Introduction
For some time, our recommendation for artists using oils over acrylic has been to work over harder, matte acrylic surfaces and avoid working on softer gels and gloss products. Our intention was to optimize the level of adhesion that would be achieved on a toothier surface as well as avoid the potential for future cracking as the oil paints become more brittle. While we have not seen adhesion problems of oils on any type of acrylic, recent testing has shown the potential for cracking in certain instances and conditions when applying artist oils over all of the many brands of glossy acrylics we have tested. Though we have not received notice from artists of this phenomenon, we are able to repeat this specific type of cracking in our Lab.
What follows is an overview of our testing, results and updated recommendations for applying oil colors over acrylics.
Middle: Titanium White PW6 – over gloss acrylic gel on gator board
Right: Mars Yellow Light PY42 – over gloss acrylic gel on gator board
Methods & Materials Tested
Applications included multiple substrates: stretched canvas, unstretched canvas, canvas board, wood panel, polyester sheeting and lacquered paint testing cards. The type of substrate has minimal to no impact on the outcome. Lacquered paint testing cards were the preferred substrate to create repeatable and measurable results.
Multiple acrylic grounds, gels and mediums from different brands were evaluated, including acrylic gessoes, molding pastes, matte mediums, acrylic gels and mediums with different sheens, as well as acrylic colors.
Multiple artist oil brands and colors were evaluated. Several colors were selected for increased study because they exhibited the strongest effects of cracking.
Acrylic mediums and grounds were applied onto lacquered cards using a draw down blade to assure uniform thickness as well as to understand how various thicknesses of these mediums might exacerbate the resulting effects. Several substrates with older acrylic applications were also evaluated. Materials were allowed to dry for at least three days in ambient conditions before oil applications. The age of the acrylic had insignificant impact on results.
Oil paints were knifed onto the test surfaces and thicknesses were measured using a micrometer. Tests were performed with and without the addition of alkali refined linseed oil, alkyd medium and stand oil.
Right: Oil paints knifed across acrylic application with variable thickness.
Results: When is Cracking Happening?
Our testing indicates that if cracking develops in the oil layer because of this phenomenon, it is during the early stages of drying – as the paint transitions from being wet to touch dry. Fast-drying colors like Mars Yellow or colors that are susceptible to this type of cracking like Ultramarine Blue, may develop hairline cracks within a day or two. Slower drying colors can take weeks or even a month to show any issues, if ever. It appears this cracking does not develop further once the color is fully touch dry.
Summary of Findings
- We have not found cracking in oil applications over GOLDEN Acrylic Gesso, Sandable Hard Gesso, Molding Paste, or surfaces sized with Rabbit Skin Glue when these products are used on their own with oil paints or grounds applied directly. This is also true for most other brands of acrylic gesso we have tested.
- We have not experienced adhesion or embrittlement issues related to painting oils over acrylics (other than zinc rich oil paints).
- Cracking is mostly happening in oil paint or oil ground with no oil or solvent added, applied directly out of the tube or container over the acrylic surfaces. These oil applications are roughly between .05mm and .25mm, which is the thickness of 1-5 sheets of office paper. Layers that are thinner or thicker do not seem to crack.
- Glossy acrylic mediums and gels are associated with the most cracking in lean oil layers applied on top.
- Satin, semi-gloss and matte acrylic mediums, acrylic colors, and aggregate pastes and gels can be associated with minimal or microscopic cracking in oil layers.
Recommendations
Here are some recommendations for artists using oils over acrylics with suggestions for mitigating the potential for cracking. Because our research is evolving, these recommendations may change. An editor’s note will appear on the top of this article if we change these recommendations in the future.
- Use three or more coats of professional, white acrylic gesso as a ground for oil painting.
- Avoid glossy acrylic products in any preparatory layer of an oil painting. This includes products that we have recommended for sizing or preparing surfaces in the past, such as GAC 100, GAC 200 or GOLDEN Gloss Medium.
- Add oil painting medium or binder to oil paints if working over satin, matte, aggregate products or acrylic colors. We have found adding 5% or more of medium to the paints significantly reduces the potential for cracking.
Acrylic Isolation Layer Before Oil Paints
Gesso helps block cracking associated with underlying gloss acrylics with 3-4 coats, however, some artists want to be able to see through to the underpainting or the substrate. We have previously recommended that a layer or two of Fluid Matte Medium or Matte Medium be applied over glossy acrylic sizing or acrylic colors to provide additional tooth before subsequent application of oil paints, but in some cases, their addition makes the cracking even worse. For this reason, we no longer recommend Matte Medium or Fluid Matte Medium as an additional isolation layer over other acrylic products in preparation for oil painting. Instead, modify oil paints with 5% or more medium or oil binder if painting directly over acrylic colors or any matte acrylic being used as a translucent ground.
