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Richard P
03-04-2019, 11:15 AM
This is a truly excellent article recently posted by GOLDEN:
https://www.justpaint.org/on-the-yellowing-of-oils/

RomanB
03-04-2019, 12:02 PM
Very interesting, thank you for the link!

Brian Firth
03-04-2019, 04:34 PM
What do you know, water washing doesn't seem to do much. Who could have predicted that! :lol:

sarahsands
03-04-2019, 05:15 PM
What do you know, water washing doesn't seem to do much. Who could have predicted that! :lol:

The one thing I would share - although it was not a part of this data set - the water washed oils do appear to dry faster when cast on their own, so the process might have advantages in removing tocopherols - naturally occurring antioxidants that retard the initiation of oxidation. And researches like Leslie Carlyle, in recreating historical lead whites, did note that water washed oils gave a noticeably different feel to the paint. Of course, that was with lead and involved other factors not included here. But so far it is true we have not seen signs of less yellowing. But then so far everything seems to be bunching up - poppy, walnut, safflower, etc - and it might be that formulation has as much to do with how much any particular paint yellows than the oil. Certainly more to investigate and we want to keep an open mind.

Brian Firth
03-04-2019, 06:12 PM
The one thing I would share - although it was not a part of this data set - the water washed oils do appear to dry faster when cast on their own, so the process might have advantages in removing tocopherols - naturally occurring antioxidants that retard the initiation of oxidation. And researches like Leslie Carlyle, in recreating historical lead whites, did note that water washed oils gave a noticeably different feel to the paint. Of course, that was with lead and involved other factors not included here. But so far it is true we have not seen signs of less yellowing. But then so far everything seems to be bunching up - poppy, walnut, safflower, etc - and it might be that formulation has as much to do with how much any particular paint yellows than the oil. Certainly more to investigate and we want to keep an open mind.
Hi Sarah,

I have read that water washing does raise the acid levels, and in my experience with Natural Pigments Pale Grinders high acid ARLO it also seems to dry quicker, so I thought that may play a role. Do you know if acidity effects drying rate? I was under the impression that it does. Also, all alkali refined oils are water washed in the refining process aren't they?

My biggest gripe for all the claims for water washed oils is that they are very hard, if not impossible, to quantify and very subtle at best, and to me bears the hallmarks of pseudoscience with a helping of confirmation bias. Of course, in my subjective experience I could not see any difference in handling and I was able to confirm no enhanced resistance to yellowing in my experiments with water washing oils. I can hardly justify recommend the massive waste of oil and time that occurs during water washing. That, and the water washing prophets main miraculous claim is, above all else, no yellowing! Which ain't true :cat: Or maybe I am just a tad cynical in my older years :smug:

ronsu18
03-04-2019, 07:42 PM
i'm so surprised over the beeswax but, of course, shouldn't be. can't help hoping somewhere along the line ascorbic acid could prove the definite, commercially viable answer since different antioxidants work best in groups, and E and C belong. oh and add selenium. there's something heartwarming in the way we just need to understand nature no matter what we want to do well.

Harold Roth
03-05-2019, 05:40 AM
I think this article was excellent also. For me it confirmed my choice of walnut and poppy oil. I do use washed walnut oil from Art Treehouse, which I tried because of the idea of faster drying. Don't know if it's faster drying--my paintings dry fast enough for me--but IME the washed oil is more slippery than regular walnut oil. It feels more like poppy. Which is a yes for me.

sidbledsoe
03-05-2019, 08:22 AM
Yellowing gets more attention that anything else in oil paint I think.
I used to be more curious than concerned about yellowing, and I did a bunch of testing which ultimately led to my firm conclusion that is has all been done, all is known that needs to be known, and most importantly, that the off the hook concern about it is really much ado about nothing.
The very worst yellowing paint in a forced yellowing test (not real life painting) I have ever seen was a white made with pure safflower oil, but of course, ordinary light exposure cleared it completely too.

contumacious
03-05-2019, 05:53 PM
I was disappointed to see that they did not include a comparison of all the same oils used in the test, but with some alkyd resin included at varied percentages.

sarahsands
03-05-2019, 06:58 PM
I was disappointed to see that they did not include a comparison of all the same oils used in the test, but with some alkyd resin included at varied percentages.

We absolutely agree that is an important thing to test and hope to include mediums - especially alkyds - in future rounds, along with flake white, other additives like aluminum stearate, and to the extent possible, environmental conditions such as humidity and temperature. So see this as a first entry, which we will update at 5 years and then every fifth year after that, with additional rounds coming up behind.

sarahsands
03-05-2019, 07:05 PM
I can't help hoping somewhere along the line ascorbic acid could prove the definite, commercially viable answer since different antioxidants work best in groups, and E and C belong. oh and add selenium. there's something heartwarming in the way we just need to understand nature no matter what we want to do well.

Oh, I don't think you want to add in antioxidants! As healthy as they are for us, they adversely impact the ability of drying oils to oxidize, which after all is what you need them to do in order to form a film.

contumacious
03-05-2019, 07:36 PM
We absolutely agree that is an important thing to test and hope to include mediums - especially alkyds - in future rounds, along with flake white, other additives like aluminum stearate, and to the extent possible, environmental conditions such as humidity and temperature. So see this as a first entry, which we will update at 5 years and then every fifth year after that, with additional rounds coming up behind.

