the track.

Appreciate your feedback

Drying time for extra acrylic gesso primer to canvas

Question asked 2019-09-18 02:58:56 ... Most recent comment 2019-09-18 22:50:41
Grounds / Priming


How long should you wait between extra applications of this gesso before applying the next coat?

On the container it says to let dry between coats, but I use it to fill in the weave of the canvas to give a smoother surface to apply oil paint on. The canvases are already triple primed by the manufacturer but weave of canvas still obvious, which I dislike. When I apply extra gesso I use a bit of pressure to try and drive it into the weave. I can see/feel when the outer part is dry but can't really know when the deepest part is properly dry.

Does it really matter provided the outer part is dry? state that you should wait 3 days after applying the final acrylic gesso layer before you apply oil paint. Should I wait the same time between coats when applying extra gesso, for reasons given above?

Thanks in advance

Pigment absorption on skin contact

Question asked 2019-09-15 18:49:51 ... Most recent comment 2019-09-16 16:27:53
Health and Safety Oil Paint Pigments

​Dear MITRA administrator,

Can pigment ground in linseed oil without solvent be absorbed in body when one touches wet paint with fingers?

I believe lead white can because M.Rossol writes ''Lead metals, lead oxide and lead nitrate are known to absorb through the skin.'' (Artist's H&S Guide page 157.). But what about others like TiO2, Iron oxides, Cobalt, Manganese, etc?

Kind Regards.

Lascaux Spray Varnish & Wax Medium

Question asked 2019-09-16 08:06:13 ... Most recent comment 2019-09-16 12:02:02

​I have a student who applied ten, thin layers of Lascaux spray varnish on an egg tempera painting; then, after it had sat for a few weeks, applied a layer of Gamblin wax medium on top.  The wax medium felt "sticky" as she applied it so she ended up having to rub it fairly vigorously.  When she lifted her rag, there were traces of pigment on it.  Ten layers of Lascaux, even thinnly applied, should be enough to fully seal the tempera.  It might seem like the solvent in the wax medium dissovled in part the Lascuax, but my understanding is that Lascaux's solvent is alcohol, whereas the wax medium's solvent is OMS.  Am I correct in that?  Any thoughts on what might be going on?

Thanks, Koo Schadler

Paint adhesion to support problem

Question asked 2019-09-12 14:17:56 ... Most recent comment 2019-09-15 01:08:29
Grounds / Priming Oil Paint Rigid Supports


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I have a support that has been stored in my closet for at least ten years. It is Belgian Linen mounted on Mahogany board with Rabbit Skin Glue. It appears to have vertical shiny lines which I would imagine to have something to do with the RSG. The surface does have a slick, slightly greasy feel. 

I began to paint on the panel with a wash of Warm Sepia Extra and Gamsol to do the line drawing as I have done for decades. The head and hair portion are two days old, plenty of time to dry to the touch. When I painted on it the next day the end of my Mahlstick touched a portion that I had done the previous day and took off some paint from the surface of the Warp of the Linen. The next day I took some paint without Gamsol and began to model the darks on the figure. This morning as the video shows I can lightly rub some of the paint away which has never happened before. 

Needless to say I am concerned. Before even attempting to continue I am writing to you, and am shortly on my way to the person that has been making my supports since 1986 so we may possibly see what the problem might be. 

Any insight would be greatly appreciated. I’d like to continue on with this support if possible. My paintings have very little paint on the surface, no medium, and usually about three or four passes.

Chemical Formula

Question asked 2019-09-12 20:51:48 ... Most recent comment 2019-09-12 21:37:10
Drying Oils Paint Mediums Solvents and Thinners

​Dear Mitra Conservators,

I would like to know the chemical formula of linseed oil, stand oil, distilled turpentine, spike oil, and dammar varnish but I have found it difficult to find this information.  Can someone provide this information for me or recommend a source ?

Best regards and thank you for the service your provide to artists,

Hector Hernandez

Varnishing Metalpoing

Question asked 2019-09-12 14:34:21 ... Most recent comment 2019-09-12 15:13:16
Varnishes Drawing Materials

I'm working on a mixed media metalpoint.  I'm using gold, copper, brass, bronze, silver and bismuth nibs to represent the hues of an oriole I'm depicting.  I do not want the base metals to tarnish; additionally, I'm framing the work without glazing.  For both those reasons I'll be varnishing the piece, with either a very thinned layer of platina shellac (the benefits & drawbacks of which we've gone over on the forum, so I won't belabor that issue) or B-72 (I know, a better choice, but I don't like how "plasticy" it feels/looks), then following either isolating layer with an application of wax medium.  Will this be sufficient to seal off the image and inhibit tarnishing?


Koo Schadler

Cutting Absorbency of Traditional Gesso

Question asked 2019-09-12 07:37:23 ... Most recent comment 2019-09-12 14:26:12
Grounds / Priming

When painting oil on top of a traditional chalk & glue ground, to cut the absorbency I generally recommend first applying a thin layer of shellac or rabbit skin glue on the gesso.  Any other recommendations?


Koo Schadler  

Incising into a Ground Layer?

Question asked 2019-09-05 22:14:30 ... Most recent comment 2019-09-09 16:40:33
Acrylic Grounds / Priming Oil Paint

​Hello MITRA folks. Can you suggest an acrylic product that could be used as a ground layer thick enough to draw lines into with a rubber tip and when dry (on panel) can be safely painted over with oil paint? (And how long would the 'open' time be?) Before the research about Zinc came out, I was happily doing this with pale Zinc blends, and then painting into the lines and overall with oil paint. A look I really loved, but lost of few to delamination, and now I understand why... Thank you for any suggestions!

Pumice powder mixed into oil paint

Question asked 2019-09-07 16:08:30 ... Most recent comment 2019-09-09 16:00:11
Oil Paint

​In my search for the best oil medium for thinning oil paint to the extreme without being up overly glossy, I came across a thread that suggested using pumice powder for a matte appearance. This sounds intriguing because my aim is to paint mountainous scenes by first pouring the paint and letting things happen as they do and then working into those poured layers. Some might say to use acyrlis for this type of approach but i'd rather start to explore other ways of getting an alcohol ink type look on the canvas.

Varnishing acrylic and oil paintings

Question asked 2019-09-04 13:45:24 ... Most recent comment 2019-09-05 22:59:56

I have a few questions about varnishing that I would like to clarify:

  1. Some manufacturers claim their acrylic​ mediums to be usable as varnishes as well. I assume that the water-based ones won't work on oil paintings, but can they really be used for acrylic paintings?
  2. Some acrylic varnishes are solvent-based (mineral spirits, etc), and it seems those are the ones compatible with oil paintings. However, are there any advantages to using them on acrylic paintings? Some claim to provide UV protection, but is this relevant and (generally) of higher degree than water-based mediums used as varnishes?

Paint integrity - Medium

Question asked 2019-08-23 13:38:02 ... Most recent comment 2019-08-30 05:45:15
Oil Paint Pigments

​I have a very limited palette. Michael Harding Cremnitz White, Robert Doaks Smalt Blue, Terra Rosa and Lead Tin Yellow GE, Old Holland Warm Sepia Extra and Mars Black. I do have Doaks Gen Ivory as an option. 

Two questions:

I was reading last night on your site that there is a problem with Smalt. I've been using it since 2004 with no problems fully realizing that is just a speck of time. Would it be a good idea to replace mine, if so any suggestions?

I had been using a tiny amount of Mineral Spirits in the past if need_1JG6973_F.jpg. If I need a bit more loose paint would Cold Pressed Linseed Oil be the safest thing to use?

The surface of my canvas has very little paint. I'm including a small work to see. I no longer use medium in my paintings since 2005. At that time I was using Blockx Amber with a little Cold Pressed Linseed Oil and Mineral Spirits. I started using that medium in 1993 again, the paintings look as when they were initially painted but I do realize that is not nearly a substantial amount of time to discern any problems.

Sinking in of umbers

Question asked 2019-08-28 02:11:23 ... Most recent comment 2019-08-28 19:12:52
Oil Paint


just read your document on FAQ's etc, in regard to sinking in of the umbers, apparently because of their clay content (PBr7 from natural iron oxide ore).

(1) I have just noted that W & N make a similar colour, synthetic iron oxide PR101 (transparent brown oxide) which has, apparently, micronised pigment particles which I doubt would contain any organic substances such as the problematic clay referred to above? If I use the latter should I then avoid the sinking in associated with PBr7? (all other things being equal);

(2) If I use an oil-based primed canvas such as lead white (instead of an acrylic gessoed one) would this stop the sinking in, even if I use PBr7? 

Many thanks in advance

Resource of Oil Painting Best Practices

Question asked 2019-08-23 17:53:09 ... Most recent comment 2019-08-27 17:46:50
Oil Paint Solvents and Thinners Studio Tools and Tips Paint Mediums

Can anyone recommend a book, article or website that would teach me the best practices for creating a structurally sound oil painting, especially in layers? I read so much conflicting information on fat over lean, and the use of mediums. I am experimenting with water mixable oils, but I figure that a resource on traditional oils would be helpful if I replace "solvent" with "water." Many thanks.​

Coroplast acid free versus regular

Question asked 2019-08-23 12:33:46 ... Most recent comment 2019-08-26 16:34:52
Matting, Framing, and Glazing Industrial and Non-Traditional Products Other Rigid Supports

I am considering using Coroplast as a support for large (48 x 48) drawings  on archival Tyvek. My main question is whether I need to use acid free or if standard white coroplast is neutral an inert. See more details below.

I have an exhibition coming up very soon that I need to prepare for. My original solution was to use acid free foamcore but its arriving with dented edges so I am exploring alternative more durable materials.

I will use acid free tape to adhere the drawings​ to what ever support I will use. There will not be a frame, but the work will be protected by a sheet of plexiglass that will be spaced away from the work. L screws will mount the work to the wall with custom spacers to separate glazing from the drawings.

In some research online I came across a discussion stating that there is no difference in acidity between the acid free coroplast and colored coroplast that is not acid free (white or clear is what I would prefer). It may be easier to find the regular coroplast locally in the large sheets that I need which is why I am asking if there is a significant difference. I may be able to line the support with an extra sheet of Tyvek as a barrier if that would be necessary.

thanks very much!

Overpainting eco-solvent inks

Question asked 2019-08-23 02:30:22 ... Most recent comment 2019-08-26 12:03:12
Ink Oil Paint Paint Mediums Industrial and Non-Traditional Products Dyes Grounds / Priming Solvents and Thinners Sizes and Adhesives Pigments

​I wish to overpaint in oils a canvas with an existing image in eco-solvent ink. Is there a bonding spray that would permit this? 

Egg tempera varnishing

Question asked 2019-08-25 06:40:40 ... Most recent comment 2019-08-26 11:59:10
Egg Tempera

​I am fairly new to your forum and I am not sure whether is fine to ask a question already placed some time ago.

I am currently at my final year of my Icon painting studies in Russia and I will soon be faced with this dilemma of varnishing. Here at our school they have taught us to varnish using Olifa,boiled linseed oil. This method works well in Russia due to their weather conditions but in my country Cyprus, Olifa tends not to dry and remains sticky. It also doesn't provide enough protection. Apart from that it ruins the warm and cold relationships upon which the icons are built on. Some people tried using Olifa mixed with boat varnish to make the final film stronger. Others just place Olifa for 5 hours remove it, wait for the icon to dry and varnish with an acrylic varnish. This provides some protection from the solvents in the varnish and ensures even spreading of the varnish. I have tried replacing Olifa with Poppy oil that doesn't change the colors and then place the varnish on top. This still is not ideal since this oil as well doesn't seem to dry in my country's  conditions.

I have read your suggestions about PVA ethanol or acetone based followed by varnishing. This is the first time I read about it and I have some questions.

1. Will it be fine to use this method on a freshly painted icon? Wont the acetone or ethanol react with the egg since they are organic solvents? People don't understand that an icon needs to cure before varnishing.

2. Will the isolation layer be even since no oil is present to saturate the ET layer?

3.Does this method provide sufficient protection? People tend to care for icons but not in a proper way which sometimes destroys them

4. Does this method has any effects on naturally occurring pigments such as cinnabar, lapis lazuli, carmine?

Thank you


More questions on 'painting into wet oil paint'

Question asked 2019-08-25 22:36:29 ... Most recent comment 2019-08-26 11:51:47
Oil Paint

​Hi all,

This question possibly should have have put thru the 'post user comment' function on a previous post of mine dated 2019.8.06, titled: Painting into wet oil paint., but I don't know if it would have been spotted and answered, so I have put it here. Appreciate your advice on what is the best way to go about this.

