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Old 03-08-2010, 07:23 PM
Nilesh Nilesh is offline
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Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

This raises some very interesting points:

Although it is generally believed that it is acceptable to paint in oils over acrylic gesso, it has been stated in several painting textbooks such as "The Painter's Handbook" that it is unwise to paint in oils over acrylic gesso because—unlike time-tested alternatives such as rabbit skin glue—the oil paint will eventually delaminate from the acrylic gesso surface. This effect may not make itself manifest for several decades and then mostly affecting thick impasto. The cause for this problem is the inability of oil paint to establish both physical and chemical bonds with the acrylic base. Applied to a canvas that has been primed with rabbit-skin glue, oil paint is able to penetrate the ground (which is porous, unlike acrylic gesso) and establish a permanent bond, both chemical and physical. Manufacturers of commercially sold, pre-gessoed canvases deny that delamination takes place. However, curators in the Smithsonian Museum are not permitted to use acrylic gesso under oil paint, precisely because of the delamination problem.

Soy-based gesso, is a low emitting bio-based gesso made from recycled soy content. Soy gesso is made with new bio-based dispersion technology that uses a soy ester with a modified soy-vegetable oil acrylic. The surface is similar to acrylic gesso, but is not a solid acrylic. Soy gesso is made using a thin film of a modified acrylic and the soy ester. The penetration and adhesion of the soy ester to the substrate and the thin film of modified acrylic may have advantages in creating a surface that allows a physical bond between the gesso and the oil paint. In addition, the thinner modified acrylic film is less resistant to cracking than a solid acrylic gesso.
(--from the Wikipedia article on gesso)


Any other thoughts and information about these issues, and about soy gessoes, are welcomed.












Last edited by Nilesh : 03-08-2010 at 07:37 PM.
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Old 03-08-2010, 08:19 PM
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WFMartin WFMartin is offline
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

Quote:
The penetration and adhesion of the soy ester to the substrate and the thin film of modified acrylic may have advantages in creating a surface that allows a physical bond between the gesso and the oil paint. In addition, the thinner modified acrylic film is less resistant to cracking than a solid acrylic gesso.

I think before I became eager to use it, I'd like to see some proof of this "may have advantages" portion.

I believe that most of the problems encountered with painting oil on "gesso" is that there are many gesso products that are not much different in their composition than acrylic white paint. That, then, becomes a problem with the marketing, and the people who are convinced to buy these "gessos" that do not do the job correctly. That tends to give the concept of using "acrylic primer" a bad rap, when I don't believe it to be.

Those gessos (really acrylic "primers") whose ingredients include appropriate materials are not subject to the same adhering problems with oil paint that the ones made so similar to acrylic paint are. And, the primers made with the appropriate materials can be easily sanded, allowing even further, physical bonding between the oil paint, and the primer surface.

One needs a primer whose surface provides a bit of "tooth" for the oil paint to adhere to it properly, and many acrylic primers don't provide that. If more of us would concentrate upon buying the appropriate "stuff" (all art materials included), and avoid buying the inappropriate "stuff," the manufacturers would quit selling the inappropriate material, and life in oil painting would continue to improve, instead of sending us searching for the appropriate materials, which are becoming increasingly difficult to obtain.

I'd like to see some proof for the claims of this soy material before becoming overly enthusiastic with buying it. Sounds like another man-made "global warming" to me.

Just my opinions.
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Old 03-08-2010, 08:36 PM
Nilesh Nilesh is offline
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

Yes, I am still a bit skeptical about this one. The wording is a bit suspect, and it may be that the manufacturer of the soy gesso is involved in writing the Wiki article. It sounds a bit too similar to ad copy or product promotion to me.

But what about the adhesion issue? What about the Smithsonian?

The point about acrylic manufacturers glossing over the potential problems may also be a legitimate one.

Are there other ways of ensuring adhesion (or making double-sure that no problems arose somewhere down the line, in the course of the decades)?

What about extra-rough or extra-tooth gessoes that would provide more mechanical bonding?

How legitimate a concern is the adhesion?