Great! Thanks for all the work done so far. I am looking forward to the future testing.

sarahsands
03-05-2019, 09:51 PM
Hi Sarah,

I have read that water washing does raise the acid levels, and in my experience with Natural Pigments Pale Grinders high acid ARLO it also seems to dry quicker, so I thought that may play a role. Do you know if acidity effects drying rate? I was under the impression that it does. Also, all alkali refined oils are water washed in the refining process aren't they?

Hi Brian. I would be interested in any reference you can point to claiming that water washing raises the acid level. At least in the references, I could find it points in the opposite direction since acid value is related to free fatty acids and water washing specifically claims to reduce the amount of free fatty acids in the oil. At the same time water washed linseed oil is still likely higher in acid value than alkali-refined linseed oil at its lowest. As for acid value's role in drying time, I think other factors play a bigger role, such as the fatty acid profiles or the number of tocopherols (natural anti-oxidants). From another angle, one measure of an oils reactivity, a good predictor of drying speed, is listed as identical for low, medium, and high acid value oils - the high acid being Pale Grinders. And yes, alkali-refined oils are water-washed during their processing. We wrote a fairly good description of the process here:

https://www.justpaint.org/the-process-of-alkali-refining-linseed-oil/

My biggest gripe for all the claims for water washed oils is that they are very hard, if not impossible, to quantify and very subtle at best, and to me bears the hallmarks of pseudoscience with a helping of confirmation bias. Of course, in my subjective experience I could not see any difference in handling and I was able to confirm no enhanced resistance to yellowing in my experiments with water washing oils. I can hardly justify recommend the massive waste of oil and time that occurs during water washing. That, and the water washing prophets main miraculous claim is, above all else, no yellowing! Which ain't true :cat: Or maybe I am just a tad cynical in my older years :smug:

Not cynical - I think just thinking critically and being properly skeptical. We tested the water washing because, if nothing else, it IS rooted in historical processes and so gives one point of comparison and, as you noted, it has a following and we wanted to take those claims at face value and see if they held true. As for the differences in handling, the sources for that comes from research headed up by Leslie Carlyle. Unfortunately, a lot of the papers covering that work are not easily available. If you can try to find the following:

"A multi-analytical approach to studying binding media in oil paintings: Characterization of differently pre-treated linseed oil by DE-MS, TG and GC/MS" (https://novaresearch.unl.pt/en/publications/a-multi-analytical-approach-to-studying-binding-media-in-oil-pain)

You might try searching for it in quotes to see if you can find a source. Otherwise, the following chapter from van den Berg's PhD thesis, Analytical chemical studies on traditional oil paints

The effects of traditional processing methods of linseed oil on the composition of its triacylglycerols (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.607.36&rep=rep1&type=pdf)

covers very similar if not identical territory, although with a lot more technical detail than you might need or want.

Gigalot
03-06-2019, 02:19 AM
Eggshell white calcium carbonate test after a year into living room condition.

1 Eggshell in 50% Alkyd +50% refined Linseed oil
2 Eggshell white in pure sun bleached Linseed oil
3 the same + 20% Maries titanium white acrylic paint
4 the same + 10% Master Class acrylic-styrene varnish

and you can see also thin eggshell white glaze layer on top of dioxazine violet tint.

Brian Firth
03-07-2019, 09:17 PM
Hi Brian. I would be interested in any reference you can point to claiming that water washing raises the acid level. At least in the references, I could find it points in the opposite direction since acid value is related to free fatty acids and water washing specifically claims to reduce the amount of free fatty acids in the oil. At the same time water washed linseed oil is still likely higher in acid value than alkali-refined linseed oil at its lowest. As for acid value's role in drying time, I think other factors play a bigger role, such as the fatty acid profiles or the number of tocopherols (natural anti-oxidants). From another angle, one measure of an oils reactivity, a good predictor of drying speed, is listed as identical for low, medium, and high acid value oils - the high acid being Pale Grinders. And yes, alkali-refined oils are water-washed during their processing. We wrote a fairly good description of the process here:

https://www.justpaint.org/the-process-of-alkali-refining-linseed-oil/


I found the reference in this document from the The Department of Art Conservation at the University of Delaware's Materials Information and Technical Resources for Artists forum.

https://www.artcons.udel.edu/mitra/Documents/MITRA_Mediums_and_Additives.pdf

Specifically the last sentence of this section:

* Water-Washed Oil: Any drying oil that is washed in water to remove mucilage and water soluble impurities (these impurities were called “the foot” in older literature). This was done by placing the oil, water, and any additives in a large jar. The whole was shaken and mixed and allowed to set until the oil, and water separated, some recommended placing the container in the sun. This was repeated many times until the foot separates and can be found directly above the water and below the oil. The clean oil was then siphoned off. Oils purified by this method are made more acidic than they were before the process. 



Not that this is by any means definitive, and I am not sure if it is an official document now that I look at it. It's the only reference for water washing increasing acid levels I have come across. I wasn't sure anyways so I appreciate your clarification and information on the factors of drying in oils. You would think of all processes, alkali refining would "strip" all the tocopherols and make it the fastest drying.