Anyway, after carefully re-reading the moderator comments I still have a little doubt concerning my latest portrait project and would appreciate your advice again:

About 2 weeks ago I did a very thin underpainting in traditional oils straight from the tube, onto an acrylic gesso primed canvas (only professional quality name-brand oils/canvas used. As the canvas was triple-primed by the manufacturer I did not add any more gesso). No solvents or mediums. When I touch it, it is very slightly tacky and rubbing a tissue on the painted area (burnt sienna PB7/PR101) produced a very slight stain on the paper. Both these effects were only very slight.

I have been painting for some years and in the past have used an OMS thinned wash for initial underpainting, which dries fairly quickly. I am trying to avoid using solvents now, just paste paint.

I have tried the 'fingernail indent' test but the paint is so thin that I couldn't make much of this test.

Should I wait until the painting is completely dry to the touch before applying a further layer? I have never been so exacting before, but now are producing paintings for others so want to avoid any issues down the track. 

Many thanks again

Lavender spike oil as a solvent/thinner

Question asked 2019-08-21 16:58:09 ... Most recent comment 2019-08-23 19:07:35
Solvents and Thinners


I added this onto the tail end of another discussion but probably should have started a new question, so here goes:

I note that in this discussion it was said that.. using large amounts of an essential oil is detrimental. Is using Lavender spike oil: tube oil paint in 1:1 or even up to 2:1 (max.) OK?

I.E. what is the dilution limit you can use in an underpainting and still achieve adequate adhesion?

Recently reading an article from Jerry's artarama re this oil indicates that the vapours are non-toxic and it evaporates about the same speed as OMS, can be mixed with mediums, and a safe alternative to OMS. (no special ventilation requirements). My understanding of the MSDS also gives no concerns unless you swallow it or get it in your eyes. The only drawback seems to be the high price as compared to OMS.

Many thanks in advance

Sizing Handmade Papers

Question asked 2019-08-21 10:15:45 ... Most recent comment 2019-08-23 18:21:20
Gouache Ink Sizes and Adhesives Watercolor

​What would be my options for sizing an absorbent handmade paper (i.e. a Japanese paper) for a subsequent ink, watercolor and gouache painting? It would be framed under glass or plexi when finished, of course. Thanks for your thoughts, MITRA folks!

Paint integrity - Medium

Question asked 2019-08-23 13:30:57 ... Most recent comment 2019-08-23 13:00:00
Oil Paint Pigments

No gamsol but still fat over lean process

Question asked 2016-11-28 16:18:20 ... Most recent comment 2019-08-20 19:29:18
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?

Thinning oil paints with solvents

Question asked 2019-08-19 19:05:24 ... Most recent comment 2019-08-20 19:09:57
Oil Paint

​RE: how much can you thin down tube paints without encountering adhesion problems? I have frequently read that the maximum dilution of solvent: oil paint is somewhere between 1:1 to 2:1. Any more than this will leave the paint film underbound, i.e. not enough oil binder to stick the pigment to the canvas. But recently I read/heard somewhere that it doesn't matter anyway provided you paint over this immediately with paint layers with much less solvent as subsequent layers would contain enough binder to provide adequate adhesion. I have watched numerous YouTube videos of professional artists using really watery washes (the wash runs down the canvas) to either tone the canvas or lay-in a drawing. I have seen this so many times (an in art classes) that if it was such a detrimental practice to the longevity of the final painting surely they would have changed their practices by now. After all, if you are doing paid portrait commissions and a few years later they fail in some way then that would be disasterous for business. How do they get away with flouting the common sense 'rules', or doesn't it really matter provided you paint immediately into this watery wash with thicker paint?

Would love to hear some definitive statement on this.

Many thanks

Filling in the weave of a canvas

Question asked 2019-08-19 18:44:38 ... Most recent comment 2019-08-20 18:39:07
Grounds / Priming


with regards to using a canvas with a medium textured weave (or any but the finest weave for that matter) I have recently read that it is best to even out the surface with extra acrylic gesso so that the "ground equalizes  the surface of the support." .........."this would involve losing the grain or texture of the canvas, so that oil paint layers applied over the painting ground like down flat and evenly." (P295 Pip Seymour, The Artist's Handbook, 2003.) I have often wondered about that, but this is the first time I have seen it in print from a seemingly reputable source.

I would prefer to skip this extra gessoing if possible, but is it best practice to follow Seymour's advice? It does seem technically logical what he says.

Appreciate your expert input,

Many thanks

Ampersand gessobord panels

Question asked 2019-08-15 23:03:49 ... Most recent comment 2019-08-18 22:49:31
Rigid Supports


Over the years I have used a number of surfaces for painting with traditional oils, including stretching my own canvases, etc. I am over this now and just want to paint using commercially prepared surfaces. I dislike the 'give' when you are painting on stretched  canvas and will probably concentrate on rigid panels. The only quality commercially prepared panel I could find is Ampersand gessobord which, they claim, has 2 layers of 'seal' between the panel and acrylic gesso primer and support-induced discolouration will not occur. They state the only substance left in the panel during manufacture is natural lignin (glue). I have recently painted on a small sample panel and then tried to scrape the paint away from the gesso without any success. I then tried to dig into the panel to try and seperate the gesso but no go. The panel itself does not crumble and the whole thing appears sturdy, at least to my basic testing. Ampersand claim they are archival and will last over 200 years. state that rigid supports are more archival than flexible ones (Canvas, linen). 

I have no association with Ampersand except as a customer. I have more recently begun a portrait in oils on a larger gessobord. I did an underpainting with thinned watercolour (according to this is fine provided the layer is thin and you let it dry properly. They also say it can be re-worked by simply wetting it) which means I can avoid solvents altogether, hence my reason for using a gessoed panel. I don't want to use panels with canvas stuck on them as youy don't know if SID will occur and the textile can still move anyway due to temperature and humidity changes. Where I live it can get over 40 deg. Cel in summer at times.

I know that Ampersand make other panels, but I want one ready to paint on and with the Archival seal, hence Gessoboard. They only disadvantage is that the larger panels have to be in a cradle which is quite expensive. The smaller ones need to be framed, which has to be factored in, cost-wise. For less important works I would just go back to stretched canvases. I use cheap canvas panels for quick studies.

Am I on the right track? Are Ampersand gessobords really a quality archival surface? I really want to find a good quality pre-prepared gessoed panel and hope these Ampersand ones fit the bill.

Appreciate your comments,


Painting over a 10 year-old underpainting

Question asked 2019-08-15 02:38:56 ... Most recent comment 2019-08-16 16:50:35
Oil Paint

​Hi all,

I did an underpainting (self portrait) about 10 years ago. It was one initial thin layer either scrubed in tube paint or with a bit of OMS added. I think it possibly was the former as some areas have a slight sheen, but most of it is matte. I would have used the same process across the entire canvas, not with OMS in some areas and scrubed-in paste paint in others. I was reasonably accurate as far as drawing goes but no details. I didn't use OMS much then, as now.

For some reason I put this aside to dry and couldn't get the drive to re-start it due to a lengthy illness in the family, then eventually forgot about it. I am almost certain it was W & N acrylic gesso triple primed. It is a stretched canvas and there is no indication of paint/oil penetration to the rear of the canvas. It is life-size from top of a cap to below belt and I am reluctant to throw it away as it was part of my art journey at that time. The canvas probably needs tightening a bit.

I have read some of the discussions here about pentimenti; scraping, sanding and wiping with OMS and would appreciate your comments on my proposed method: 

(1) Clean the whole canvas with OMS on a lint-free cloth. Let this dry. (2) As there are  no raised areas/impasto, or indeed any surface imperfections, I would then sand it lightly to give a uniform matte surface. Taking care not to damage the acrylic gesso. Clean any particles off completely and (3) wipe it down again with OMS. Let this dry, then (4) apply a thin layer of titanium white. (5) Let this dry (fingernail indent test) then start painting in thin layers of paste paint straight from tube until I get to the desired finish.

Probably I should start a new painting but I want to re-use this existing canvas. If one day it 'fails' then that's fate I suppose. 

Many thanks in advance.

Painting over an existing portion of a painting

Question asked 2019-08-05 10:58:48 ... Most recent comment 2019-08-14 20:00:16
Oil Paint Grounds / Priming

​I have a painting that was completed in February. It is oil on a ground of Golden White Acrylic Gesso on a cotton support with wood stretchers. Paint straight from the tube, Old Holland. Occassionaly wash a brush out in Gamsol but blot on a rag to remove the liquid. I paint very thin, this particular portion may have one or two coats primariliy made of greys, some red in other areas. I believe it was Titanium White, Mars Black and Cad Red Purple. A tiny touch of Old Holland Cyan Blue in someof the Greys.IMG_0866.jpg The texture of the canvas is easily seen and felt. I would like to replace that portion with a Union 76 Ball. This gives you the idea of color I will be dealing with. I have ideas of how to do this, but I would prefer to ask you as I have never done this before and want to do it the best way for archival purposes. 

I appreciate any and all help and am happy to supply any additional information necessary.

Removing water stains from oil on linen painting in progress

Question asked 2019-07-17 01:47:35 ... Most recent comment 2019-08-14 19:52:34
Oil Paint Flexible Supports Solvents and Thinners Other

​Dear MITRA,

I am about to resume work on a large format oil on linen diptych after it had to be placed on the back burner for a few years.  At my previous studio, I had some mysterious leaks or perhaps a humidity condensation issue that periodically dripped a pale, thin brown liquid from various areas of the ceiling. After moving to a different space, I discovered that some of this liquid had apparently hit the floor in front of one of these large oils, and then splashed back up onto the lower area of the painting. Luckily the drops were so small that the linen was not damaged, but a series of small water stains/rings were left behind. I tried to gently clean them off with a touch of distilled water, but that wasn't strong enough. OMS worked better, but once the OMS evaporated, you could still see a fainter trace of the whitish-looking rings. Should I try artists' rectified turpentine, then wipe away the turps residue with OMS? If any micro-pores were opened up in the paint as a result of using the stronger solvent, it might increase adhesion anyway since the paintings have been waiting for so long for me to complete them. Please let me know how you think I should best proceed.

If it matters, I am using oils made with walnut oil, and initially used a solvent-based alkyd medium, then a walnut/alkyd. 

Thanks very much!

Rembrandt's paintings question

Question asked 2019-08-13 15:27:24 ... Most recent comment 2019-08-14 19:41:19
Art Conservation Topics Oil Paint Scientific Analysis Technical Art History

​The Rembrandt paintings I have seen in the National Gallery in London (and others online) have a strong dominant yellow-brown hue range. Is this just down to the pigments used and his palette preferences, or is some of this the result of yellowing varnish?

Using natural soil pigments on paper?

Question asked 2019-01-24 06:06:43 ... Most recent comment 2019-08-14 19:00:36
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!

Martin F. Weber "Cleaning Solution for Oil Paintings

Question asked 2019-08-12 08:50:58 ... Most recent comment 2019-08-13 19:30:00
Art Conservation Topics

Hello all.

I am looking for any information about this product.  It has been discontinued by Weber and there is very little information provided by the manufacturer.  Online searches for data about it and its intended use is also not popping up.  Does anyone have information they care to share?


Mike Townsend

Fix Charcoal Underdrawings

Question asked 2019-08-11 18:26:07 ... Most recent comment 2019-08-11 22:23:41
Oil Paint Drawing Materials


I’m working with compressed charcoal #2B, #4B and #6B underdrawing on linen canvas and Williamsburg Lead Oil Ground. I would like to control where the charcoal mixes with the lead linseed oil underpainting.

I’ve read two articles on Just Paint hoping I might find a solution but in both cases they don’t recommend using MSA or a retouching varnish.

1) Why Oil Painting Over MSA or Archival Varnish Is Not Recommended

2) Oiling Out and the Cause of Dead Spots in Oil Paintings

I’m considering two options: 

1) Use Williamsburg Alkyd Resin, cut with Turpentine or Gamsol 1:1 or 1:2 and spray a thin layer over the charcoal drawing before applying the lead oil paint.

2) I’ve tested this formula: linseed oil, damar resin (5-pound cut)  and turpentine (1:1:3), and after waiting 1-3 hours, I applied the lead oil paint. This test did not to work very well since the thin retouching varnish layer disolved when I applied the lead oil paint.