I wouldn't be at all surprised if there were some long-term adhesion issues using oils (especially thick, impasto oils) over a very smoothly sanded, eggshell-finish acrylic gesso.

What about using some of the other gesso-like products, like light modeling paste, which is very absorbent? Might some of these other products provide some extra adhesion?
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Old 03-08-2010, 09:11 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

I'm curious ...

Like Bill, I'm skeptical about some of the claims in the statement.

Just who is making these claims? The only manufacturer I can find is Marshall Carbee, http://www.carbeesoygesso.com . Nowhere on the site, however, do I find other, authoritative commentary. So I have to ask, did Mr. Carbee write the information on the wikipedia page??

I'm all for earth-friendly products, and this one may be everything Mr. Carbee claims, but I would like to read other views on the product.

As for other parts of his statement:

Rabbit skin glue is primarily a barrier, not specifically a ground or a primer, which is applied on top of the RSG. Yes, there are paintings directly on top of RSG, but that is not usual practice.

The claim that curators at the Smithsonian aren't allowed to use acrylic gesso under oil paint is also confusing to me. Curators curate -- it is conservators who work with restoring paintings. Conservation practices would likely not allow use of acrylics because these people are working with already-established oil-based paintings, and in that instance adhesion would be a real concern. I'm certain they would not be allowed to use soy gesso, either. Now if curators or conservators are making their own paintings, start to finish, any of them might very will choose to work on an acrylic dispersion ground, but that's a different matter entirely.

Thanks for this information. While skeptical, I'll try to keep an open mind about soy gesso, just that I would like more information. Wouldn't it be great to hear from actual conservators? My hunch, though, is that it will take some time to reach any useful conclusions.
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Last edited by rroberts : 03-08-2010 at 09:14 PM.
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Old 03-08-2010, 09:53 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

"The wording is a bit suspect, and it may be that the manufacturer of the soy gesso is involved in writing the Wiki article."

Ya think, huh?

There was a similar thread posted a couple months ago, either here on WC or over at Rational Painting, by some hopeful artist, wanting very much for the soy priming to be "the thing". As Robert mentioned, the Carbee product was the one in question, and as the specifics came out, the interest dissipated.

Yes, it sounds like a manufacturer is using Wiki for their own product endorsement. And, as far as I know, Carbee is the only maker (blender) of this product.

Something to keep in mind: if there were widespread adhesion problems with acrylic primers, we've had nearly 70 years to hear about them. So far, I don't know any documented problems with properly prepared canvases using acrylic priming.
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Old 03-08-2010, 10:35 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

I believe that I've seen more "evidence" (even if a bit questionable in its nature) that Liquin causes delamination of oil paint, than I have that acrylic primer (the "good" stuff) causes oil paint to delaminate, but artists still use Liquin for everything but pouring it on their breakfast cereal.

I believe that is is wise to keep in mind that conservators usually have two ulterior motives, when they recommend things to us artists, or ask us artists to avoid certain things. First, without paintings falling apart, they'd be out of work. And second, when they do have to repair work that is falling apart, they want it to be easy for them to fix. I believe artists should at least consider those two points, when they take the words of conservators as being advisable.

I will most likely continue to use the quality acrylic primer until, like most, sound, oil-painting-related materials, it becomes extinct. As I've mentioned, I believe in seeking out the "good" acrylic primer, applying many coats thinly, and sanding with 150-grit sandpaper, not polishing with 300- or 600-grit paper. That more coarse paper provides a really good tooth for the surface.

Over that, I apply two, very thin, flat coats of oil paint, to bond with, and size the surface of the acrylic primer, allowing it to dry, before I apply any "image" paint. A truly beautiful surface for applying a first layer of image, oil paint.

I don't envision my risking any delamination of oil paint with my materials, and my methods. Perhaps I am missing something, but I'm not quite ready to apply "soy gesso" just yet.
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Last edited by WFMartin : 03-08-2010 at 10:51 PM.
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Old 03-09-2010, 06:27 AM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

Sooo the writer of that most reliable wikipedia article is against this, uh, newfangled, un-time-tested acrylic primer stuff but gosh this absolutely brand-new (ahem, untested) soy stuff made by one manufacturer should be great!