Acrylic Color Underpainting
We have not completed a comprehensive review of all of our acrylic colors and formulations, but so far have seen minimal cracking over acrylic colors from multiple brands, as compared to acrylic mediums. Generally, if acrylic colors are being used for underpainting oils, we are currently recommending modifying oil colors as described below.
Modify Oil Paint Applications with Oil or Medium
The acrylic products listed in the chart above are not associated with cracking and can be used without concern. However, when other acrylics are used in the under layers, including acrylic colors, we recommend modifying your oil colors before painting.
Adding 5% or more of stand oil or alkyd medium, or 10% linseed oil to the oil paints can reduce or eliminate cracking entirely. While adding just a little solvent to color or oil ground did not change outcomes, we found that very thin solvent-based washes of color did not seem to crack in most applications.
Center: Mars Red with alkyd medium – Minimal cracking at 4% no cracking at 6% and10%.
Right: Mars Red with stand oil – Minimal cracking at 2% and no cracking at 4%, 6% and10%.
In Closing
This research exposes limitations to how oils and acrylics can be used together. While this information might raise concerns, it is good to know that cracking is avoidable with certain working methods.
We are also trying to understand why this phenomenon seems to be unreported or under-reported in the normal course of painting oils over acrylics, a method that has been used successfully for decades by artists.
We are committed to continuing our own research and are in communication with multiple conservation research partners to better understand this issue so we can provide artists and other art material manufacturers with improved recommendations.
Please join us May 10 at 2pm EDT for a Facebook Live event where we will answer your questions and demonstrate our new recommendations for painting oils over acrylics.
If you have any questions or concerns, please do not hesitate to leave a comment or contact us at help@goldenpaints.com or call 800-959-6543.
Very interesting, but also surprising!
The fact that adding oil to the paints stopped the cracking could suggest that the paints were under-bound, but I would expect the surfaces using gloss acrylic to be less absorbent than matte or Gesso. What about toothy clear gesso which has a rough surface, was that tested?
Also interesting that it seemed to only occur in one range of thicknesses. I would expect it to occur in thicker paint films as well, but that’s not what you found.
Did you try ACM panels as well BTW?
I’m not sure what else would cause paint films to crack like this on a rigid surface when the layer underneath was not oil that was already drying..
Hello Richard,
Thanks for your thoughtful comments. We are certainly intrigued by the underlying mechanism that is causing this cracking!
You are right to question the absorbency of the different products. That is something we have looked into – cracking happens more on glossy acrylics, which are less absorbent, and less on matte or other absorbent products – which seems counter intuitive. We have looked at clear gessos, Matte Medium, Pastel Ground and found variable results – better than gloss, but still not perfect. In general, matte products seem to crack less which is why we are recommending adding oil when working over these type of products. Even that 5-10% seems to be enough to push applications into the safe zone.
We have not seen cracking with this phenomenon in thicker applications. That is not to say that thicker applications might not have their own issues in the future. But, with this it seems to be isolated to that specific range between .05mm -.25mm. This range seemed to be the zone regardless of the substrate. We didn’t try ACM, but did work on wood panels and canvas mounted to panel. The laminated cards provide a nonabsorbent, inert surface and seemed to provide consistent results with all the other substrates we tested.
BTW Scott shared your recent portrait and it is very lovely!
Take care,
Greg
Hi Greg,
Thanks for the kind words on my portrait 🙂
I know that acrylic paint films swell and then shrink back when exposed to water. I am wondering if perhaps they are swelling with the oil and the fast expansion and contracting is causing cracking? Adding oil would slow down the drying process and perhaps the resulting stresses from the acrylic expansion?
Just an idea..
Hi Richard
It is an excellent idea. We will be investigating questions like this with our research partners at conservation departments in the US and Europe who have the kind of tools necessary to measure swelling and/or to be able to detect migration of specific compounds from one layer to another.
Thanks for your thoughts!
Greg
Thanks Greg 🙂
Another quick thought.. Although not sound archival practice, perhaps testing oil paint over acrylic gloss medium that has first had a couple of layers of gloss varnish applied over the acrylic medium? It would be interesting to see if this has any effect or not.
So many things to test!! The question then becomes, why is the GAC or gloss medium so important that an additional type of material should be introduced into the structure of the painting.? Varnish is a tricky material to include, as it is resoluble and most natural varnishes tend to yellow and harden with age. Modern varnishes can introduce a whole other group of problems in that some acrylic resins are lipophilic and can soften when wet oils are applied over top. So, those certainly would not work! We will keep looking for appropriate products that may be used for this purpose.
Take care Richard,
Greg
Very interesting! I like that time-lapse of the paint drying. Did you try brushing the paint on instead of using a palette knife? Could the striations from a brush lessen the developing paintfilm tensions? I noticed that some of the ridges left from the palette knife developed into cracks on your video (while some cracks just developed where the paint was flat).
Hello CF
Thanks for your feedback. Great question!