Not cynical - I think just thinking critically and being properly skeptical. We tested the water washing because, if nothing else, it IS rooted in historical processes and so gives one point of comparison and, as you noted, it has a following and we wanted to take those claims at face value and see if they held true. As for the differences in handling, the sources for that comes from research headed up by Leslie Carlyle. Unfortunately, a lot of the papers covering that work are not easily available. If you can try to find the following:

"A multi-analytical approach to studying binding media in oil paintings: Characterization of differently pre-treated linseed oil by DE-MS, TG and GC/MS" (https://novaresearch.unl.pt/en/publications/a-multi-analytical-approach-to-studying-binding-media-in-oil-pain)

You might try searching for it in quotes to see if you can find a source. Otherwise, the following chapter from van den Berg's PhD thesis, Analytical chemical studies on traditional oil paints

The effects of traditional processing methods of linseed oil on the composition of its triacylglycerols (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.607.36&rep=rep1&type=pdf)

covers very similar if not identical territory, although with a lot more technical detail than you might need or want.

And I certainly appreciate the thoroughness of your research in exploring all avenues and aspects from a objective standpoint! I think you guys are doing great work and the fact that you are so generously sharing it with the world it is to be applauded. :clap: Thanks for the links as well I will certainly check them out.

sarahsands
03-07-2019, 10:57 PM
I found the reference in this document from the The Department of Art Conservation at the University of Delaware's Materials Information and Technical Resources for Artists forum.
Thanks for that. I know the folks there, so let me reach out to them and see - who knows, maybe we will both learn something!

The one thing I can think of is that when drying oils undergo hydrolysis a lot of free acids are produced because water beaks the ester bonds that join the fatty acids to the glycerol molecule, releasing the fatty acids from their moorings. However, most of what I have read about hydrolysis relates to dried oil films, but perhaps that is happening here as well. Let me think it through and check on some things tomorrow, or over the weekend.
You would think of all processes, alkali refining would "strip" all the tocopherols and make it the fastest drying.
Looking at some quick online accessible sources,

https://aocs.onlinelibrary.wiley.com/doi/pdf/10.1007/BF02661798

https://www.researchgate.net/publication/227170379_Total_and_individual_tocopherol_contents_of_sunflower_oil_at_different_steps_of_refining

https://tinyurl.com/y3j92x5b

it appears that about 30-50% of the tocopherols are refined out. They play something of a beneficial role for big producers as they are essentially anti-oxidants, thus helping to preserve and stabilize the finished product over time. Keep in mind none of the above references are specifically focused on linseed but I think the general percentage of removal will likely be comparable. I will see if I can find more specific info.

And I certainly appreciate the thoroughness of your research in exploring all avenues and aspects from a objective standpoint! I think you guys are doing great work and the fact that you are so generously sharing it with the world it is to be applauded. :clap: Thanks for the links as well I will certainly check them out.
It's our pleasure Brian. And we will definitely continue researching and are committed to publishing and sharing the results as they come in.

Gigalot
03-08-2019, 02:56 AM
I use refined oil to prepare my sun-bleached oil. Actually, I can make sun oil, that dries much faster and too much polymerized than I like to have. It can dry like Alkyd after several hours. I do not like such material and, therefore I do less polymerized and less oxidized linseed oil than people here want to have.
I need two days of hidden drying time for comfortable linseed oil usage. However, sun light still reduce contaminants content and reduce yellowing of sun-bleached oil.

Brian Firth
03-08-2019, 08:16 PM
I use refined oil to prepare my sun-bleached oil. Actually, I can make sun oil, that dries much faster and too much polymerized than I like to have. It can dry like Alkyd after several hours. I do not like such material and, therefore I do less polymerized and less oxidized linseed oil than people here want to have.
I need two days of hidden drying time for comfortable linseed oil usage. However, sun light still reduce contaminants content and reduce yellowing of sun-bleached oil.


Alex, I have speculated to myself that the most useful part of all the water washing of oils is the sunlight exposure that is part of the process. I have an example in this photo of you organic flaxseed oil I left in a jar on my shelf for about a year. I picked it up one day and noticed that just from normal room lighting in my studio it had lightened considerably and clarified. I poured some of the original oil that was still in the lightproof container on the top slowly and you can see a clear difference. They are the exact same oil, juts one got some light on a shelf in a jar and probably partially polymerized. No water washing needed! Just patience.

Gigalot
03-09-2019, 02:26 AM
Refined oil is already water washed and treated with bleaching earth. The only thing I need to do is to bleach small amount of contaminants with sun light illumination and atmospheric oxygen exposition. Linseed oil is the best oil for painting. After bleaching it became even more fine. :)

Michael Lion
03-10-2019, 09:47 PM
This article is great stuff. It show that a lot of internet prognosticators who say that anything in oil paint besides oil and pigment ruins the paint, they are totally wrong. Paint needs fillers, stabilizers and emulsifiers to keep the pigment and oil from separating as the paint dries.

This explains why brands like Gamblin that have a lot of oil-pigment separation (presumably because they believe in the philosophy of not using too much emulsifiers and stabilizers) yellow badly compared to brands where the oil and pigment stay together.