That doesn't sound biased at all.

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Old 03-09-2010, 06:35 AM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

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Originally Posted by CareyG
Sooo the writer of that most reliable wikipedia article is against this, uh, newfangled, un-time-tested acrylic primer stuff but gosh this absolutely brand-new (ahem, untested) soy stuff made by one manufacturer should be great!

That doesn't sound biased at all.

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Old 03-09-2010, 09:05 AM
dcorc dcorc is offline
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

It's entertaining to note that the only two contributions made on the entirety of wikipedia by that user were first to add the paragraph on soy-based gesso:
http://en.wikipedia.org/w/index.php?...ldid=291976713

and then to slightly amend it.

http://en.wikipedia.org/w/index.php?...ldid=294984754

Hmm....
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Old 03-09-2010, 10:50 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

I basically agree with Bill's recommended process. An acrylic primer, thin application, two coats, light sanding with rough grit sand paper, followed by two coats of an oil primer. The sanding of any surface raises "tooth" that allows 3 d adhesion of one surface to another.

The only questions I have are about how well the acrylic primer may actually seal the panel. This in turn raises the question of what panel or surface one is using. There are products available that according to the manufacturers seal woods like cedar and redwood from any danger of natural wood chemicals or tannins or glues floating thru to the surface of the finished paint.

The other question is whether acrylic and oil primers establish any chemical bond, or is mainly a physical bond from sanding or from particles in the acrylic primer intended to provide bond for a surface paint?

IOW, if a sealer, or primer/sealer bonds to a panel, can an oil top coat actually bond to the acrylic primer sealer?
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Old 03-14-2010, 01:16 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

As a trained sceptic, it's important for me to look past any claims made by a manufacturer who would be financially motivated to make them. On the other hand, I also have to be careful not to stand too close to those who want to dismiss it.

A soy based gesso sounds reasonable to me, and worth investigating, if not nesessarily a perfect replacement for acrylic grounds. I've had enough first hand negative experience with acrylic primers to be unhappy with using them for oils and to keep looking for options.

Soy paints and adhesives are nothing new, and I imagine a soy gesso similar to one made with hide glue would work quite well. Acrylic mediums also make a very good sizing material, as does hide glue, but my own tests with starches has shown they don't offer a very good barrier against oil penetration. I haven't specifically tested soy protein this way, but I suspect it would fault to the same degree. If the soy primer would require sizing with a different material then it's less than ideal compared to the other alternatives.

My understanding to the cause for claims of adhesion problems between acrylic and oil paint lies mostly with what may be in the paint itself, particularly if it contains metalic soaps of zinc or aluminum, which is not always present. There are other factors as well, such as how the acrylic ground is made, what the support is, environment exposure, how the work has been cared for, and a bond that is based more on texture than a chemical compatibility. Many variables, and as artists we don't always know exactly what we're using, which is the real problem.
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Old 03-14-2010, 01:50 PM
dcorc dcorc is offline
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

Quote:
I haven't specifically tested soy protein this way, but I suspect it would fault to the same degree.

I doubt that its using soy protein - sounds like its derived from soybean oil

See http://www.carbeesoygesso.com/msds4.html

Quote:
Proprietary Soy Ester-Alkyd Emulsion Mixture ....This product contains a non-hazardous mixture of a modified alkyd-soy ester emulsion.


Dave
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Old 03-14-2010, 05:05 PM
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Re: Soy (Rather than Acrylic) Gessoes to Ensure Long-term Adhesion of Oil Paints?

Quote:
Originally Posted by dcorc
I doubt that its using soy protein - sounds like its derived from soybean oil...

I wondered about that too, but then I read: "Wash Requirements: Wash with soap and water" which made me think otherwise.

They sound like they're pushing the "green" aspect to an extreme, which is all fine and dandy, but I'm more concerned about function. Also their statements like "We made the best artist gesso ever made." Uh... come on now. I'm still curious about it, nonetheless.
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