Yes, we did test brushing as well as smooth applications. The striations in the brush strokes seem to provide a “weak point” in the application where cracking might be more likely to develop as long as it is within the thickness range mentioned in the article. We have seen some cracking develop along the base of a brush strokes – following the striations of the stroke (This was mostly only observable under the microscope at 10 or 20 times magnification). We saw this with knife applied applications as well, where cracking would follow the base of a ridge or texture in the application.
Take care,
Greg
Will putting clear acrylic gesso over the acrylic underpainting help to avoid cracking?
Hello Sooz,
Not necessarily. We have seen some cases of lean oil paints crack over Clear Gesso or Matte Mediums that have been applied over acrylic colors. If painting oils over acrylic colors is a necessary part of your practice, we are recommending adding at least 5% oil or medium to the oil paints and then working directly over the acrylic colors. Clear gesso may not help improve outcomes.
Thank you for this information. Very helpful. It’s not a necessary practice, just felt like a quicker (drying time) step. With this knowledge, I think I’ll finish all future acrylic paintings with acrylic paints and mediums and begin any new oil paintings using oil paint only. This is timely, as I was just getting ready to start a large oil painting over an existing acrylic underpainting, and now will change the plan and finish it in acrylics. Thanks so much.
Hello Again Sooz,
You are welcome! That sounds good. Keep in mind, that if you tend to add medium to your oil colors anyway, then you should be fine to work with the modified oils over the acrylic underpainting. It is understandable that you might be reluctant, but please know that any cracking over acrylic color even with lean oil paint, is minimal when it occurs, and in those cases often only visible with magnification. So, oil additions should push things into the safe zone.
Thanks for your feedback an comments!
Greg
Though I don’t directly paint over acrylic other than acrylic gessoes, I did note cracking over a slightly slick alkyd primer some decades back. (Which I quickly discarded BTW.) The drying cracks seemed much larger, if fewer in number, when used and painted over on non-canvas panels. On canvas the cracks were much smaller and followed the brush strokes and weave of the fabric. The cracks on the canvas were only noted under careful inspection and seemed to some degree to read as a feature of the creative process. As such they didn’t seem very objectionable. However on the smooth panels the cracking effect was judged more visually disruptive. I think the cracks were fewer but larger on the slick panels because the paint had nowhere to hold or be impeded in its shrinkage. The paint film was largely allowed to freely retreated in dimension until it broke into visible cracks. Where as every bump in a canvas weave provided a natural, but smaller break point.
Marc Kingsland
Hello Marc,
Thank you for your feedback. This is very interesting, though it sounds like a different mechanism at work with your cracking. Did your cracks develop upon drying of the oil colors over the ground, or did it take time? One difference is that in our testing, the adhesion of the oil paint or oil ground to the acrylic, even glossy acrylic, is excellent. There was no slipping on the surface or failure in that regard. Could the cracked paint on your surface be chipped right off or were the platelets fully adhered?
Best,
Greg
The cracks appeared within days or weeks. Too much time has passed to be precise as to how quickly the cracks manifested, but basically upon drying. The paint seemed to be fully adhered, but I didn’t attempt to chip it off. However I had little faith in the panel pictures so never offered them for sale. Plus they also seemed in part to be visually pre-damaged.
Marc.
Thanks for the follow up Marc. That is very interesting!
Can I still size a panel or canvas using Gac-100 to prepare for an oil painting, I use an oil ground on top of Gac-100 after 4 days to prepare the surface for oils.
Hello Martin,
We have changed our recommendation based on the findings reported in the article. We have seen lean oil paints (directly out of the tube, without the addition of oil or medium) crack over GAC 100 and other glossy acrylic products. For that reason we now recommend preparing canvas or panel with at least 3 coats of acrylic gesso only (without GAC 100), allow that to dry for at least 3 days, then apply the oil ground over that. Oil paints can also be applied directly to the Acrylic Gesso if desired. We have not seen this form of cracking develop over the professional acrylic gessos we have tested.
Please let us know if you need additional clarification. You can email directly at help@goldenpaints.com
Best,
Greg
Along these lines, what about the use of a GAC to stiffen the canvas under an acrylic gesso?
Marc Kingsland.
Hi Again Marc,
We tested GAC 400 earlier to see if it improved results under the GAC 100, which it didn’t, but neglected to look at its influence under Gesso. We have the canvas ready to test and should have results end of next week. We will update this communication then AND will review those results on our May 10th Facebook Live event at 2pm.
Thanks for helping us cover all the bases!
Greg
First I would like to thank you all for your continued research. In this case, I am confused though–the “phenomenon” does not seem to be clearly defined anywhere other than an insinuation that it is the cracking itself. However, this line seems to indicate that the phenomenon is something other than the cracking, “Our testing indicates that if cracking develops in the oil layer because of this phenomenon…” Can you please give a clear description of what the actual phenomenon is (if it is something other than the cracking itself?) Thank you.