I would appreciate any feedback about the two options mentioned and an alternaitive approach.

Thanks so much,


Re: clarification on "Confusing concepts in oil painting...etc"

Question asked 2019-08-06 19:52:16 ... Most recent comment 2019-08-08 02:27:55
Oil Paint


fascinated by this discussion re abandoning the fat-over-lean and thick-over-thin that we have been taught. From the comments made about 'glazing' i.e. just use paint straight out of the tube ( = paste paint) and with a stiff brush apply it thinly, it would seem that you can paint each layer thinly, even the final one.

Appreciate your advice on what I wish to do in constructing a non-toxic painting (no solvents): (1) for the initial layer I do a block-in drawing with e.g. burnt sienna. This layer is quite thin and I 'tonk it out' (i.e. put absorbent paper towel on top and rub most of the paint off). I am left with a thin layer. This would approximate the idea of an initial layer using a solvent/oil wash. I think the oil in subsequent layers should be able to penetrate this and bind to the canvas.

(2) When doing indirect painting, for subsequent layers I will apply paste paint thinly (as per your advice), allowing each layer to go touch dry before applying the next, until I reach my final degree of finish. i.e. EACH LAYER is paste paint applied thinly. I plan not to use any added oil or medium because I dislike the slipperiness that this causes. From your original article these additions appear unnescessary anyway.

Appreciate your feedback

Painting into wet oil paint

Question asked 2019-08-06 20:33:10 ... Most recent comment 2019-08-08 02:14:39
Oil Paint


when doing indirect oil painting how long should you wait before you apply the next layer? (using paste paint straight from the tube, unaltered in any way). From my understanding of artists comments it would seem commonplace for them to e.g. start a painting in the morning; then have a lunch break, then return to the painting to add further layers in the afternoon. I have also heard that some artists will overpaint the following day(s) because the iniitial painting is still wet. Stating that this slow drying was one of the advantages of oil paint in that you could continue to work on the same painting day-after-day.

From one of the articles on this forum it discusses how oil paints dry through a process of oxidative polymerization i.e. oxygen permeates the oil paint and starts the long, slow process of cross-linking of the binder molecules until a solid eventuates. Subsequent layers slow the ingress of oxygen down into the underlying layers but don't stop it. This process is faster at the start, then slows down apparently. 

If I was to apply additional paint to a partially dried layer does this have any detrimental effect on the polymerization of underlying layers? For example, in the case stated above where I return to a partially dried painting the same day, or the following day(s), will I do permanent damage? Or will it have no negative effect on the painting as a whole? It seems such a common practice.

I realize that enviromental factors come into play in that in hotter weather the paint will dry faster than in mid-winter. But I have never heard this being a factor in relation to the above scenario.

Another reason for my question is that in our summer time it can get really hot, well into the 30 degrees ,or higher, and the paint will start to tack up a little bit even after just a couple of hours. Should I stop then and let it go touch-dry, or OK to keep painting?

Appreciate your advice

Pyrrole Red

Question asked 2019-08-06 10:12:52 ... Most recent comment 2019-08-06 19:06:25

​I'm working with a new pigment, Pyrrole Red PR 254.  It resists wetting, so I added a bit of alcohol to disperse and convert it to a paste.  Usually once a pigment has successulfy dispersed in water, and it dries out, adding more water readily rewets it.  However when the Pyrrole paste dried out, adding more water didn't reconvert it to a paste; I had to add more alcohol.  I'm interested in this, as well as any other comments on Pyrrole Red, which is new to me.

Thanks, Koo Schadler

Confusing Concepts in Oil Painting: Fat over Lean... Thick Over Thin... Thick Over Lean... Whatever... Let's Get Rid of Them.

Question asked 2019-08-01 01:19:37 ... Most recent comment 2019-08-04 14:21:20
Oil Paint

Let's toss out the concepts of “fat over lean” and for that matter “thick over thin” (or the confused “thick over lean”) while we are at it, and let's consider the physical structure of the paint.

To help you to understand the properties of oil paint, it is helpful to understand the relation between the pigment and oil. One way to think about the relationship between pigment and binder is a brick wall. Every mason knows there is an ideal ratio of mortar to brick. Too much mortar and the wall is weak. Not enough mortar and the bricks fall apart.The same relationship exists between the pigments and binder in dried paint. We call this relationship or ratio the pigment volume concentration or PVC. Pigment volume concentration (PVC) is the volume of pigment compared to the volume of all solids. If paint has a PVC of 30, than 30% of the total binder/pigment is pigment and 70% is binder solids.

The point at which there is just enough binder to wet pigment particles is called the critical pigment volume concentration (CPVC). For almost all colors this is between 45% and 55% PVC. Films with lower concentrations of pigment have more gloss but as the PVC increases they become increasingly matte. Films with high percentages of pigment are more permeable to moisture and susceptible to solvents. This is because with more pigment, there is less binder to fill the voids between pigment particles. This porosity leaves the film open to the environment. Films with higher pigmentation have increasingly lower tensile strength.

Most paint in tubes contain enough binder to wet and envelope pigment particles and so are at about the critical pigment volume concentration for that color. The variation in the pigment volume of particular colors between brands are due to the type of oil used, the amount of oil (some paint makers may choose to make their colors softer or thicker) and the amount of additives.

So the best way to discuss paint is by understanding this relation between the pigment and oil which is expressed as the pigment volume concentration (PVC). Oil paint(straight out of the tube is in the form of a paste and is usually at its CPVC. Adding oil lowers the PVC of oil paint, while adding solvent potentially increases the PVC (high PVC). Hence the ideal paint is a paste paint and this is why the admonition to “apply thick paint thinly” or work with paste paint in thin layers, is the optimum way of using oil paint.

From this it is clear that paint consists of both liquid and solid components. In the case of oil paint, the liquid component is a drying vegetable oil. The oil undergoes chemical and physical processes that change it from a liquid to a solid, which process is called “oxidative polymerization”. Oil is the binder or glue that holds the pigment particles (solids) together and adhered to a substrate.

When it comes to adhesion oil is the glue. While many artists believe that mechanical adhesion is most important when it comes to adhesion of paint to a substrate, what is more important is “dispersive adhesion”, which does not rely on absorption into a substrate or surface texture (although the latter improves dispersive adhesion) but rather on surface energy and polarity. Hence, paste paint adheres better than paint that has been heavily diluted with solvent (high PVC) even if it is partially absorbed into the substrate, because it has less oil or binder to adhere to the surface of the substrate.

Requesting Explanation on posting: Confusing Concepts in Oil Painting....

Question asked 2019-08-03 11:22:33 ... Most recent comment 2019-08-03 19:18:53
Oil Paint

Thanks for that great explanation on PVC for oils! I have 4 follow up questions -  If we are to use the correct PVC for our oil paintings and adhere to the "paste paint adheres better" approach, then does this (1) eliminate the initial thinned out under painting stage or use of a light colored undertone for the canvas? (2) eliminate the oiling out between paint layers? (3) are we better off by eliminating any additional Alkyd mediums to help make the oil paints more fluid? (4) and lastly, how would our applications of a "glazing" layer for special effects, be adjusted to keep everything in a PVE balance?


Amount of zinc in titanium white oil paints - some information

Question asked 2018-03-09 14:17:46 ... Most recent comment 2019-07-28 22:20:22
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%."

Polyester/cellulose mix paper

Question asked 2019-07-24 11:52:07 ... Most recent comment 2019-07-27 14:39:09
Drawing Materials Flexible Supports Industrial and Non-Traditional Products

I have recently found blank rolls of wallpaper (160+ gsm), sold as a home decoration solution. They're made from a mix of polyester and cellulose fibers, and I was wondering about the feasibility of using that paper as a drawing/painting surface. Given the better aging properties of synthetic fibers, would the added polyester content increase the longevity of such paper, compared to pure cellulose papers? ​


Question asked 2019-07-26 14:34:28 ... Most recent comment 2019-07-26 22:27:01
Grounds / Priming

​Caparol ( a german product ) is very useful for grounds ( mixed witjh chalk and lithopone )Is it available in America, somewhere?

Indian ink pitt pen drawing painted over with gouache

Question asked 2019-07-24 15:39:31 ... Most recent comment 2019-07-24 18:59:01
Gouache Ink Pen

​Hello dear people from Mitra!

I have a question about mixing materials.

I have asked already about compatibily of indian ink and gouache, and i know it is compatible and mixable, since i had answers from good people from your forum and i saw many old master artworks that were made precisely with these two techniques.

What worries me is, that i have used Indian Ink pitt pen and i did full ink drawing, with deep crosshathing and deep darks, so i did a lot lines with it. 

This was done on thick watercolor paper.

And i really wasnt happy with the end result, but saw the potential in the work, so i reworked or painted over the whole drawing with artists quality gouache (using black and white only).

The works looks good now, but i am intersted is it ok that i did this?Will my work be ok?

And if there are no mistakes visible now, and the work is one week old, does that mean that everything will be ok in future?

Thank you

Marko Karadjinovic

1st MURAL Opportunity- Questions on how to get started

Question asked 2019-06-29 11:28:19 ... Most recent comment 2019-07-22 20:16:13
Acrylic Mural Painting Handling and Transportation Rigid Supports Paint Making Pigments Grounds / Priming

Hello, I was wondering if someone might be able to help me.

I actually have 2 mural opportunities, but right now I'm trying to focus more on one over the other because it seems more 'involved.'

One piece is to be mounted outdoors.  The other piece is to be placed over doors- that is to say, I believe the intention is that it be painted directly on them.  I do not know the door material or their dimension- nor the dimensions of the outdoor mural- but I do know the doors will have to function.  The mural-side of the door is at the interior of the building, the other side is to the exterior, like a garage door. It's a metal roll-up door.


I need to figure out exactly what I need to spend in order to complete each project.

I currently have:

  • Red Oak Plywood- Six 36in*36.5in pc.'s & 15 1Ft. sq. pc.'s all 3/4in. Thick
  • 10pack mini rollers for smooth-semi smooth surfaces - what should I use rollers for vs. brushes? Do I clean to re-use them or are they a single-use type of product?
  • 76mm angled Poly-blend bristle brush, for smooth & semi-smooth surfaces
  • 10 kit HDX Nitrile Disposable Gloves- 'not for use w/ chemicals'
    • Will these work w/ Varathane, GOLDEN Isolation Coat, & Primer?
  • KILZ 2 Latex Primer/sealer/stainblocker Multisurface (Drywall, masonry, galvanized, & more*) Interior/Exterior Water-based- re-coat in 1hour
  • Varathane Brand Ultimate SPAR URETHANE?, Oil-based, clear gloss- Recommends 3 coats & min 4hours dry time(sanding only if drying for 12+ hours) ==> notes cancer & reproductive harm as well as the need for adequate ventilation, but also the harm go humidity
    • Can I use this product outside?- where should I let it dry?

It has been recommended that I get:

  • sand paper. 200 grit- I would be hand sanding to remove splinters - specif. @ he edges where the wood was cut, but I'm assuming I'd have to do the entire board for the primer to adhere - so I'm wondering if there's a correct way to do this...

I think I need:

  • Goggles
  • Respirator
  • Coveralls 
  • Knee Pads
  • Mixing & Storage Containers
  • 1gal. Heavy Body Acrylic Paint-,at least 6 colors- including neutrals? (white, black, brown)
  • 1 Gal. Isolation Coat
  • 1 Gal. Solvent- for the Varathane?, I don't know the exact details of this product, but when I looked up polyurethane, it req.'d a solvent to be used
  • Mounting Hardware
  • Probably additional Painters Tape & Brushes

All 'clothing items' are for the Varnish & finish products- everything appears to be highly toxic, don't know if there are safer alternatives.

All amts were 'guess-timated' before the addition of the 2nd mural piece and it's different setting.


I am still trying to come up with some sketches to determine the overall composition, but I am wondering:

  • How can I go about choosing colors?- The room is full of very 'non-modern?' colors, very little blues, purples, or even oranges and the colors are very muddy and dark.  I would like to choose a period-appropriate color scheme but still add some brightness to the colors I choose and some naturalistic purples and blues that go with the theme of the piece.  I want to make sure I have a large variety of colors, but not purchase unnecessary colors I could just take the time to measure out and mix.
    • Example- If I have a largely white background, fo I need to purchase white paint, or can I just use the Primer? Do I tint the Primer to make other neutrals or do i need to use paint
  • How can I go about estimating and pre-mixing any batches of specific colors to work with?
  • Is it possible to follow and early-1900s 'recipe' for specific colors and get a somewhat accurate result using paints purchased today?