Gigalot
03-11-2019, 12:20 PM
Conclusion

Our results have shown that yellowing is closely related to the extent of drying. In our opinion, yel-lowing of drying oils is mainly due to contaminants. At temperatures up to 60°C, parameters increasing the oxidation rate—such as higher tem¬perature or presence of a drier—only increase the yellowing rate but have no influence on the yellow¬ing tendency. For temperatures below 40°C, when reactions of fatty acid chains are slowed down, reactions with contaminants appear to be favoured and yellowing tendency is higher.
Differences in degrees of yellowing for different oils may be attributed to various concentrations of contaminants or various sorts of contaminants. Comparative studies of yellowing are then very dif-ficult to interpret, even with comparable drying extents. For a given oil, yellowing will increase until there are no more contaminants or until the complete drying of the oil sample is achieved, with no more radicals formed in the film. Since yellow¬ing is also significant in poppyseed oil containing less than 1% of linolenic acid, the role generally attributed to this polyunsaturated acid in the for¬mation of yellowing products appears to be unfounded.
Solutions to avoid yellowing of oil-based paints appear to be very difficult to achieve. Only extremely purified oils or synthetic compounds may lead to colourless films, and an elevated drying tem¬perature would be required to reduce interactions with contaminants.
However, it must be noted that yellowing, although unaesthetic, is not a significant criterion of physical degradation because it involves only weak concentrations of contaminants and leaves the net¬work unaffected. Even more, because it is a mea¬surement of the extent of drying, it may be considered as a proof of the hardness of the film that is completely dried. Yellowing must therefore be considered as an unavoidable characteristic of drying oils and this must be kept in mind by users.

sidbledsoe
03-11-2019, 12:43 PM
Conclusion

In our opinion, yellowing of drying oils is mainly due to contaminants.

so if the yellowing is mainly due to contaminants, and yellowing is proportional to the unsaturated fatty acid profile, then the amount of unsaturated fatty acids should also be mainly due to the level of contaminants, that is a surely a new one on me.

sarahsands
03-11-2019, 05:46 PM
Conclusion

Our results have shown that yellowing is closely related to the extent of drying. In our opinion, yel-lowing of drying oils is mainly due to contaminants. At temperatures up to 60°C, parameters increasing the oxidation rate—such as higher tem¬perature or presence of a drier—only increase the yellowing rate but have no influence on the yellow¬ing tendency. For temperatures below 40°C, when reactions of fatty acid chains are slowed down, reactions with contaminants appear to be favoured and yellowing tendency is higher.
Differences in degrees of yellowing for different oils may be attributed to various concentrations of contaminants or various sorts of contaminants. Comparative studies of yellowing are then very dif-ficult to interpret, even with comparable drying extents. For a given oil, yellowing will increase until there are no more contaminants or until the complete drying of the oil sample is achieved, with no more radicals formed in the film. Since yellow¬ing is also significant in poppyseed oil containing less than 1% of linolenic acid, the role generally attributed to this polyunsaturated acid in the for¬mation of yellowing products appears to be unfounded.
Solutions to avoid yellowing of oil-based paints appear to be very difficult to achieve. Only extremely purified oils or synthetic compounds may lead to colourless films, and an elevated drying tem¬perature would be required to reduce interactions with contaminants.
However, it must be noted that yellowing, although unaesthetic, is not a significant criterion of physical degradation because it involves only weak concentrations of contaminants and leaves the net¬work unaffected. Even more, because it is a mea¬surement of the extent of drying, it may be considered as a proof of the hardness of the film that is completely dried. Yellowing must therefore be considered as an unavoidable characteristic of drying oils and this must be kept in mind by users.

I am familiar with the above conclusion from the article "Yellowing of Oil-Based Paints" by J Mallégol back in 2001. The thesis remains provocative but then others have taken chemically pure trilinolenin and it yellowed even worse than alkali refined oil. So something more than contamination would seem to be at play.

See "Autooxidization and Yellowing of Methyl Linolenate" by Rajkumar Kumarathsan

Rakoff et a/.13 studied the influence of linolenate on yellowing and other film properties of linseed derived paints. In their study, four vehicles namely alkali refined linseed oil (ARLSO), a decolourized alkali refined linseed oil (DLSO), pure trilinolenin (Ln3) and bleached hydrogenated linseed oil (BHLSO) were chosen, and had linolenate content from 0-100%. The trilinolenin which had 100% linolenate dried faster (Table 1) and yellowed much more than the other paints (Table 2). The bleached hydrogenated linseed oil paint which had no linolenate and unsaturation, was white after the same period of time and required weeks to dry. The alkali refined linseed oil paint yellowed faster than the decolourized linseed oil paint. This difference is due to the increased linolenate content in the alkali refined linseed oil paint.


http://www.wetcanvas.com/Community/images/11-Mar-2019/74844-Color_of_experimental_paints.JPG



So, not sure......but would be interesting to pursue further.

RomanB
03-11-2019, 06:23 PM
I am familiar with the above conclusion from the article "Yellowing of Oil-Based Paints" by J Mallégol back in 2001. The thesis remains provocative but then others have taken chemically pure trilinolenin and it yellowed even worse than alkali refined oil. So something more than contamination would seem to be at play.

See "Autooxidization and Yellowing of Methyl Linolenate" by Rajkumar Kumarathsan



So, not sure......but would be interesting to pursue further.