You are welcome, and thanks for your feedback Anthony!
We may have inadvertently confused the cracking itself with the mechanism that is causing the cracking, and called them both a “phenomenon” at different points in the article. In relation to the quote you provided, we were referring to the mechanism that is causing the cracking. We understand the timing of the cracking, what combination of materials can cause the cracking, what combination seem to resist cracking and some of the parameters around the cracking…but we do not understand why it is happening. We have presented this information, in detail, to a dozen world-class conservation scientists and not one has ever reported on or researched this topic. It is because of this unknown quality that we refer to the mechanism behind that cracking as a phenomenon.
We look forward to continuing our research and uncovering more about these strange and nuanced materials…and then of course sharing the results with you!
Thanks again and take care,
Greg
Understood Greg! Thank you for your quick and thorough response and for all you do. Best wishes!
Greg, thank you so much for providing us with the findings of your research. It’s going to take awhile for me to wrap my head around this, because my absolute favorite “primer” to paint on in any medium (gouache, acrylic, or oil) is a couple of coats of Golden Matte Medium! I love that I can see the color of the substrate. I love the way it grabs the paint, that I can wipe right back to the surface, and that it is less absorbent than gesso. I use it in my sketchbooks, on canvas panels, on boards, on rag matboard… I like it so much better than gesso, and hate to say goodbye! I am also a little confused about the distinction between gloss products and matte. It says in the article that gloss acrylic products produced the most cracking, but then it said that a coat of matte medium over the gloss was sometimes worse. Is that due to the extra layer of acrylic, or due to the matte medium? So is it better to use matte medium than gloss medium if choosing one? If I add a bit more alkyd medium to my oil paint, would that resolve the issue for me in any case, and could I then continue using the matte medium as I have been? Many thanks for any clarification you can provide, and also for the upcoming FB Live talk and Q&A.
Hello Jamie,
Thank you for your comment/ question. It sounds like you are understanding correctly – Gloss acrylic mediums are causing the worst cracking. Matte Medium and Fluid Matte Medium are less, but there is still the potential for cracking in lean oil layers that are applied over these products. Because the potential is reduced over Matte Medium, we are not recommending against it entirely, but rather simply adding oil or medium to your oil colors to reduce or eliminate the risk. We have found additions of about 5% or more is enough to bring oil applications into the safe zone, especially when working over Matte Medium or acrylic colors. 5% is not much at all, a couple drops of oil to a small nugget of paint.
We will be sure to reiterate this idea during the FB live, but in the meantime please follow up with any additional questions.
Best,
Greg
Perfect! Thank you so much, Greg!
You are welcome!
I’m confused. Does this apply when using Gloss Glazing Liquid too or just GAC 100 and gloss mediums/gels? (i.e. If I am using a pre-primed acrylic gessoed canvas with no additional gesso added, and then using Glazing liquid mixed with HB paints on any layer before the subsequent oil layer(s) are added, will the cracking happen or no?)
If GAC 100 presents an issue, what do we use to seal the wood before applying gesso? I hope my questions made sense. Lol
Hi Stephanie,
Unfortunately, we cannot say for sure. It is very possible that you will never see cracking even with oils over Glazing Liquid, as your technique may be outside of the very specific parameters that can lead to this cracking issue. In general, we found that glossy mediums, including Glazing Liquid Gloss, when used either on their own or combined with color under oils contributed more to this issue than matte mediums/gels and gessoes or grounds. We found that when painting oils over glossy acrylic products, adding 10% medium or binder, such as an alkyd medium or linseed oil or about 5% stand oil mitigated the issue in the vast majority of our testing.
As for blocking SID with GAC 100 or Gloss Medium, this is mostly an issue when painting with slow drying acrylic or thick acrylic applications over wood panels, especially MDF or similar pressed wood. Those have the most colorants that can impact you acrylic layers. Oils are not impacted by SID, as they do not activate the water soluble colorants in the wood. We simply recommend using about 3 coats of Acrylic Gesso to prepare wooden panels for oil painting.
We hope this helps!
Greg
I understand Greg–Thank you. I’ll stay tuned for future updates. Thank you for all you do. Best wishes-
Appreciate it Anthony!
Have you looked at oil & cold wax over acrylic? If so, what was the outcome?
Hi Janet,
Thanks for your question!
We have not. But, We have had several artists request information on that combination already, so will be testing ASAP. We will share results during our FB live event on our Golden channel on May 10th and will come back in to these comments and update our replies with what we find.
Take care,
Greg
Thanks, this is concerning. I’ve been following Golden’s recommendations closely and swore by GAC100.
“We have not found cracking in oil applications over GOLDEN Acrylic Gesso, …. This is also true for most other brands of acrylic gesso we have tested.”