I'm thinking the wood panels would be used for the outdoor piece that would be on the side of a house and would not move.

Some or all of these panels may also need to be shipped... I'm thinking some of the smaller panels could be used to flank the large doors.  The large panels may have to be shipped with some kind of mounting instructions.

I currently trying to read through various MITRA posts, but these are the more pointed inquiries I can think of for myself...

Thank You

Old Holland Zinc white

Question asked 2019-07-20 19:05:21 ... Most recent comment 2019-07-21 21:47:30
Oil Paint

​The Old Holland safety data sheet for their zinc white oil paint lists alongside 70-90% zinc oxide.   3-5% titanium dioxide.  Which strikes me as an interestingly odd thing to do.  Would there be any advantage to adding such a small amount of titanium white to an otherwise pure zinc white paint?


Need for sealing under oil grounds over acrylic primer on hardboard?

Question asked 2019-07-20 12:26:50 ... Most recent comment 2019-07-20 20:45:10
Grounds / Priming

​Dear Moderators Please excuse my "test" question posted prior to this one. I've been having a lot of trouble with the question form. This is the 3rd time I've tried to post this question. I have primed a number of unsealed hardboard panels with 3 coats of acrylic primer and plan to follow up with 2 coats of lead primer. Should I have sealed the panels first eg with a PVA or acrylic resin emulsion? Looking forward to your responses. Kind regards, Jenny


Question asked 2019-07-20 12:21:08 ... Most recent comment 2019-07-20 12:20:00
Grounds / Priming


Sealing Graphite under Oil Paints

Question asked 2019-07-19 12:59:16 ... Most recent comment 2019-07-19 16:21:14
Oil Paint Other Paint Mediums Pencil Drawing Materials Ink Pen Studio Tools and Tips

​Hello MITRA folks...I would like to seal a graphite or India Ink line drawing on canvas or board that has been 'gessoed' with acrylic dispersion fluid. The drawing would then be painted over with oil paints, but some of the drawing linework may remain exposed in the final painting. I would like to know what my options are for sealing the linework that would be 'durable' if left exposed in the final, varnished image, but also a good bond with the subsequent oil paint in some areas. I'm thinking acrylic matte medium, but maybe there are other options...? Thank you for your thoughts!

Shaping brushes after washing.

Question asked 2019-07-07 20:15:27 ... Most recent comment 2019-07-16 22:28:29
Oil Paint Paint Additives Studio Tools and Tips

​As stated, I want to be able to wash brushes with soap and water, shape them with the help of some product, and use them in the morning without having to rinse them in sovent.
Candidate products so far are saliva, gum arabic, egg white, and maybe milk. I'm leaning toward gum arabic.

My question is, will any of these unduly affect the paint film if it is not washed out of the brush before using?

Ron Francis.

Traditional Gesso

Question asked 2019-07-11 10:26:10 ... Most recent comment 2019-07-11 16:00:49
Grounds / Priming

When I first became a tempera painter, I experimented with many different recipies for traditional gesso (gleaned from various books – there was no on-line world back then!).  I got both good and bad results (some gessoes developed cracks).  Eventually, after much reading and experimenting to better understand the properties of traditional gesso, I arrived at what seemed a solid recipe based on ratios versus specific measurements; it's always yielded a good, reliable surface, and I've heard from many artists with whom I've shared the recipe that they too use it with success. 


I've found that a mix of 1 part glue to 16 parts water, then 1 part of this glue water combined with approx. 1.5 parts chalk or gypsum, yields a not too soft, not too hard ground.  However there is some variability in the water to glue ratio – more glue in the mix yields a harder ground, less glue a softer ground. So an artist has flexibility in the recipe depending on what sort of ground he or she wants to work on.   On the other hand, in my experience, if one strays too far outside certain parameters in the water to glue ratio, the resulting ground is either too hard (anything beyond about 1 part glue to 12 parts water = too much glue in the ground) and is prone to cracks; or too soft (anything less than about 1 part glue to 20 parts water = too little binder) and the ground becomes friable.  


Recently I read a gesso recipe from a paint tech, whose knowledge I trust and respect, which recommends a ratio of 1 part glue to 5 parts water.  I was surprised by this number; it seems way too much glue to me, and in fact I have a panel made from this recipe that dramatically cracked (see attached image). Gesso Panel cracks.jpg   However the tech feels confident that a 1 glue to 5 water ratio is reasonable for gesso, and also has panels made from this recipe that haven't cracked.  (FYI, I understand that glue is not the only reason gesso can crack – changes in temps, humidity, wood grain telegraphing through, dropping a panel on its edge, etc. also can cause cracks…)


I've always felt pretty confident of my understanding of true gesso – that too much glue in the mix is problematic, and anything beyond about 1:12 or maybe 1:10 tops is too much glue – but now I'm wondering if there is more flexibility in the ratios for true gesso than I realized.  Any thoughts? I want to make sure I'm understanding gesso correctly. 


Thanks,  Koo Schadler 

Which side of Dibond panel?

Question asked 2019-07-01 13:25:14 ... Most recent comment 2019-07-08 02:20:41
Rigid Supports Acrylic


I am using Dibond panels for my acrylic paintings. I usually sandpaper the polyester coating and then clean it with isopropyl alcohol before applying some acrylic gesso on top of it... Both the panel sides are covered with a poyester coating. One side is glossy, the other is mate. Can I use any of them? Or is one of them better for adhesion? Thank you.

Best regards,

Thomas Ehretsmann

Adhering canvas to plywood wood panels

Question asked 2019-07-01 20:14:53 ... Most recent comment 2019-07-01 22:12:24
Rigid Supports

​A previous post discussed using shellac to seal engineered wood panels.   (Note: I'm not yet using the pigmented shellac recommended in the post above but will for future projects)  Anyway,  I have been gluing pre-primed canvas to cradled plywood.  I use 2 coats of undiluted shellac (as the manufacturer recommends)  to seal all sides of the panel and cradle.   I then used PVA glue to adhere the canvas.  I was just wondering if there were any potential issues with this approach such as poor adhesion of the glue to the shellac or future delamination of the shellac under the canvas?  Should I be diluting the shellac to increase absorption and ensure good tooth for adhesion?  

1st MURAL Opportunity- Questions on how to get started

Question asked 2019-06-29 11:19:03 ... Most recent comment 2019-06-29 11:13:00
Mural Painting Paint Making Grounds / Priming Handling and Transportation Rigid Supports

Hello, this is Martha Rose.  I was wondering if someone might be able to help me.

I actually have 2 mural opportunities, but right now I'm trying to focus more on one over the other because it seems more 'involved.'

One piece is to be mounted outdoors.  The other piece is to be placed over doors- that is to say, I believe the intention is that it be painted directly on them.  I do not know the door material or their dimension- nor the dimensions of the outdoor mural- but I do know the doors will have to function.  The mural-side of the door is at the interior of the building, the other side is to the exterior, like a garage door. It's a metal roll-up door.


I need to figure out exactly what I need to spend in order to complete each project.

I currently have:

  • Red Oak Plywood- Six 36in*36.5in pc.'s & 15 1Ft. sq. pc.'s all 3/4in. Thick
  • 10pack mini rollers for smooth-semi smooth surfaces - what should I use rollers for vs. brushes? Do I clean to re-use them or are they a single-use type of product?
  • 76mm angled Poly-blend bristle brush, for smooth & semi-smooth surfaces
  • 10 kit HDX Nitrile Disposable Gloves- 'not for use w/ chemicals'
    • Will these work w/ Varathane, GOLDEN Isolation Coat, & Primer?
  • KILZ 2 Latex Primer/sealer/stainblocker Multisurface (Drywall, masonry, galvanized, & more*) Interior/Exterior Water-based- re-coat in 1hour
  • Varathane Brand Ultimate SPAR URETHANE?, Oil-based, clear gloss- Recommends 3 coats & min 4hours dry time(sanding only if drying for 12+ hours) ==> notes cancer & reproductive harm as well as the need for adequate ventilation, but also the harm go humidity
    • Can I use this product outside?- where should I let it dry?

It has been recommended that I get:

  • sand paper. 200 grit- I would be hand sanding to remove splinters - specif. @ he edges where the wood was cut, but I'm assuming I'd have to do the entire board for the primer to adhere - so I'm wondering if there's a correct way to do this...

I think I need:

  • Goggles
  • Respirator
  • Coveralls 
  • Knee Pads
  • Mixing & Storage Containers
  • 1gal. Heavy Body Acrylic Paint-,at least 6 colors- including neutrals? (white, black, brown)
  • 1 Gal. Isolation Coat
  • 1 Gal. Solvent- for the Varathane?, I don't know the exact details of this product, but when I looked up polyurethane, it req.'d a solvent to be used
  • Mounting Hardware
  • Probably additional Painters Tape & Brushes

All 'clothing items' are for the Varnish & finish products- everything appears to be highly toxic, don't know if there are safer alternatives.

All amts were 'guess-timated' before the addition of the 2nd mural piece and it's different setting.


I am still trying to come up with some sketches to determine the overall composition, but I am wondering:

  • How can I go about choosing colors?- The room is full of very 'non-modern?' colors, very little blues, purples, or even oranges and the colors are very muddy and dark.  I would like to choose a period-appropriate color scheme but still add some brightness to the colors I choose and some naturalistic purples and blues that go with the theme of the piece.  I want to make sure I have a large variety of colors, but not purchase unnecessary colors I could just take the time to measure out and mix.
    • Example- If I have a largely white background, fo I need to purchase white paint, or can I just use the Primer? Do I tint the Primer to make other neutrals or do i need to use paint
  • How can I go about estimating and pre-mixing any batches of specific colors to work with?
  • Is it possible to follow and early-1900s 'recipe' for specific colors and get a somewhat accurate result using paints purchased today?

I'm thinking the wood panels would be used for the outdoor piece that would be on the side of a house and would not move.

Some or all of these panels may also need to be shipped... I'm thinking some of the smaller panels could be used to flank the large doors.  The large panels may have to be shipped with some kind of mounting instructions.

I currently trying to read through various MITRA posts, but these are the more pointed inquiries I can think of for myself...

Thank You,

Martha Rose

Sennilier Gloss Varnish Problem

Question asked 2019-06-25 17:30:16 ... Most recent comment 2019-06-26 12:01:33

​After applying the Sennelier gloss varnish on well-cured, heavy impasto oil paintings, the varnish clouds and flakes off with the slightest of abrasion. It appears flawed. Why is it not bonding better to the paint? What causes this and how can I prevent it from happening? Is this a defective varnish that can be removed? How would I remove it?

Candle Wax Protectant

Question asked 2019-06-22 15:39:13 ... Most recent comment 2019-06-24 08:40:03
Technical Art History Other Studio Tools and Tips Varnishes

​Hi All,

I use candle wax for make art and have been using resin as a sealant. However, it is super shiny and thick. Any suggestions on what I could use to prevent damage and something that is Uber heat heat resistant? Thanks so much and be well! 

Casein and casein/oil tempera techniques around 1900

Question asked 2019-06-23 06:28:50 ... Most recent comment 2019-06-23 23:01:14


I am currently examinating a wall painting form 1901, that was very probably painted using  casein as a binder. Apparently this medium became popular for the use to paint on the wall with artists who usually painted on canvas. Why did it become popular again and what does its popularity has to do with the industrial revolution? Are there manuals and recipes from arts schools from the end of the 19th century known, that are describing this technique for monumental wall painting in Europe and the US?

Thank you very much, your help is appreciated!

Cold Wax Medium

Question asked 2019-06-22 09:09:03 ... Most recent comment 2019-06-23 22:28:55

How long does it take for an application of cold wax medium atop a finished painting to fully cure, so that a second layer of medium can be appplied on top without affecting the first?  Or does the underlying medium stay indefinitely somewhat soluble when a new layer of medium (with some percentage of solvent in it's formulation) is added on top?  Are cold wax mediums that are soluble in mineral spirits (such as Renaissance wax) stronger than those soluble in OMS (Gamblin's cold wax medium); i.e. is the fact that whatever resin in the medium is soluble in a stronger solvent mean it contains a stronger resin?  Thanks, Koo Schadler

Percentage of resin in grinding medium

Question asked 2019-06-20 15:23:33 ... Most recent comment 2019-06-20 15:19:00
Drying Oils

​Dear Mitra,

Although I know that it can be confirmed or denied that the old masters used resins in their mediums I wish to use a bit in mine. 