He cites Privett's article (https://doi.org/10.1007/BF02634999), where experimental section opens with the following passage:

"The methyl linoleate used in this investigation was obtained from the Hormel Foundation and was prepared by debromination of pure tetrabromstearic acid. Its iodine value was 173.0 (theoretical 172.4), and it contained less than 0.1% conjugated material. Samples of methyl linoleate prepared in an identical manner were previously found by Brown (6) to contain no less than 90% of the cis, cis isomer. The balance presumably consisted primarily of the cis, trans and trans, cis isomers of methyl 9,12 octadecadienoate."

Link to Brown's work is just: "Brown, J. B., pre-publication communication."

So, I doubt that their results are reliable. They used too complicated way of synthesis without serious testing of resulting products.

sarahsands
03-12-2019, 06:03 AM
He cites Privett's article (https://doi.org/10.1007/BF02634999), where experimental section opens with the following passage:

"The methyl linoleate used in this investigation was obtained from the Hormel Foundation and was prepared by debromination of pure tetrabromstearic acid. Its iodine value was 173.0 (theoretical 172.4), and it contained less than 0.1% conjugated material. Samples of methyl linoleate prepared in an identical manner were previously found by Brown (6) to contain no less than 90% of the cis, cis isomer. The balance presumably consisted primarily of the cis, trans and trans, cis isomers of methyl 9,12 octadecadienoate."

Link to Brown's work is just: "Brown, J. B., pre-publication communication."

So, I doubt that their results are reliable. They used too complicated way of synthesis without serious testing of resulting products.

Thanks Roman. Point taken in terms of Privett's article, but the section I quoted was citing Rakoff, Gast, and Thomas's, Yellowing and Other Film Properties of Linseed-derived Paints Influenced by Linoleate Content", so unrelated to Privett. Plus, even if the methyl linoleate was not 100% pure, one would still expect it to be freer from contaminants than the alkali refined oil, no? Or am I missing something?

In any case, I do think the article by Mallégol is interesting and worth following up on, and many of their points were in line with our own findings - such as the fact that poppy and linseed oil ultimately appear to yellow similarly, and the lack of impact on yellowing from driers.

All good stuff.

Gigalot
03-13-2019, 06:34 AM
After reading many articles, I did my own experiments with linseed oil yellowing
effect. I have most effective result with adding Zinc White and also mineral spirit acrylic varnishes into my paints. Zinc White improve drying properties and therefore reduce yellowing, while acrylic polymer will dilute linseed oil. That decrease yellowing reaction between oil molecules.
I found that natural resin can turns brown with the presence of cobalt drier. It might be better to avoid dammar addition into paint or medium with cobalt content. I use MSA acrylic instead.

Michael Lion
03-13-2019, 08:21 AM
I found that natural resin can turns brown with the presence of cobalt drier. It might be better to avoid dammar addition into paint or medium with cobalt content. I use MSA acrylic instead.

I believe that natural resins, either because they were used as a varnish or were mixed in with the paint, is the major contributor to the poor appearance of old oil paintings in museums.

JCannon
03-14-2019, 01:15 AM
"I believe that natural resins, either because they were used as a varnish or were mixed in with the paint, is the major contributor to the poor appearance of old oil paintings in museums"
Apologies for bringing up a point I've made several times before, but it is a fact that the Pre-Raphs used lots of copal, and their works still look magnificently vibrant. That said, I don't trust dammar. Neither do I trust completely alkyds and cobalt drier.

Alex: "mineral spirit acrylic varnishes"? You introduce this into the paint itself? I thought that this produce was intended purely as a final varnish.

I'm not as paranoid as some others are when it comes to Zinc, but surely this would have an impact on hue or value...?

Gigalot
03-14-2019, 03:41 AM
Alex: "mineral spirit acrylic varnishes"? You introduce this into the paint itself? I thought that this produce was intended purely as a final varnish.

I'm not as paranoid as some others are when it comes to Zinc, but surely this would have an impact on hue or value...?
Several manufacturers recommended to use their solvent borne acrylic varnishes as oil painting mediums or they added acrylic into regular linseed oil mixtures. I preffer to add 5%-10% of Newskaya Palitra acrylic varnish into my painting medium on the place of alkyds or dammar.

I use Zinc White at a low concentration to bleach Cobalt violet light, Phthalo blue paints e.t.c 1% of pure Zinc White (Titanium free) paint addition or so.

JCannon
03-14-2019, 02:07 PM
I don't know about the Nevskaya Palitra acrylic varnish. The only supplier of Mineral Spirit Acrylic Varnish in the US is Golden, and they definitely recommend against using the stuff as anything but a final varnish.

See here. (https://www.justpaint.org/why-oil-painting-over-msa-or-archival-varnish-is-not-recommended/)

Granted, this article relates to tests of oil paint applied over a thin layer of varnish. They did not test an oil paint/varnish admixture. But the photos are still plenty scary.

I shall retreat to the traditional stance of keeping the worlds of acrylics and oil painting separate, with the exception of acrylic gesso, which has proven itself over the years.