What about pre-primed canvas and linen (usually acrylic, and oil ones can contain zinc)? I wonder if canvas companies do their own tests like Golden. Should I buy single layer “pre-primed” linen or canvas and apply my own extra Golden gesso layers? I couldn’t be bothered to rinse then dry and gesso raw linen.
It is nice to paint on clear primed linen. I wonder if extra tooth in rougher linen helps, although that’d probably help adhesion nor cracking, (and what about testing primed textured linen versus poly which is smooth).
Is there an additive in all acrylic paints that could cause the problem?
I also wondered if you’ll test paint brush strokes versus draw downs
Where will I be able to find the link to watch the video afterwards? Thank you for this
Hello Lej,
Thank you for your comments. Did you ever see any issue when working oils over your GAC 100? Did you use Oil Ground or Gesso over the GAC?
Most pre-primed linen or canvas use a universal primer which is typically acrylic. An additional coat or two of Golden gesso or another professional brand should be good to make a nice surface for oil painting and should block oil with a total of 3 coats. Be sure to let the gesso dry for about 3 days before painting over top with oils.
We have seen some cracking over clear gessos, so please note the recommendation for adding oil to the paints before painting over those surfaces. 10% of a regular drying oil and 5% stand oil or alkyd medium should be good to get you into the safe zone.
We have not been able to isolate a specific ingredient that seems to cause this issue. our investigation will continue with conservation scientists in the US and Europe to try and learn more about this phenomenon. We will certainly share our results.
The Facebook video should remain on the site after the event so you can go back and watch it later. It should also be on our Youtube channel.
Take care,
Greg
Thanks for your research. I still have some panels prepared years ago, using GAC 100 for sizing, over which I applied many, many coats of acrylic gesso admixed with marble dust and talc. (I like an absorbent surface.) After reading this, I’m a bit concerned, but I think I would still take the chance of using such a panel for oils.
1. I’ve not had any problems so far with such panels.
2. The years of aging have probably helped.
3. I tend to apply oil paint thinly.
4. Your testing doesn’t really replicate the preparation I did.
But I’ll let you know if the oil paint ever cracks or flakes or hops away from the surface.
HI Joseph,
Thank you for your comment. Glad to hear you have not seen any issues so far! We expect many artists are also using oils over acrylic without issue, but just want everyone to know there is this potential when combining these two materials.
We tested 3-4 coats of gesso over GAC 100 and found the gesso layers seemed to block most of the tendency for cracking in overlaying oil layers. And when it did crack in this situation, it was miniscule or microscopic cracking. If a small amount of oil or medium was added to your oil colors, then it is very likely that cracking would not occur with this preparation. The addition of talc and marble dust to the gesso probably help too.
In reference to #2, we did not find aging of the acrylic help noticeably. And #3, thin, lean applications is actually where we are seeing the issue. So that is something to look for. Let us know if you come across anything in your older works or if new projects develop cracking upon drying of the oil layers.
Best,
Greg
I’m in a similar situation to Joseph; I’ve used GAC 100, GAC 200, and combinations of the two as a sizing layer under acrylic gesso (specifically, Sandable Hard Gesso) for many years, and have never experienced any cracking. I checked a couple of older paintings under magnification (just using a jeweler’s loupe–I don’t have a microscope) and can’t see any evidence of cracking on those.
My typical preparation is two coats of GAC, applied with a brush and allowed to dry overnight, followed by 6-8 coats of Sandable Hard Gesso (which sounds like a lot, but I like to sand it smooth, and want to have a thick enough application that I don’t sand through). Usually over hardboard, sometimes over wood. My initial oil paint layers are always thin and lean; my initial layer is usually a mix of lead white and raw umber rubbed on very thinly with a (gloved) hand, to tone the ground. Initial paint layers following that are usually a very thin ebauche of straight paint, or paint thinned very slightly with solvent.
I’d love to see more testing on this specific scenario (GAC or acrylic medium under gesso of varying types and thicknesses), as I suspect that this is how most oil painters use those products (there are also a number of companies, like Trekell, selling acrylic-primed supports that have been sized with GAC 100). I’m hesitant to remove the sizing layer from my process altogether, because I worry about SID affecting the ground. Perhaps it would be safer to switch to matte medium under gesso? Or perhaps to another type of sizing layer altogether, like Paraloid B72?
Hello Benjamin,
Thanks for your comment. Great to hear how folks are preparing their supports and starting paintings! Because this issue is so specific with the combination of materials and thickness of application etc, we feel that if you are not seeing and cracking with your current technique, there may not be any reason to change. Even with the sanding, that is many layers of SHG. We tested up to 4 layers of regular white Gesso and found consistently, that the effects of GAC 100 were blocked by 3-4 layers. It is understandable that you do not want to remove your sizing layers from your process, but with so many layers of Sandable Hard Gesso combined with the initial layers of Flake White and Umber, any SID that might come through to the Gesso layer will likely be covered by those colored layers. Switching to Matte Medium will not help block SID, as we have not found that product to be effective in that way. Also, we do not recommend Paraloid acrylics directly under oils because we have seen the solventborne acrylics interrupt drying of some oil colors, causing them to remain sticky for an extended period. That said, we have not tested paraloid B72 as a sizing under many layers of Sandable Hard Gesso and do not know if it blocks SID.