Whats a healthy amount of Dammar Varnish to put into ones medium? 


Question asked 2019-06-17 12:26:52 ... Most recent comment 2019-06-18 18:19:41
Grounds / Priming Pigments

​The main ingredient in Chloreseptic (an oral analgesic) is phenol, which can act as a preservative or biocide, from what I understand.  I don't know what else the product contains. What do you think about using Chloreseptic in either pigment pastes or gesso to inhibit mold growth?


Koo Schadler

Are certian oils more fat than others ?

Question asked 2019-06-17 16:23:08 ... Most recent comment 2019-06-18 18:02:55
Drying Oils

​Dear Mitra,

It seems that everyone describes fat over lean as simply placing more oily layers over less oily layers.  But are certain oils in and of themselves more fatty than other ones if equal amounts are set out? For a example if I set out an equal amount of a polymerized linseed oil and refined linseed oil is one fattier than the other?  Since one was polymerized does this change its fat/lean state? 

Thank you,

Hector Hernandez

Dyed Canvas Question

Question asked 2019-06-18 14:21:00 ... Most recent comment 2019-06-18 17:20:07


I recently dyed canvas using acrylic paint. This is a process that I use fairly often. The canvas came out of the dye bath having a funny odor, I am wondering if you know of a solution to get rid of the smell, without messing up the canvas? Vinegar?

Making inkjest prints "archival quality"??

Question asked 2019-06-17 10:08:40 ... Most recent comment 2019-06-18 06:03:58
Art Conservation Topics Dyes Environment Ink Photo-Documentation / Digital Printing Pigments Varnishes

​I have studied the materials from Golden Paint regarding using thier MSA varnishes over inkjet prints for UV protection  and it appears that they provide significant protection against fading for dye and pigment based injet prints.

Can injet prints treated with these UV protective varnishes be sold as "archival quality prints"?  

Dammar resin in a painting medium

Question asked 2019-06-13 08:45:15 ... Most recent comment 2019-06-13 22:54:16
Paint Mediums

​ Hi! Is there a minimum amount of Dammar resin that can be safe as an ingredient in oil painting mediums?   It is well-known that large amounts are not acceptable. From my own experience I can say that nothing compares with mastic/dammar painting mediums when I produce/create the painting: blending, flowing, drying rate, tixothropy, etc... But in terms of conservation and durability the story is totally different.  For his recipe (the famous 1:1:5), Ralph Mayer calls for a 5-pound cut Dammar Varnish.  Do you think that 1 part Dammar Varnish in this recipe is excessive, moderate, acceptable? Can be reduce the amount of dammar varnish in this recipe to get an acceptable painting medium, in order to prevent yellowing, varnishing problems, cracking, etc...? Or the answer is simple: NEVER use! Thank you !

Clove Oil for slowing drying rate of oil paints

Question asked 2017-04-25 14:20:23 ... Most recent comment 2019-06-11 02:53:53
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?

Adhering fabric to plywood

Question asked 2019-06-06 09:57:17 ... Most recent comment 2019-06-06 14:39:31
Rigid Supports

​I've recently started adhering pre-primed canvas to cradled plywood rather than painting directly on the plywood. I seal the wood with shellac on all sides and then adhere the fabric with PVA glue. However, I have some leftover plywood panels from beforehand that I had prepared diffferently or started to use. All of the panels were sized with GAC100 and then either A) primed with oil primer but not used or B) primed with acrylci primer and then underpainted in oils. My question is whether in either of these cases it would be possible to glue fabric over the exiting structure.  I suspect the scenario A (the top layer is oil primer) would have enough tooth to provide emchancial adhesion but I'm less confident of the B scenario (the top layer is oil paint over gesso).  

Mixing Water Media

Question asked 2019-06-02 12:04:16 ... Most recent comment 2019-06-03 19:27:51
Acrylic Casein Egg Tempera Gouache Watercolor

To what degree can watercolor, gouache, casein, glue tempera, egg tempera and acrylic - all water media - be intermixed, or at least used to tint one another?

Koo Schadler

Acrylic, Oil painting Air Quality Comparisons

Question asked 2019-05-31 09:00:12 ... Most recent comment 2019-06-03 10:29:27
Oil Paint Studio Tools and Tips

​I wonder if there have been any studies comparing the air quality, when using acrylic paints versus oil paints without solvents. My oil painting class is treatened because of lack of ventilation.

Varnishing with a regalrez based varnish too soon.

Question asked 2019-05-19 21:24:29 ... Most recent comment 2019-05-31 18:12:24
Oil Paint Varnishes

​The general advice is to wait 6 - 12 months before varnishing an oil painting.
Specifically regarding regalrez based varnishes, Gamblin suggests that a painting can be varnished with Gamvar as soon as it is touch dry, which contradicts advice from George O'Hanlon and Virgil Elliot.

What I would like to know is, what are the consequences of varnishing too early with a regalrez based varnish?

Varnish suitable for both oil and acrylic

Question asked 2019-05-29 18:42:31 ... Most recent comment 2019-05-30 23:27:53
Acrylic Varnishes Oil Paint

​I often see artist wanting to leave raw canvas showing in their paiintings.
Recommendations for this are to use a GAC product from Golden, or a clear acrylic polymer as a barrier.

So if someone were to have a surface of both acrylic and oil, what varnish/s would you recommend that could be removed from both without damaging the paint?

George O'Hanlon recommended an isolating coat before the final varnish, but I imagine the isolating coat would eventually need to be removed as well at some point.

Ron Francis

Large amounts of oil for oil paints

Question asked 2019-05-28 02:23:33 ... Most recent comment 2019-05-29 11:15:19
Art Conservation Topics Drying Oils Oil Paint Paint Mediums Scientific Analysis Rigid Supports

Hello all,

I've done a couple of experimental paintings lately with a large amount of walnut oil added to tubed oil paints and mixed until the paint has the consistency of cream/thin yoghurt.

I have seen no wrinkling with the walnut oil (I expect there would be wrinkling with stand oil or plain linseed oil)

I am sure that the paint films will be less archival than using a minimum of oil, but if painted on a rigid (Dibond) surface would you expect that they would still last for decades, or fail within a few years?

One of the reasons I'm not sure is that I'm read that extenders and filler pigments like PW5 can make a paint film weaker, yet they are used a lot in student grade paints.


Polishing an egg tempera painting

Question asked 2019-05-08 17:19:48 ... Most recent comment 2019-05-24 23:03:02
Egg Tempera

Hello! and thank you for this wonderful forum!

Many ET painters find themselves painting smaller and smaller works but I am the opposite. My paintings tend to get larger and larger. I just completed an 8'x4' ET and it "only" took 2 years! Ordinarily I would polish my painting with a soft cloth: silk, flannel or T-shirt material has been recommended and I have not found much difference between them. Due to the large size, and some physical limitations, I am experimenting with power tools. I've tried a "polishing bonnet" attached to my corded electric drill but am interested in purchasing a dedicated buffer. A Dual Action Random Orbital Polisher  (DA) seems to be the safest option, in terms of not harming the surface,  but I don't want to invest in it unless I feel it will be more effective or safer than my drill buffer or hand polishing. The "bonnets" I am using now are what came with the conversion kit- one is lamb's wool and the other an unknown synthetic. If I get the DA there seem to be endless options in polishing pads. Of course they are meant for automotive polishing. I love traditional methods/ materials but am not one to scoff at high tech improvements. Perhaps the old saw about ET developing a gentle egg shell gloss will be proven a myth once more effective polishers are employed and a higher gloss will be achieved (not that I necessariy want that.) Obviously if I see any paint on my bonnet I'll know the machine is too aggressive or the paint surface inadequately polymerized. So far I have tried it on the edges of my monster ET panel and no paint has come up, nor have I achieved any more shine than with elbow grease. Hoping you might have some experience with this. Perhaps conservators use electric buffers with a variety of pads? If not my path would be clear: buy the DA and try different pads on castaway paintings or trial paintings and see what the effect is. Thanks much for your great work!

Lora Arbrador

CPVC in Tempera

Question asked 2019-05-14 10:42:38 ... Most recent comment 2019-05-22 08:49:15
Egg Tempera

My experience has been that a well-tempered egg tempera paint (good handling properties, consistent shine, etc.) has a CPVC of about equal parts yolk to pigment.  I've always puzzled at the greater variability, at times, of pigment to binder ratios in oil versus in tempera, which has much less variability in that regard - almost all colors temper well at equal parts yolk and pigment, with just a few minor variations (some lean, thirsty earth colors, like burnt umber and sienna, need a wee bit more yolk; fatter viridian needs a tiny bit less).  One would think that whatever variabilities in pigment to binder ratio exist in oil would transfer to tempera - but they seemingly don't. 

And while I've heard the terms "fat" and "lean" used to describe a pigment's need for more or less binder, what acutally determines if a color is fat or lean (and, back to my original question, why does that need seem to vary from one medium to another)?


Koo Schadler

Egg Tempera as Metalpoint Ground

Question asked 2019-05-14 10:10:46 ... Most recent comment 2019-05-20 10:55:33
Grounds / Priming Egg Tempera Drawing Materials

​Hello MITRA,

I've been playing with egg tempera as a ground for metalpoint.  If layered thinnly and allowed to cure egg tempera is, like casein, a good ground (due to its PVC); yet I rarely see tempera mentioned as a metalpoint ground.  Any thoughts?

Also, is egg tempera as vulnerble to hydrolysis as oil paints?  


Koo Schadler

oil painting in the aeroplane

Question asked 2019-05-15 14:04:02 ... Most recent comment 2019-05-17 10:47:12
Handling and Transportation

​Dear Mitra,

i was comissioned an oil painting that I will have to take with me from Europe to South America. This means at least two changes of airplane and a 13 hr long flight in between. The painting will be 90x100 cm. As it will be newly made and flexible when we fly, i assume there will be no problems with rolling it, as far as done correctly. I wonder if there is a save way of bringing a painting in an aeroplane, a way of packing it where it can be sent safely it with the checked baggage. Advice and tips will be much apreciated. 

Thank you!


Using a marble stone as a palette

Question asked 2019-05-11 21:28:28 ... Most recent comment 2019-05-13 10:47:19
Oil Paint

Before using a marble stone as a studio palette ( 16 x 22 inches), I wanted to check with you for any special preparatory treatments that may be required for the marble surface prior to oil painting.

I believe the marble top is older (resale store bargain purchase)  and possibly one made from a combination of marble powder and stones.

Your suggestions and ideas are always helpful.


WMO Oil paints and traditional oil paints

Question asked 2019-05-08 15:13:08 ... Most recent comment 2019-05-10 20:24:06
Oil Paint Solvents and Thinners

Hi all,

If I do a layer of a painting with WMO oil paints mixed with water as a solvent, and then I paint over the top with traditional oil paints (because of more pigment choices, etc..) will this cause an issue? Would the water remain trapped in the WMO paint layer, or will it evaporate through the traditional oil paint layer?

I have read that it takes a lot longer for all the water to actually evaporate out when using acrylics, so is the same the case for oil paints?

Are you aware of any issues with paintings done in a mix of WMO and normal oils in this manner?

Thank you,

Traditional drying oil - hard resin varnishes

Question asked 2019-05-05 15:19:41 ... Most recent comment 2019-05-09 19:13:48
Drying Oils Scientific Analysis Solvents and Thinners Varnishes Art Conservation Topics

Dear experts! I have several questions about traditional sandarac and copal drying oil-resin varnishes.

1. In various articles I encounter mentions of good preservation of such varnishes after hundreds of years, for example, in case of paintings by Carlo Crivelli or Orazio Gentileschi. Are those cases just coincidental exceptions or drying oil-hard resin varnishes age better than their cousins made with oil and colophony, larch balsam or mastic?

2. Is it absolutely necessary to heat sandarac or copal resins in oil to make a good varnish? Or maybe I could use an intermediate solvent to avoid extensive thermal treatment?

3. Could I use modern zirconium-calcium octoate drier additions instead of traditional lead linoleate? How much worse are such driers than lead-based ones in the long term?

4. How important is to use fresh Cypress or Juniper sap instead of dried and oxidised resin which is always sold in art supplies stores? In Da Vinci’s recipe use of fresh sap in spring is recommended.

5. Could I enhance ageing performance of such varnishes by adding Tinuvin 292 and 1130? Or maybe using other modern additives?