Gigalot
03-14-2019, 02:16 PM
I don't know about the Nevskaya Palitra acrylic varnish. The only supplier of Mineral Spirit Acrylic Varnish in the US is Golden, and they definitely recommend against using the stuff as anything but a final varnish.

See here. (https://www.justpaint.org/why-oil-painting-over-msa-or-archival-varnish-is-not-recommended/)

Granted, this article relates to tests of oil paint applied over a thin layer of varnish. They did not test an oil paint/varnish admixture. But the photos are still plenty scary.

I shall retreat to the traditional stance of keeping the worlds of acrylics and oil painting separate, with the exception of acrylic gesso, which has proven itself over the years.
For MSA acrylic varnish you can look Weber's Synvar (recommended as oil painting medium) and also Soluvar. For msa oil paint medium formulation try LUKAS Medium-3

Synvar:

A crystal clear, acrylic resin varnish, Synvar® is an excellent final finish for oil and acrylic paintings. It has exceptional adhesion with no tendency to crack or bloom and will dry to the touch in less than 30 minutes under normal conditions. The durable finish will resist normal acids, alkalis and moisture, and will not darken with age. When used as an oil color medium, it produces a soft chromatic quality. Thins with Turpenoid® or turpentine.


Do not use GOLDEN acrylic varnish as a painting medium because it contains amine UV stabilizer, that prevents oil paint to dry normally! NEVER use GOLDEN acrylic varnish for that purpose.

sarahsands
03-14-2019, 03:56 PM
Do not use GOLDEN acrylic varnish as a painting medium because it contains amine UV stabilizer, that prevents oil paint to dry normally! NEVER use GOLDEN acrylic varnish for that purpose.

That is precisely correct - it is not the underlying resin but the UVLS that inhibits oxidization. So definitely avoid because of those concerns. That said, solution acrylic resins have a long history as an additive in oil and alkyd paints and some were initially created for that purpose. We do make custom versions of the MSA without UVLS and have a Custom MSA Gel that is also UVLS-free, if folks in the US wanted to explore that. As part of some original testing, we have blends of MSA resin and oilpaint that are probably a good 25+ years-old in great shape. Flexible and with no cracks even in thick applications. The key is to keep the mixtures dominated by one or the other system - 25/75 in one direction or the other. Try to avoid 50/50 blends as one system or the other needs to dominate and encapsulate the other one. And while they now only have a niche market in conservation, we still produce a whole line of MSA Paints that are related and descended from the first acrylics for artists introduced in the late 40's called MAGNA. They do not contain UVLS and could be mixed with oils if desired.

You can find them on sites that sell conservation suppliers. For more information - and just in the spirit of sharing, not as a pitch:

https://www.goldenpaints.com/technicalinfo_msagel

https://www.goldenpaints.com/products/custom-products/mineral-spirit-acrylic-colors

Lastly, the products Gigalot mentions - Liquitex's Soluvar and Weber's Synvar- would be perfectly fine as well.

Richard P
03-14-2019, 04:56 PM
Does that suggest that oilpaint and MSA resin are more durable (in terms of cracking) than oil paints alone in the long term?

sarahsands
03-14-2019, 08:14 PM
Does that suggest that oilpaint and MSA resin are more durable (in terms of cracking) than oil paints alone in the long term?

It certainly does! And if you look up the tech sheets for many of these resins you will see that they are touted as compatible with medium- and long-oil alkyds and drying oils and will improve a film's durability and flexibility (since it acts as a form of plasticizer) as well as speed-up the drying time. But there are trade-offs of course (aren't there always?!). These resins need a higher aromatic solvent to be in solution - typically in the 10-20% range - and so you will find them very strong smelling, and would come with stronger health warnings. And technically solution resins remain resoluble - although if at a level of just a small addition it might be bound enough within the oil paint to not be an issue. I would need to do some testing.

For now I think it is a tool very few painters really explore anymore but certainly could be interesting for someone willing to take on some unknowns and able to handle the stronger solvent content.

Antonin
03-14-2019, 08:46 PM
Lastly, the products Gigalot mentions - Liquitex's Soluvar and Weber's Synvar- would be perfectly fine as well.
I believe Soluvar also contains a UVLS as their Safety Data sheet lists:

"Derivative of Benzotriazole; EC No. 400-830-7; Index No.
607-176-00-3"
https://the-bank.azurewebsites.net/download/31573

And:
"Soluvar Gloss Varnish is an archival yet removable varnish for acrylic and oil paintings that uses UV light stabilizers to protect your work. Glossy finish."
https://www.utrechtart.com/Liquitex-Soluvar-Gloss-Varnish--Liquid-MP-00669-001-i1002058.utrecht

Antonin
03-14-2019, 09:20 PM
These resins need a higher aromatic solvent to be in solution - typically in the 10-20% range - and so you will find them very strong smelling, and would come with stronger health warnings. And technically solution resins remain resoluble - although if at a level of just a small addition it might be bound enough within the oil paint to not be an issue. I would need to do some testing.