Best Regards,
Greg
Hello Greg,
I apply very thin layers of Burnt umber directly from the tube on top og GAC100 and haven’t seen any cracking yet. I often ‘oil out’, that is applying a thin oil-layer on top of the dried oil, before applying another layer.
Might the ‘oiling out’ substitute the adding of oil into the color in application?
(And thank you very much for this news-letter, this is my first edition and it is already super relevant)
Best Regards
Claus
Hello Claus,
We are glad you found the article helpful! Thank you for the feed back! It may be that the burnt umber is not as vulnerable to this type of cracking as some other colors. If that is the case, then great. We have tried to ascertain which oil colors are most likely to crack in this situation and why, but have not found the pattern yet. If the burnt umber is drying and not developing cracks as it becomes dry to the touch, then it is likely not to have an issue. The oiling out is fine as a preparation for the next layer, but it shouldn’t have anything to do with preventing this type of cracking. That said, it may support the layer that the oil gets worked into, so the second layer may benefit from the oiling out.
Curious if there is an alternative to the GAC 100 for you moving forward. What do you like about that product, and can it be replaced by several layers of Gesso?
Best Regards,
Greg
Hello Greg, sorry for this late reply, these forums are new to me.
I use the GAC 100 for two reason:
1) This method was introduced to me by the artist Annie Stegg Gerard in a tutorial I bought. She first does a pencil drawing, fixates that with GAC100 and then uses the raw umber as an underpainting (sorry that I wrote: burnt umber previously). Then she goes on to do elaborate oil paintings on top of that. I haven’t written to her about your findings, but she doesn’t report any cracking.
2) I do an elaborate pencil-drawing on the paper first, and I want to preserve some of that linework in the finished piece. Because of its low viscosity, GAC100 can be applied without smudging the pencil. The smudging could probably be prevented with a layer of spray coating before applying a more viscous protection.
The glossy surface of the GAC100 also lets me mix pencil into the raw umber, the oil dissolves the pencil line achieving a ‘lost and found’ quality.
I have uploaded two photos of recent experiments here:
https://www.dropbox.com/sh/h7dyims0he0qcvv/AABk1xC9LInCYu_HdljfmVSDa?dl=0
I could use Winsor and Newtons Clear Gesso Base instead of GAC100. Would you recommend that?
Thanks again
Hello Claus,
Thank you for the details of your process. Those are great little paintings!
If you have not seen any issues to this point, it may be fine to just continue as you are. In general though, we have seen better results over Matte Medium or Clear Gesso than working oils over GAC 100. Are you using the GAC 100 to both size the paper and lock down the pencil? Or do you have Gesso on the paper first, then pencil, then GAC 100?
If the paper is already Gessoed, then you might try drawing with pencil and then working the oils directly over top without isolating, Or substituting the Matte Medium or Clear Gesso in place of the GAC 100 if it is just locking down the pencil. Your oil layers seem relatively thin, which may be below the threshold for when we are seeing this issue. Also, we have not tested a variety of umbers from different manufacturers, but our umbers do not seem to show a propensity for cracking due to this phenomenon. We will have to report on that later as we get more results.
Hope this helps.
Take care,
Greg
Hi Greg, thank you for the awesome content that you produce! I apologise if I am about to repeat a question that has already been asked. I have read the comments, but am still puzzled by the GAC100 issue. I paint on wooden panels, which I first seal with GAC100, before applying gesso. My oils are applied directly over the gesso. Am I correct in concluding that I should rather apply the gesso directly to the panel? Also, if I may add a second component to this question – I have read that sandable gesso should always be applied over a layer of regular gesso. Is this true? In other words, is it your recommendation that a panel be primed with a layer of regular gesso, followed by sandable gesso, followed by oil paint, thus leaving out the GAC100? Your advice would be appreciated!
Hi Alex,
Thanks for your question. Yes, we are recommending against GAC 100 or Gloss Medium as a preparatory layer before oil painting. Instead, Gesso can be applied directly to the panel in as many coats as desired, allowed to dry for at least 3 days, and then oils over top of that. The Sandable Hard Gesso can be applied directly to the panel too, but the concern is if the panel is too absorbent, then the Sandable product may crack upon drying. Absorbency of the surface may depend on the type of panel that is being used. Most can take the Sandable Hard Gesso directly when it is applied in thin layers. You should be able to see if there is an issue right away as the SHG dries.
Hope this helps. Let us know if you have additional questions.