6. I’ve heard that new methods of old varnish removal gain popularity, such as laser ablation. Could I rely on such technologies for future conservation efforts of my paintings or I should care about varnish solubility and use Regalrez 1094 with Tinuvin 292 because they remain soluble despite their not so good appearance, scratch resistance and necessity to wait one year before varnishing?

Thank you.


Question asked 2019-05-07 12:28:08 ... Most recent comment 2019-05-09 12:38:12
Oil Paint


I'm having problems with underbound imprimatura since I upgraded to artist quality oils. I guess part of the "problem" is the higher pigmentation of my new oils. I can't seem to achieve a bound yet semi transparent layer of paint. I'm diluting burnt umber with mineral spirits. I've recently had the same problem with an opaque venetian red ground I layed out on another canvas. In that case I oiled out the entire canvas. I tried to do the same with the raw umber imprimatura, but in rubbing the oil I ended with a brown surface and my underlaying drawing completly lost.

Am I using to much solvent? How can I achieve a semi transparent imprimatura that is bound enough?

Thank you for your valuable advice!


Varnish or fixative for Prismacolor, and graphite

Question asked 2019-05-07 15:00:49 ... Most recent comment 2019-05-08 07:38:45
Pencil Varnishes Other Art Conservation Topics

I am doing large scale drawings/rubbings using prismacolor sticks in some and graphite in others. These are too large to frame -- some will never be covered (and will be rolled to ship and stored with glassine over top), others will be covered with a sheet of Plexi (offset from the surface)

I will break this into a two part question:

1) Prismacolor: I am concerned about lightfastness and wondered if there is a suitable spray or brushable varnish that can provide UV protection for the Prismacolor. I am only using the Level 1 and 2 lightfast colors. (If there is a better quality color pencil in stick form--please let me know. I have not been able to find much information)

2) Graphite: final fixative that will protect if the drawing is rolled or brushed against since there may not be any plexiglass?

Thanks very much.

rabbit skin glue

Question asked 2019-05-03 15:17:17 ... Most recent comment 2019-05-07 12:34:10
Animal Glue

​Hi, I just read somewhere that rabbit skin glue only smells when it has gone bad... Is this true? I had never heard it before, assumed the smell was normal. Now I worry that the glue I just sized some canvases with is bad.

Effects of ageing and conservation efforts on Renaissance egg tempera paintings

Question asked 2019-05-01 04:45:56 ... Most recent comment 2019-05-03 14:02:17
Art Conservation Topics Egg Tempera Scientific Analysis Oil Paint

Dear experts! I am an amateur painter interested in other’s works. When I look at portraits by Botticelli, I do not understand what do I see. My guess is that nowadays his paintings are very different from what was intended. So, I have several questions. For example, let’s consider his Portrait of a Young Man (Washington). 

1. What do I see at the edges of paint flakes divided by craquelure? I think that when the ground layer cracked, separate flakes slightly curved and their edges raised. Next, paint near edges of flakes was abraded during handling and cleaning of the painting, upper layers of paint were stripped. So at the edges near minuscule cracks I see lower paint layers. Is this correct?

2. How transitions between light and dark parts of the face were applied, particularly at the nose and cheek? I see darker spots of paint without clearly defined edges. They appear to be spatially oriented as if they are parts of longer brush strokes. What causes this interrupted appearance? Are they a result of paint abrasion? Or his panel was grounded with some texture and we see an effect similar to watercolour granulation on rough paper?

3. Opening the image in GIMP and using a CIELch colour picker reveals complex variations of hues, particularly at skin areas. How such variability was achieved? In my understanding of egg tempera technique, a painter mixes pigments in raw state, grinds them on a stone with binder and puts resulting paints in dishes. Without mixing on a palette since tempera dries fast. I have several guesses, but what is correct? Perhaps, many pigment mixtures were composed in raw state? Or he composed just a few pigment mixtures and applied them in several very thin layers of varying density? Or he used tempera grassa which dries slower and mixed it on a palette like oil paints? Or the painting was heavily overpainted during many conservation efforts and we see a result of using slightly different pigment mixtures by restorers? This is certainly the case near some major cracks and scratches, but to what extent other areas are overpainted? 

4. Is there a darker layer of paint under light areas of the skin? Or lighter parts were painted straight on a white ground with some sketch made with dark coloured lines? I guess I see darker underlayer in a lower left corner of his neck near the fur collar.

5. What happened with some hairs of the left eyebrow (model’s right eyebrow)? I see crisp lines of dark coloured paint but a couple of lines are very dim. Were they abraded? Or they are parts of preliminary drawing covered by subsequent paint layers?

6. The overall skin color is very yellow, about 1/3 more yellow than a real skin color of a Caucasian man could potentially be - I am judging by CIELab colour coordinates and limits given in an article by A. Chardon «Skin colour typology and suntanning pathways». I wonder is this a result of binder or varnish yellowing? Or an artistic choice to make it look more saturated?

7. The color of his fancy hat is puzzling. Too orange for an ordinary cinnabar. I guess its color is an effect of particle size - somewhere I’ve heard that very finely ground cinnabar turns almost to carrot-orange. Or is it a result of fine glaze applied atop of cinnabar? Or another pigment was used too, like realgar or orpiment? 

I would be grateful if you’ll share your opinions and point me towards research papers to read. Thank you.


Question asked 2019-04-26 20:41:17 ... Most recent comment 2019-05-02 10:21:09
Egg Tempera Health and Safety

Hello everyone. I have a question concerning  health issues as I am going to begin doing egg tempera.  Seeing that we handle pigments I think it is preferable to wear a protection mask so as not to breathe or inhale the toxicity of the pigment. Could you give me some advice on that I can anticipate? Thank you.

Minor warping of Baltic Birch plywood with traditional RSG gesso.

Question asked 2019-05-01 09:37:26 ... Most recent comment 2019-05-01 12:33:35
Animal Glue Egg Tempera Rigid Supports Grounds / Priming

Another panel question!

 I recently purchased a 5'x5' sheet of ¾" Baltic birch plywood and cut into 30"x30" pieces for use as panels.

For two of these pieces:

I applied a coat of RSG size, muslin adhered with RSG, and 8 layers of traditional gesso on BOTH SIDES of the panel. Save my application of cloth to both sides of the panel, my method generally followed instructions for gessoing detailed in Daniel V Thompson and Koo Schadler books. About 3 days of drying and the panels have warped a small amount in one direction. If I set a rigid rule from edge to edge of the panel, I can see about 1.5-2mm space between the center of the panel and the rule. Hanging the panel on the wall, the warp is barely noticeable, but I wonder, is this evidence of even greater instability of my panels in the near future? Or, if I'm willing to accept the current warp, could I paint them (with egg tempera), shellac the back, with any confidence?

I've had extremely bad luck workign on plywood and also custom made panels in terms of warping at the gesso stage at this scale of 30"+

Still learning a lot from this forum, thank you,


Adhering Paper to Aluminum Sheet

Question asked 2019-04-23 13:27:58 ... Most recent comment 2019-04-27 19:46:22
Rigid Supports

​I would like to adhere a 30 x 44" sheet of  paper to a 1/4" sheet of aluminum 31" x 45" so that I can achieve a 1/2" aluminum border around the paper that will have  a machine-routed, 'mirror-finished' polished edge, similar to a glass beveled edge. I was told by Talas Conservation Materials that Bevo 371 drymount film would be the best canidate for a hot press, given its low temperature adherance rating at 150 degrees farenheit, and therefore not warping the sheet metal in the heat press. I am not certain how to prepare the main body of aluminum underneath the paper ...questioning if the metal will oxidize the paper sometime down the road or if it will remain relatively stable in typical gallery/museum envirnoments? I have found nothing negative attibutable to oxidation of aluminum as a rigid mounting surface that might affect the paper. So I am actually seeking best advice on mounting the paper to raw aluminum sheet given the use of the Bevo 371 film by itself. The aluminum is typically what I would purchase from an industrial supplier of  1/4" sheet aluminum. Can you help?


Using only oil as medium

Question asked 2018-01-31 18:43:27 ... Most recent comment 2019-04-25 08:30:27
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.)?

alkyd oil ground

Question asked 2019-04-23 04:32:22 ... Most recent comment 2019-04-24 17:05:26
Alkyd Animal Glue Flexible Supports Grounds / Priming Oil Paint

​Dear MITRA team,

I've read through a lot of the existing threads but I do still have some question on the sizing/priming of flexible supports. 

Regarding rabbit skin glue, I understand that most artists have decided against it's use by now. But I would still like to know if conservationists unanimously advice against the use of RSG on flexible supports (like they have done with, for instance, the use of Zinc Oxide) or if it is more a matter of preference and which risks one might be willing to take with the material. I'm also not so clear on how do disadvantages of using RSG compare those of using PVA glue or acrylic size. I do understand the problems with cracking, but I'm still interested in using RSG for stiffness. I have to say, another reasons for me considering it is somewhat romantic. I like the idea of using a material that has been used and regarded as the best option for centuries. I'm aware of the faultiness of this logic though. So, please help! 

My second question would be is it would be ok to use an alkyd based ground (I'm thinking titanium white, marble dust or similar, alkyd binder and maybe some oil) on top of the RSG or PVA, and under oil painting. I would do this mainly for time convenience (drying time). I wonder if succesive coats of oil would adhere well to the alkyd ground, that results quite glossy. 

Finally, I would like to know how many coats of glue and how many of ground you would recomend for best results on flexible support. 

Thank you so much for your great work! 


Tradition Gesso to Fiberglass

Question asked 2019-04-21 15:07:33 ... Most recent comment 2019-04-22 23:13:52
Animal Glue Rigid Supports Sizes and Adhesives Art Conservation Topics Egg Tempera

​One more panel and traditional gesso question:
I was recently given a sample of honeycomb aluminum faced with fiberglass. I applied 4 coats of traditional gesso and after a week of dry time did a cross-hatch adhesion test. The adhesion seemed good. Anyone have experience with these materials? I don't know how fiberglass registers wil best practices but it seems like a potential solution for egg tempera paintings at a larger scale. Thanks in advance! - eli

Adhering Muslin or Linen to ACM for use with Traditional Gesso and Egg Tempera

Question asked 2019-04-21 12:03:40 ... Most recent comment 2019-04-22 17:46:37
Animal Glue Acrylic Art Conservation Topics Egg Tempera Grounds / Priming Rigid Supports Sizes and Adhesives

I'm looking for more panel advice, in this case to adhere Muslin or Linen to Aluminum Coposite Material. In my case Honeycomb aluminum for use with traditional gesso and egg tempera. I've heard BEVA works well but I hope to use at a scale of 30"x30" to 50"x50" and I don't have a heat press. Any thoughts? Or PVA could work: I've used Gamblin PVA to size linen in the past but that seems too watery for adhereing cloth to the ACM. Is there a good PVA Gel or glue? Finally, I've used Acrylic gel medium to glue paper to wood panels, could Acrylic gel adhere cloth to ACM? Thank you! - Eli

A Composite Surface Made from Joined Pieces of Linen

Question asked 2019-04-19 16:42:13 ... Most recent comment 2019-04-21 00:47:28
Flexible Supports


I am researching ways to sew together individual pieces of linen (like a patchwork quilt) to be stretched over a rectangular stretcher. Eventually, I would like to do this at a very large scale, but for the moment I am just making studies. I am currently working with Claessens oil primed linen #13, which I have on hand. I wrote to Claessens to inquire about the weight of the thread they use in weaving this particular product, and they said it was nm 40. I have ordered a linen thread that is two-ply and advertised as 40 (though I wonder if there might be a difference because I am purchasing it in the US and we don't use metric?). My thinking is that matching the thread weight/strength as best I can will help keep the seams from slowly destroying the linen squares under tension over time. A friend suggested that using a sewing machine will help keep the seams even, and thus will spread the tension more evenly across the matrix than a hand-stitched textile surface would.  

I wonder if anyone on this forum has suggestions for me (aside from the obvious "don't do this," lol!) Do you think linen is a good choice? The person I corresponded with from Claessens suggested that a synthetic fiber might be best. Linen has historical resonance that I appreciate, and it is strong, but I'd be willing to work with polyester if that seems more adapted to my purpose. I work in oil paint and use a simple gamsol/linseed oil medium. Do you think the Claessens pre-primed oil primed linen is a reasonable choice here, or do any of you think I would be better off with a different sort of priming under my paint layer? (Ideally I would like to paint on it and then cut it up and sew it together, not sew it and prime the resulting matrix as one surface). It seemed to me that a commercially made product would be likely to be more consistent than something I primed myself. If there is anyone out there who knows about large-scale textile display (quilts and rugs and the like) are there technologies I should consider for supporting this textile painting-quilt hybrid from the back? Any references you could give me would be much appreciated! 