Your posts here are aways very helpful and thought provoking.
Turpentine, Spike Lavender, Rosemary oil or D limonene will each dissolve n butyl and iso butyl methacrylates completely.
It would be great if Williamsburg would start selling Elvacite 2044 100% dry solids.
The only retail source is Talas @ $53.65 per lb (compared to Talas' B 67 which is only $16.25 per lb).
If we had the solids we could dissolve only a small amount at a time in one of the vegetable solvents and not worry about long term shelf-life of the solution.
Although, years ago before Magna paints were discontinued, I bought a pint jar of Magna medium and it smelled like it had been dissolved in turpentine instead of petroleum solvents.

sarahsands
03-14-2019, 09:51 PM
I believe Soluvar also contains a UVLS as their Safety Data sheet lists:

"Derivative of Benzotriazole; EC No. 400-830-7; Index No.
607-176-00-3"
https://the-bank.azurewebsites.net/download/31573

And:
"Soluvar Gloss Varnish is an archival yet removable varnish for acrylic and oil paintings that uses UV light stabilizers to protect your work. Glossy finish."
https://www.utrechtart.com/Liquitex-Soluvar-Gloss-Varnish--Liquid-MP-00669-001-i1002058.utrecht

Yikes!! Good catch!! Thank you for pointing that out.

Gigalot
03-14-2019, 09:57 PM
Synthetic Resins - Acrylic [Methacrylate]


Various types of acrylic resins . . . . are manufactured under brand names such as Lucite or Elvacite (E. I. Du Pont, Inc.), Plexiglas, or Acryloid (Rohm and Haas Co.). Many of the acrylic resins are soluble only in strong solvents such as acetone or the aromatic hydrocarbons. However, a few, such as Du Pont's Elvacite 2044, which is n-butyl methacrylate, or Elvacite 2045, which is isobutyl methacrylate, can be dissolved in turpentine, V. M. and P. naphtha, or toluene. These resins are sold in the form of white granules or beads which may stick together in storage, especially in warm temperatures, to form soft chunks that look like dry artificial snow. They can be dissolved by the same method employed to make dammar varnish described on page 48. An acrylic resin already dissolved in mineral thinner is sold as Acryloid F-10 by Rohm and Haas Company.
Acrylic resins dissolved in petroleum thinners or turpentine are used in various brands of picture varnish ....for their clarity, flexibility, and agreeable gloss which is attractive to many painters.

Solutions of acrylic resins in petroleum solvents have been employed as fixatives and protective coatings for work done on paper in pastel and other drawing media...

Solutions of acrylic resin in turpentine and mineral spirits have also been used as binders for the artists' paints described [in documents related to synthetic resin paints and on page 198 in the book]. [p. 51]

[Kay, Reed. The Painter's Guide to Studio Methods and Materials. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1983.]

Gigalot
03-14-2019, 10:07 PM
Yikes!! Good catch!! Thank you for pointing that out.
But alfa-3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionyl-omega-3-(3-(2H-benzotriazol-2-
yl)-5-tert-butyl-4-hydroxyphenyl)propionyloxypoly(oxyethylen isn't HALS. It is common antioxidant and uv screen. It will oxidize soon, while HALS are cycling catalyst and has a long period of working time. Linseed oil also contains vitamin E but it will decompose on the surface soon after applying paint layer.

Antonin
03-14-2019, 10:25 PM
But benzotriazole isn't HALS. It is common antioxidant and uv screen. It will oxidize soon, while HALS are cycling catalyst and has a long period of working time. Linseed oil also contains vitamin E but it will decompose on the surface soon after applying paint layer.
If benzotriazole were so easily deactivated wouldn't it be ineffective as a sunscreen in (anti) suntan creams?
Are you saying that it wouldn't retard drying of oil paint, even a little?

Gigalot
03-14-2019, 10:33 PM
If benzotriazole were so easily deactivated wouldn't it be ineffective as a sunscreen in (anti) suntan creams?
Are you saying that it wouldn't retard drying of oil paint, even a little?
It will retard drying of oil paint however but not forever. :) At least it was used in urethane floor paint. (personally I had never tried soluvar, but my Nevskaya Palitra acrylic varnish dries just fine!)

Antonin
03-14-2019, 11:04 PM
At least it was used in urethane floor paint.
Isn't a sunblock always used with urethane to keep it from degrading in sunlight?

Gigalot
03-15-2019, 06:13 AM
Isn't a sunblock always used with urethane to keep it from degrading in sunlight?
It can also keep oil binder from degrading on daylight. We need more testing now. I think, that Sarah can help us with more testing. :)

sarahsands
03-15-2019, 08:54 AM
It can also keep oil binder from degrading on daylight. We need more testing now. I think, that Sarah can help us with more testing. :)

Duly noted and added to our list.....just realize it is a very veeeeery long list!!:)

My biggest concern is the unintended consequences. It always sounds good to absorb UV until it isn't and you realize it played a role somewhere else. And while benzotriazoles might not persist at the surface of films, they are considered to have long-lived, and at least theoretically indefinite, effectiveness within the film, where they convert the UV to heat. But also to a more limited degree can act as a radical scavenger, and that could mean an impact on crosslinking.

I say keep it simple rather than add in more complications and be open to the more important lesson from oil painting - patience.

Gigalot
03-15-2019, 03:10 PM
Good UV protector for oil binder are iron oxide pigments and copper (resinate) 2+ ions. Some of organic UV absorbents can boost drying speed at traced concentration and inhibit drying at elevated concentration.