Greg
Hello,Greg
Thanks for your newest testing , it is very helpful ,and i wonder if you have done any testing for Very Large size oil painting ,Like 2meters * 3meters for Oils Over Acrylics ?
1# What is your recommendation for large Size oil painting ? Linen Fabric +3 layers Golden Acrylic Gesso (3550 ?) +Alkyd Titanium Oil Ground ?
2# Alkyd more adhesive than Linseed oil ?
3# PVA 2 Layers +Alkyd Titanium Oil Ground ,Acrylic Gesso 3layers+ Alkyd Titanium Oil Ground , For Large size Oil painting Adhesion ,Which is better ? PVA or Acrylic Gesso ?
Thanks !
Hello Gavin,
Thanks for your comment. We did not test extra large canvases, but imagine this issue could effect surfaces of any size with the right combination of materials. For a successful outcome, either PVA Size or Acrylic Gesso could serve to prepare the canvas for oil ground. The PVA does not create much build on the surface, so if you want maximum canvas texture, then go with the PVA. If you want to fill the weave some and increase stiffness of the canvas (which may be good on a larger piece) then 3 or more coats of Gesso should be sufficient to block oil and prepare for the oil ground. Adhesion should be equally good for both. Alkyd binder or oil binder both provide good adhesion to a properly prepared surface. Applying Gesso with a trowel can speed the process and create a smoother surface.
Hope this helps. Best wishes with your work!
Greg
Hello Lori,
That is a good question. We have not tested oil paints and mediums on vinyl wallpapers. Adhering the paper to a panel should provide support for the oils as they age, which do become increasingly brittle, but there may be different types of degradation associated with the wallpapers that we do not know about. Acids in the paper can cause yellowing or embrittlement in the paper fibers over time regardless of whether the paper is embedded onto a surface. Also, some vinyls contain plasticizers that can evacuate over time. As these volatile compounds leave the vinyl, they can trapped in the oil layers over top and may disrupt the drying of that film. They may cause the dried oils to become sticky or soft over time. We have seen this with acrylics over vinyl and are only speculating that this might happen with oils, but its a potential. Before going too deep into a body of work with this combination of materials, it may be good to test on a small scale. Also, regarding the topic discussed in the article, if a gel or medium is used to adhere the vinyl to the panel, and the oil paints come in contact with that acrylic product, then that may cause other issues, such as the type of cracking that we have recently discovered. To discuss this issue further please feel free to call 800-959-6543 and ask for Greg in technical support. Or email gwatson@goldenpaints.com.
Best Regards,
Greg
Hi Greg
Having read the article and discussion below, I can say I use similar (although not exactly the same) process as Joseph Cannon described above. Right now, I’m about to finish preparation of three panels. In my case it is:
1. I mount fine textured linen over braced HDF board using acrylic glue.
2. After a day or two I rub the surface of the linen with pumice stone to get rid of little knots; even though it is extra fine textured linen, I find these little knots annoying.
3. A layer of Fluid medium matte. After it has dried, some rubbing with pumice stone again. Then another layer of Fluid medium matte.
4. Two layers of acrylic primer applied with palette knife to fill the weave of linen (which is still slightly present).
5. Another 3 – 4 layers of acrylic primer applied with brush.
Sometimes I paint directly with oil paints over this, sometimes I apply oil ground – in this case e.g. Williamsburg Titnaium or Lead ground thinned with turpentine in proportion 5 parts ground to 1,5 parts turpentine. Whether first or second case, I typically wait 3 – 4 weeks before applying oil ground or painting with oils over acrylic primer. As for acrylic primers, I use either Golden Gesso or Lascaux Gesso (first 3 layers) and Lascaux Primer (second 3 layers).
And for the very first layer or imprimatura I usually use either paint straight from tube or paint mixed with medium made from chalk ground in linseed oil (similar to Velasquez medium by Natural pigments) and in both cases sometimes thinned with small amount of turpentine or spike oil.
One panel was prepared with 3 layers of WB Titanium oil ground and beneath it, If I remember well, were 4 or 5 layers of Golden Gesso, and beneath the Gesso Fluid medium matte and GAC 100. The oil ground was left to cure for few months. I haven’t observed any cracks in cured oil ground, or succesive paint layers (so far 2 layers applied).
So, in short; linen mounted on HDF, then sized with Fluid medium matte, then prepared with 5 – 6 layers of acrylic primer and then painting with oils. I guess, I could say the same as above mentioned contributor Joseph Cannon, i.e. „Your testing doesn’t really replicate the preparation I did.“ Well, anyway, I guess I should be fine, what do you think?
Best regards
Ivan
Hello Ivan,
Thanks for describing your preparation in such detail! It sounds like you are applying enough Gesso layers to block any effects that might come from the GAC 100 or Fluid Matte Medium. And if you are adding some medium to your initial layer/imprimatura, then that would provide even more protection from experiencing this issue. In the future if you can remove the GAC or FMM from your preparation, then there should be no concern for potential cracking in the oil layer especially when you are using lean oil paint. Let us know how it all goes and keep in touch!