Thank you!

Krista Schoening


Using newsprint in mixed media work.

Question asked 2019-04-17 02:52:27 ... Most recent comment 2019-04-21 00:38:57

I make mixed media work with a lot of paper elements, mostly drawing papers which I paint watercolor. However, I also use newsprint which I glue onto areas of acrylic paint and rub some of it away, and then paint that in watercolor. It bothers me knowing that newsprint yellows over time, and although changes to my work and the watercolor paint I later paint this paper has not had any color shift, ​I would like to chose a better alternative. I need a paper that is thin, short fibered, that can absorbed water-based paint. Nothing caught my attention at the art supply store, except for layout bond.

Generally I seal these areas using a product called Polycrylic.

Using heat to remove dents in stretched canvases

Question asked 2019-04-19 18:28:43 ... Most recent comment 2019-04-19 19:38:09
Drying Oils Flexible Supports Oil Paint

​Regarding an oil painting on stretched canvas, I have heard a suggestion that one can use an iron on a low heat on the reverse side to flatten dents or folds.
Elsewhere, it was said that heat will damage oil paint.
I'm pretty sure that I have read that applying heat is an acceptible technique from a qualified source, but can't remember where.

Csn you please give you views on this.
(Assume that the paint layer is thin, flat and smooth.)

Canvas Stretching and Desirable Tension of Canvas

Question asked 2019-04-19 15:48:06 ... Most recent comment 2019-04-19 19:32:31
Oil Paint

How much tension should be placed on the canvas when stretched over wood bars and is it necessary to secure the stretcher bars together prior to stretching the canvas?


My reason for asking is prompted by my method of stretching the canvas. I use a Fredrix style 22 cotton canvas that is unprimed at 7 oz. and primed at 11.5 oz. , plus an additional four coats of quality Gesso is applied to the stretched canvas.

Tightness of the canvas allows for a "hollow" sound when thumbing the face side and there is some slight tension pull shown at most staples.

Will the canvas tension impact the oils after several years?

Is it advisable to secure the corners of the stretching bars or let the canvas maintain a good corner square? I have personally seen both methods used and am concerned if there is an advantage over one method.

Patrick McGuire

Regarding Best Ratio for using Zinc White/Titanium White Combination

Question asked 2019-04-16 15:06:51 ... Most recent comment 2019-04-19 15:48:58
Oil Paint

Several authors have recommended using a combination of Zinc White and Titanium White for use in landscape paintings especially for imagery of clouds; ratios of varying amounts including one part Titanium to 3 parts Zinc White. Book sources ranged from 1974 up to the present and written by established painters.

I have personally used one product that offers a premade mixture of the two whites. However, I would greatly like to learn of using various ratios of Zinc White combined with Titanium White to achieve sky and tinting effects in landscape paintings along with the potential risk of Zinc White having a possible long term change.

Your ideas and suggestions are appreciated.


Patrick McGuire

Tucson, AZ

Adhering Copper to Panel for Oil Paint

Question asked 2019-04-17 11:10:17 ... Most recent comment 2019-04-17 11:55:14
Grounds / Priming Sizes and Adhesives Rigid Supports Oil Paint

​I would like to adhere 3 ml - 5ml copper sheets to a panel surface to paint. What is the best practice for adhering copper this thick to panel? Is a different thickness recommended? Also, what is the best practice for preparing the copper to receive oil paint?  

Layering different water-based media

Question asked 2019-04-16 19:06:16 ... Most recent comment 2019-04-17 11:46:13
Acrylic Gouache Ink Watercolor

From a conservation point of view, would it be a problem to layer acrylics, gouache, watercolors, inks, etc. over each other? For example, would a layer sandwich of:

  1. Watercolor
  2. Acrylic
  3. Gouache
  4. Acrylic

(or some other combination) be a problem? I'd imagine that, once dry, the acrylic layers would keep everything below set.

ACM - RSG gesso - will it stick?

Question asked 2019-04-16 22:45:10 ... Most recent comment 2019-04-17 10:14:17
Animal Glue Egg Tempera Grounds / Priming Sizes and Adhesives Rigid Supports

Does traditional RSG gesso adhere well to anything besides wood? I'm struggling to find a good solution for egg tempera painting at somewhat larger than traditional scales, about 30" square. I've had very mixed results in terms of warping panels when applying traditional gesso to high grade plywood of various thicknesses (both cradled and not) at a scale of about 30" square. I adhere a layer of cotton muslin to the face of plywood panels, also with RSG, to avoid checking, and also gesso both sides of the panels. My new fantasy is that if there really are adhesion issues with RSG gesso to materials like aluminum, fiberglass, etc what if linen or other fabric was glued to one of these materials?  The fabric could enjoy an industrial bond or a BEVA bond to the ACM or whatever kind of stable support and then the traditional gesso could enjoy a bond to the openness of the fabric… thoughts? (I've found one fine art manufacturer who suggests the surface of their ACM panels will take hide glue just fine, even without the interlayer of fabric, but they don't sell panels at a scale large enough for my purposes.) Thank you for thinking about this with me!​

Sealing Wood Panels with Shellac for egg tempera painting (Will RSG adhere to shellac?)

Question asked 2019-03-15 13:06:25 ... Most recent comment 2019-04-17 02:58:48
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

Acrylic Isolation Coat

Question asked 2019-01-29 18:43:38 ... Most recent comment 2019-04-17 02:43:56

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.

Flashe paint preservation in the jar

Question asked 2019-04-14 09:08:29 ... Most recent comment 2019-04-16 18:53:12

​I have many colors of Lefranc & Bourgeois Flashe vinyl paint, and am not using them quickly. I've noticed that they tend to harden in the jar, though I'm careful to keep the jar threads and lids clean and screwed on tight. I don't want to add water and potentially create mold, and am wondering if anyone knows a good vehicle to thin this paint and keep it usable longer.

Question regarding a Final Oiling Out and Temperature Effects on oil

Question asked 2019-04-16 11:07:04 ... Most recent comment 2019-04-16 14:23:04
Oil Paint

An observation was made on two types of finished oil paintings: stretched canvas and canvas panel on paper hardboard, that reveal some type of impact heat may have on the thin layer of walnut oil rubbed over the final painting before varnishing.

After the first week of drying time, a nice oily shine appeared on the canvas. At the end of the third week under much higher temperatures (85 to 100 degrees F ), the surface now showed a visible dry and flat appearance as if no walnut oil was applied.

Each painting used a quality canvas, received four (4) additional coats of gesso and quality oil paints were used.

Did heat change the appearance of the walnut oil and it remains on the surface, but not in a shinny wet appearance?

Did the heat evaporate the walnut oil product?

Did the higher temperatures allow for the oil to be absorbed into the painting, requiring additional coats of walnut oil prior to the application of varnish?

Your thought would be most appreciated!

Patrick McGuire

Tucson, AZ

Oil Paint over Acrylic Molding Paste

Question asked 2019-04-13 17:03:52 ... Most recent comment 2019-04-15 11:04:41
Oil Paint Paint Mediums


I want to start exploring impasto techniques and more sculptural techniques with oil paint, and I'm trying to learn the best ways to do that without my painting falling apart. I like to paint on wooden panels so I was wondering if I could use a product like Golden's molding paste to build up a texture, and then paint over it? What steps would I need to take to do this properly? My current plan would be to size the panel with GAC 100 x2 layers, then 2 layers of acrylic gesso, then the molding paste on top. Does the type of molding paste I choose matter?

I also bought an impasto medium from W&N to try out, but thick oil paint layers can take a while to dry which is why I wanted to explore other options. I don't want a case where my paint never dries properly.

Intermixing Acrylic Paint

Question asked 2019-04-12 15:27:11 ... Most recent comment 2019-04-13 07:22:00

​What are the risks of intermixing brands of acrylic paint; for example, a jar of Liquitex white tinted with a color from Golden or Dick Blick?


Koo Schadler

Dibond Vs Plywood panel

Question asked 2019-04-10 10:18:39 ... Most recent comment 2019-04-10 11:54:08
Acrylic Art Conservation Topics Rigid Supports


I usually paint small and use either dibond or plywood panels. I am about to start a larger piece (in acrylics): 60x100cm and I wonder which support should be better. Dibond is lighter but isn't it more fragile and ready to bend? Heavy outdoor plywood is obviously very heavy but looks stronger to me. What do you think? Thank you.

Best regards,

Thomas Ehretsmann (France)


Question asked 2019-04-08 15:36:08 ... Most recent comment 2019-04-08 18:24:48

​I am writing about imprimatura and have 2 questions.

Can an imprimatura tone a ground ANDan underdrawing or should it read ground OR underdrawing?

I know that an imprimatura can be a translucent glaze of paint, can it also be a colored size or colored varnish?

Gilding on Paper

Question asked 2019-04-03 15:16:04 ... Most recent comment 2019-04-04 12:54:12

​What is the best practice for gilding on paper? 

Waterbased varnish for oil

Question asked 2019-04-01 15:34:25 ... Most recent comment 2019-04-01 23:01:09
Acrylic Drying Oils Varnishes Oil Paint


I have recently come across a waterbased varnish (Acrylic resin 80%; stabilisers - according to the manufacturer's website) that is recommended as a product for varnishing oil or acrylic paintings. I have never seen a waterbased acrylic dispersion varnish recommended for use on oil paintings before.

I am curious as to your viewpoints on this. Specifically regarding adhesion and ease of removal.

Many thanks.

Spray applying Gamvar matte varnish

Question asked 2019-03-25 22:39:44 ... Most recent comment 2019-03-31 21:14:25
Varnishes Oil Paint

​Hello all,

I have been experimenting with Gamvar matte varnish to even out the alternatly dull and shiny areas in my oil paintings, which have large flields of flat color over a smooth surface. The brushstrokes from the varnish application are showing up when the varnish dries and it's distracting to the work. I understand that matte Gamvar is the trickiest to apply and am experimenting with different techniques. In the meantime, I asked a Gamlin product specialist on the phone about spray-applying the matte Gamvar, which they said required a proper respirator and ventilation, but is a common practice for conservators. Has anyone attempted this and can you offer tips before I give it a try? Would this require an air compressor, or can I use a Preval sprayer? Finally, is there a company or conservator anyone can reccomend in NYC that I might be able to hire to do this for me? I reached out to some prominent NYC art materials and finishing companies but so far am coming up dry. Thank you in advance!


Metalpoint Fixative

Question asked 2019-03-29 11:52:21 ... Most recent comment 2019-03-31 19:41:30
Drawing Materials Varnishes

I want to explore the idea of applying fixative or varnish to a metalpoint drawing.  My reasons are:

1.  I combine metalpoint with fairly developed egg tempera painting on panel (see attached as an example: metalpoint lettering & egg tempera rabbit on Golden black gesso); the work, to me, appears too "removed" from the viewer when framed under glass - so I'm looking for a way to frame without glass that will nevertheless give some protection to the surface; i.e. a light spray coating of B-72, followed by a wax medium.

2. In my metalpoint experiments (described in an earlier MITRA post) some metals and grounds, when exposed to a lot of sulfur, faded or completely vanished.  I understand the lesson: trying too rapidly to speed up tarnishing can be detrimental to a drawing. However, it also points to the potential vulnerability of metalpoint lines; the insecurity of their attachment to a support.  I realize there are many centuries-old metalpoint drawings in good shape, so I don't mean to say it's not a durable medium; only that it also has the potential to not hold up well. Additionally, I've heard two artists comment that drawings on "Plike" paper tend to "fade" or lose their metalmarks, but many metalpoint artists love working on Plike.  Would a fixative be a good idea for those people who opt for the convenience of a pre-made, less-than-ideal metalpoint paper?  

I understand that a fixative (depending on how sealing or heavily applied) may slow or completely stop the tarnishing effect, but what if an artist doesn't mind or actually wants to deter tarnishing?   Would a light coating of fixative still allow for tarnishing?  

In short, if fixatives are suitable for other forms of drawing, are they suitable for metalpoint as well?  

Tho' I'm interested in subjective preferences, I primarily want to hear the objective, technical pros and cons.