AnnieA
03-15-2019, 04:05 PM
Hey, Sarah, thanks for all the detailed work - you really are an amazing source of information! These results are quite surprising.

I've seen some contradictory info, though. I wonder if you've ever seen the work of Tad Spurgeon, who seems to have gotten results that differ from Golden's. It may be because his process(es), require a lot of time with repeated washings of unrefined CP oil. Could it be that the washing process was different when Golden ran their yellowing tests? If you're not already familiar with Spurgeon, his page on refining oil is here: https://www.tadspurgeon.com/content.php?page=just+oil

I'd love to hear your thoughts, as I'm just beginning to experiment with Spurgeon's putty medium recipe, for which washed oil (which he says will yellow significantly less) is required.

sarahsands
03-15-2019, 05:24 PM
Hey, Sarah, thanks for all the detailed work - you really are an amazing source of information! These results are quite surprising.

I've seen some contradictory info, though. I wonder if you've ever seen the work of Tad Spurgeon, who seems to have gotten results that differ from Golden's. It may be because his process(es), require a lot of time with repeated washings of unrefined CP oil. Could it be that the washing process was different when Golden ran their yellowing tests? If you're not already familiar with Spurgeon, his page on refining oil is here: https://www.tadspurgeon.com/content.php?page=just+oil

I'd love to hear your thoughts, as I'm just beginning to experiment with Spurgeon's putty medium recipe, for which washed oil (which he says will yellow significantly less) is required.

Hi Annie -

We know Tad quite well and even had him up at the company several years ago where he led the entire tech team through a three-day workshop where we all did various versions of water washing raw linseed. And we continue to look into it and remain curious about its potential. If nothing else, it acts as a window into the past and a better understanding of the materials we use. Our library also has multiple copies of his book, Living Craft, which he just released as a final edition in paperback.

I know what you mean by the results seeming surprising or even contradictory. There were certainly some of those moments for us as well.

Lastly, I have corresponded with Tad about the results and, I think if there is something that unites us philosophically, is just being open to where the evidence leads, to being curious. So when you do get surprising results you go "huh - that's surprising!" and then try to figure out what the variables are that could be causing it. Or not causing it - as the case may be. So I wouldn't worry about it. It might be that under very ideal conditions - which has been the case here - that the differences between all the oils - poppy, linseed, washed, cold pressed - become negligible. But under a different set of conditions - say with higher humidity or higher temperature - that you would start to see another pattern emerge.

So I would keep doing what you're doing as long as it is engaging and interesting. The wonderful thing about exploring materials the way Tad and others have done is that it makes you intimate with the very stuff of our craft. And that is always a good thing.

AnnieA
03-15-2019, 05:28 PM
Hi Annie -

We know Tad quite well and even had him up at the company several years ago where he led the entire tech team through a three-day workshop where we all did various versions of water washing raw linseed. And we continue to look into it and remain curious about its potential. If nothing else, it acts as a window into the past and a better understanding of the materials we use. Our library also has multiple copies of his book, Living Craft, which he just released as a final edition in paperback.

I know what you mean by the results seeming surprising or even contradictory. There were certainly some of those moments for us as well.

Lastly, I have corresponded with Tad about the results and, I think if there is something that unites us philosophically, is just being open to where the evidence leads, to being curious. So when you do get surprising results you go "huh - that's surprising!" and then try to figure out what the variables are that could be causing it. Or not causing it - as the case may be. So I wouldn't worry about it. It might be that under very ideal conditions - which has been the case here - that the differences between all the oils - poppy, linseed, washed, cold pressed - become negligible. But under a different set of conditions - say with higher humidity or higher temperature - that you would start to see another pattern emerge.

So I would keep doing what you're doing as long as it is engaging and interesting. The wonderful thing about exploring materials the way Tad and others have done is that it makes you intimate with the very stuff of our craft. And that is always a good thing.
Yes, I'll keep doing what I'm doing, because the big plus for me is the way the putty medium makes the paint easier to work with. I guess I'll just have to stay puzzled about the counter-intuitive results (especially why a hand refined oil that's less yellow in color doesn't apparently result in less yellowing overall) until someone works out the puzzle.

Many thanks, Sarah! Your input is always appreciated!

sarahsands
03-15-2019, 05:57 PM
I guess I'll just have to stay puzzled about the counter-intuitive results (especially why a hand refined oil that's less yellow in color doesn't apparently result in less yellowing overall) until someone works out the puzzle.

If it helps any, I had my hopes pinned on my own small bottle of linseed oil that I kept in one studio window after another for 20 years. I would have put money down it was going to outperform anything after two decades of being sun-bleached into a pale almost colorless oil...but alas, it's in the middle. :confused:

Gigalot
03-16-2019, 04:16 AM
If it helps any, I had my hopes pinned on my own small bottle of linseed oil that I kept in one studio window after another for 20 years. I would have put money down it was going to outperform anything after two decades of being sun-bleached into a pale almost colorless oil...but alas, it's in the middle. :confused:
Add 20% Synvar to your "magic" linseed oil and it reduce yellowing significantly!
I can't understand Tad Spurgeon when he try to use something "organic" in acrylic era! :confused: :eek: :angel: That reminds me "flat earth" idealists. "Organic" must be soy or potatoes, while technical grade product must be trusty scientifically refined.