Exposed White or Clear Gesso

Question asked 2019-03-29 17:49:06 ... Most recent comment 2019-03-30 17:58:20
Varnishes Oil Paint Grounds / Priming

​​Is there any technical reason why it would NOT be a good idea to leave parts of a white acrylic dispersion (gesso) or clear matte acrylic dispersion (matte medium) ground exposed in the final painting, which would ultimately be varnished? This would be oil painting. I'm also wondering if a varnish, i.e. Galkyd, would look different over the oil paint areas vs the exposed gesso areas. Thank you for any thoughts.

Polyester Canvas

Question asked 2019-03-24 17:53:34 ... Most recent comment 2019-03-25 16:40:35
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?

Checking wood

Question asked 2019-03-25 11:33:22 ... Most recent comment 2019-03-25 13:31:03

​Hello! I've an acryllic painting on a piece of  1 inch standard plywood (smooth on top) that is beginning to check. The wood was sanded, then a primer was put on top, and then the acryllic paint was applied. The painting was begun in December 2018. Is there a way to prevent or stop the checking with the painting already done?

Tacks or staples?

Question asked 2019-03-24 17:21:16 ... Most recent comment 2019-03-24 19:53:39
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?

Making paint "long"

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.


Vandlized Painting

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?

Whiting for Gesso

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

Damir Pusic

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.

Cradling large, rigid, synthetic supports

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?

Oil paint becoming transparent over time.

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.

Alizarin Orange lightfastness confusion

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.

Preserving kraft paper, construction paper, and other non-archival papers

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?

archival adhesive wood and paper

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.  

Safflower oil on rigid panels

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?  

Sealing Panel Edges

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?  



oil based spray 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!

Seeking a way for painting to be fun again: ok to mix walnut alkyd with stand oil and OMS?

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!

Inner Glow panels

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.

Mounting canvas and paper to wood panels

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

archival affixitive?

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?

titanium-lead white paint mix

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.

limestone and plant glue

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

Another Mt. Athos Icon Question

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

Cedar Wood

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?


Rabbit Skin Glue

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

Dipropylene glycol as an oil paint medium

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?

Alkyds and varnish

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. 

Old acrylic painting on canvas

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

How to frame a painting on panel without using screws?

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.


Relative Humidity specifics

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!

Polyethylene foam as a frame-padding material for wood panels?

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? 



Water gilding over oil gilding

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 

ABS PLASTIC-Acrylonitrile Butadiene Styrene as Painting Panel

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."

Golden Black Gesso and Egg Tempera

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 

Humidity in Studios in Apartments

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

Stone or Mineral paper as painting surface

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.

Fresco Colors

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

Any issues with using pure Lamp Black (PBk6) with oils?

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,

Mixing Acrylic Mediums

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

Plywood support with traditional gesso

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.

Regalrez 1094 varnsihes

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?

Water Miscible Oil Paint

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

Spots on Oil Painting

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

Canvas not adhering to panel

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

Paper stuck to Acrylic Paint Film

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!  :)

Ralph Mayer's book...

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.

Removing excess graphite with a kneadable eraser.

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? 

How can I Flatten out a wavy / buckled drawing paper?

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.  


Metalpoint Experiments

Question asked 2018-11-01 12:15:10 ... Most recent comment 2018-12-11 15:18:44
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, 



Gouache and Watercolor on Drawing paper?

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

Oil seepage to surface of white oil paint

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?

Framing fresh egg tempera paintings behind glass

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

Gilding Oil Paintings

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

Gouache techniques

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

Sound and Toxin Free Oil Painting

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

how much of which varnish?

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,


What solvent removes old damar?

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.  

sealing of charcoal on bristol

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.

Difference between various odorless/low odor mineral spirits

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.



Amber Varnish and Medium

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.

Slippery nature of walnut oil

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?


Oil paint adhesion to acrylic primer

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! 

Bitumen/Asphaltum/Gilsonite Nbk6 pigment in oil paint

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?

Magnesium Sterate

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.

how to protect color of plants pressed on paper from UV ?

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

Robert Vickery

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

PW7 Zinc Sulphide

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.

oil paint stick recipe

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


Affixed labels with fish glue

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.

Final Varnish over Retouch Varnish?

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  

Oil painting mediums

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 

Gilding 19th century in Portugal

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!


Acrylic Varnish info

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

Varnishing the Edges

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. 

Adhesive properties of sun thickened oil

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?

Egg Tempera Glazing Medium

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 

prints and oils

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?

Alkyd and Glitter

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. 

egon schiele

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

Saponified Wax?

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?

Priming Wood/Canvas Panels

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.  

Isolating Egg Tempera

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?



Pastel substrate-Dibond, Alumalite

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,


Tackifier / plasticiser for carnauba wax based encaustic medium

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? 

Lead Point

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

Oil paint on Alumacomp surface

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?

Collage Adhesive for Oil Painting

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?​

Regalrez 1126 as a final varnish

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?


Mystery Pigments

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



The best type of aluminum

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)).

Protection of back of paper/canvas

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:

Why does fabric need to be sized but cotton rag paper doesn't?

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.

Preparing An Ideal Rigid Support

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

Clove oil vapour test - FYI

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.


Durable paint films

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..

Musty Smell on Canvas

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

Alternative Oil Based Ground Canvas Primers

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

Sealing the back of canvases

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

Contaminants in rags/paper towels.

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? 

Metalpoint Questions

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 



black patina on Rodin bronzes

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!

Oil paint storage

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,


medium/oiling out/varnish

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...

Primer soaking up oil paint

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?


Non-Toxic Solvent Product

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!

Oil Paint Seep to Rear of Canvas- Conservation

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!

Mistakenly mixed oils and acrylics, can I save my painting?

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.

"Non-Absorbant Gesso"

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.

Pigments in modern time.

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.

Maxfield Parrish Painting Needs Conservation

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


Alkyd and 1-shot enamel

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!

Collaging inkjet print to acrylic painting...

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?

Uv protection over oil, outdoors

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! 

How to frame silverpoint

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?


Studio safety

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.                                                                                 

Water-Miscible Underpainting

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!

Oleoresinous varnishes polymerized with oil

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.

Storing oil paintings with corrugated cardboard sheets between painted surfaces

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.


Need information - priming of linen canvas

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.  


Wood turner and cabinetmaker

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.  

Encaustic over Watercolor?

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!

Collaging into oil paint

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. 

Oils over Acrylic Underpainting

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!

Sealing Gold leaf

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.

Venentian turpentine and stand oil

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!

Permanent cotton fabric sealer (ground,gesso,size) for permanent adherence to magic smooth epoxy.

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.



refractive index of Oil paint samples by manufacturer, does it exist?

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.

Archivality of polymer-covered acidic paper

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.

How do I seal acidic adhesive?

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

Panel Bracing

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.

Archival qualities of oil based ink on paper for printmaking

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. 

Best White for Imprimatura

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.

Wyeth and Ink Underdrawings

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

Green for Oil Thinner - Non-toxic solvent?

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.

Lamp black - 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,

Plywood panels

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?   

How can I have slate veneer tested?

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

Will copper corrode even if sealed with Incralac?

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.


Spit Polish - amylase powder

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?

Standing desk

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!



Sizing/priming the reverse of the canvas

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?

Digital Printing on Acetate

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?

Sticky/stringy paint without levelling

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. 

Arches Oil paper mounting, repainting old paintings

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

Unprimed linen canvas 8x8 warp and weft

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? 

Linen used in the 19th century

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?


Sleeping in the Studio w/ Drying Oil Paintings.

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) 

Acrylic isolation coat and varnish query

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! :)


(Imitation) goldleaf and acrylic medium

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?​

Rigid Supports

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

Synthetic sable brushes

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


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?


Manganese Oxide Blue (YlnMn)

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)?

Protecting Back of Wood-Based Panels

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?



Mounting finished painting on linen onto panel

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?  



Double Layer Canvas vs Hardboard Support

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.

Alla Prima question

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.


The "fat over lean" principle in alkyd painting

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?

Masking tape archivability issues

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?

Archival Polyester Films

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.

Linen stretching and sizing best practices?

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?

After thirteen years, I want to finish an oil painting.

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).


Half Oil Ground

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

Rubbing or Grain Alcohol as a solvent

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!

Lessening Dust Exposure to Drying Paint

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...?

Industrial Canvases Sizing and Priming-How they do that?

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?

Gum-oil emulsion medium

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

Coldpressed linseed verses alkali refined linseed

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?

Casein as very diluted underpainting for oil painting?

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). 

Paper Repair

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.​

Egg Tempera Conference in Munich

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

Cadmiums in oil paintings, conservation.

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.


oxidation of metalpoints

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

cracked painting

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

Can you mix casein emulsion with tubed watercolors?

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.

Safe Layering with Oils

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.

Oil Paint Safety

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

House acrylic paint interaction with artist acrylic ground/paint

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?

New peptide free linseed oil

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:

Do I need a Lead Based Ground to Build a Strong Painting?

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.

how do you fix charcoal on top of oil paint?

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?

Creating a Stable Fabric Substrate

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?

Oil Paint Not Bonding?

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!

Resource: Historical textiles

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!

Best support currently available for painters

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!

Oil painting not drying

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!

Adhesive for Latex

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.

Cotton v linen

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?

Acceptable types of papers for painting

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?

vinyl as binder

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.


Frixion pens for underpainting?

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,

Mounting Linen onto ACM

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. 

Longevity of vinyl paints

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?

Cleaning of oil brushes: non-drying oils and other questions

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?

Solvent toxicity in oil painting

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)

Fat over lean and solvents

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?

storage of oil painting in dark for 8 years

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?

Polymerized oil as a final varnish

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,


Pinholes in Gesso, Golden's Flow Aid

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

Lead-White production

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

linen on hardboard

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?​

longevity of oil mediums over acrylic

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

Combined oil mediums

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. 

Lead-White acetate

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 ?

Gilding With Oil Painting

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?

sealing hardboard with shellac

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. 

Sun Bleaching Oils

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?

Gluing primed polyester canvas to board

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.

"vehicle" used in making oil and acrylic paint

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

Inhaling paint fumes

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?​

Old mold stains on unfinished canvas. Safe to resume painting?

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.


Merry Christmas and Thank you!

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!!​

oil and acrylic paints

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.

Moisture or greasy film on duralar with Acylic ink painting

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.

Acrylic Painting on Metal ( from the “ground” or “ primer” up)

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

Can I use soapstone dust to make gesso?

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?

Durability of Watercolors vs Oils

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.

Modern secco technique

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.

Cardboard as a surface for acrylic

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.

Graphite into Oil Paint

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!

Pigment Oil Ratio

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?


Stapled Corners of Stretcher Bars

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.

Scanning electron microscope image of sunken in oil paint

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.

Gamblin PVA Size

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? 

Tips for working with catagory II and III lightfast-rated pigments

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!


Acylic "Gesso" drying time

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.

Oil Paint on Shellac

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! 

calcium carbonate

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 ,


Walnut Alkyd Medium

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? 

oil paint medium

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.

Painting thin long lines in oil

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.

Oleo resin mediums

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.

Linen vs cotton for large scale

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?


Ampersand Museum Clayboard for Scratchboard

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)?​

Sealing the back of Hardbord with GAC

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?

Some questions about working on copper

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?



Isolating varnish

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.

Watercolors without Glass?

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.

New digital technology uses in conservation of art.

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.

The colours in "Girl with a Pearl Earring"

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!

Need for flexible paint layers on rigid supports?

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.  

Oil or acrylic dispersion primers for best adhesion on rigid supports?

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.

Several inquiries into Painting on Paper, and Oil Paper

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.

How useful are early 20th C books on art materials?

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.

Henry Ossawa Tanner Painting Techniques

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.



Charcoal and oil how to "fix"

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. 

Lapis Lazuli extraction - Fra Angelino natural ultramarine recipe

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

Painting Light to Dark

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. 🍂

Andrew Wyeth's Ground

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

Dispersants & Egg Tempera

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?  

use of 4F pumice to create tooth in acrylic primers

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.

pros and cons of using sized, cotton wc paper for oils

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.

Ok to use acrylic primer under lead oil primer?

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! 

Does sanding the size reduce its functionality?

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?  

Mounting copper supports

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.

Varnishing over ink on oils

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?  

Backing larger canvases

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.


mounting oil studies on paper onto dibond

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.

Stable Instability. Pouring Oils..

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...


Resin in Medium

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 pa