Take care,
Greg
Hello Greg
Thank you for feedback.
As for your recommendation about removing GAC or FMM as a possible practice in the future; I’ve never tried applying acrylic primer directly over raw linen, but I think it could be somewhat… more problematic for me. You see, raw linen is of course absorbent surface. GAC 100 and FMM can size the surface, thus making it almost non-absorbent. Since these are basically only fluids and Gesso contains certain level of solids, I guess it could be difficult to brush the Gesso out evenly as it would dry too fast. The thinning with water might be necessary. Also, I wonder if dried Gesso could be rubbed with pumice stone (to remove little knots) in the same way as dried FMM. I don’t know. Maybe I’ll try it.
Also I’ve been thinking about the recommendation in the article to wait at least 3 days after applying acrylic dispersion or Gesso before painting with oils over it. Of course „at least 3 days“ means 3 and more, but I wonder if it shouldn’t be at least 4-5 days for one layer of Gesso. That is, in case of 4 layers at least 3 weeks. Maybe 3 days are just not enough for all residual moisture in acrylic primer to evaporate and this could be part of problem?
One recommendation in the article is to size with PVA size. I’ve never tried it, what I can readily buy here (that „here“ refers to central Europe) is Gamblin PVA size. I suppose you tested PVA size (whether Gamblin or something comparable), can you tell me, how does it compare to GAC 100 or FMM? For example:
1. In terms of drying speed, leveling, brushability,
2. Will it dry to surface of similar hardness? One time I tried vinyl acetate ethylene size and even when it was dried it felt slightly sticky to the touch.
3. Is it possible to sand dried PVA size or rub with pumice stone as it is possible with GAC or FMM?
4. Do acrylic primers adhere well onto PVA size?
Best regards
Ivan
HI Ivan,
I like applying Gesso directly onto medium weave linen with a trowel. I use a plastic trowel with softened corners and knife the Gesso smooth. Sometimes if there is a knot, the knife will skip, creating a little chatter, but those can be removed by cleaning off the blade and skimming perpendicular. 3-4 coats like that can give a smooth surface without raised fibers from the fabric. If you wanted to sand off any nubs between coats, that would be fine, but it may scuff back into the surface which would then need to be coated with additional product to block oil. Using a blade to apply Gesso also helps to get the product onto the surface fast, removing any issues with fast drying.
We recommend 3 days dry time because that is how long it takes for the vast majority of water to evacuate the product. We have applied oil ground over acrylic products after different dry times including several months all the way to the same day, and have not seen noticeable differences in performance. For this testing, we used many surfaces with gloss acrylic that were cured for years and they produced same type of results as working oils over fresh gloss products.
As for PVA. It was the Gamblin product we tested, though we did not test it under Gesso as a size prior to the gesso layers. It is very thin and water like. It dries at a similar rate to water. It soaks into the fabric and does not create much of a build. But, it may stiffen the knots on your linen enough that you can then come over to sand the nubs from the surface. From our limited testing, it does appear that acrylic gesso adheres to PVA sized canvas.
We hope this helps!
Take care,
Greg
Thanks for the useful information. Can you tell me if this study applies to water-soluble oils? I prep my canvas with 2 or 3 coats of acrylic gesso, and do the underpainting in acrylic washes. I then work in water-soluble oils, starting with paint that has been thinned with linseed oil or a ‘painting medium’, and gradually build up slightly thicker layers – but never impasto. I’m just curious if you tested water-soluble oil paints. Thanks again!
Hello Adrian,
Thank you for your comment. We have tested some water-miscible oils since publishing this article and have seen good results. We only have 2 brands in house with limited colors, but none of the colors showed signs of cracking over gloss acrylic medium, which is worst case scenario. There should be much less likelihood of a problem over acrylic colors, AND the fact you are adding oil to the initial layers, should put you into the safe zone. If you have not seen any issues, then your combination may be good to go.
Hope that helps!
Greg
I love Justpaint! I have never seen any comments on Michael Harding’s Non-absorbent Acrylic Primer. I usually use 2 layers over a commercially primed canvas. I like that my colors don’t sink in and remain vibrant. I use to have to do some oiling out. The oil paint takes longer to dry or so it seems to me. Harding claims there is enough tooth for the paint to adhere to. What do you think? Does Golden have a similar product? Best, Mark
Hello Mark,
Thanks for your comment. We have not tested that product yet. It seems very Gesso-like. As mentioned in the article, we have not seen issues with Gesso or Molding Paste. It seems the more solids in the form or pigments, fillers and calcium carbonate that are in a product, the better they perform in regards to this phenomenon. In general, if you are not seeing issues with your current combination of materials, then it may be totally fine. Moving forward, we will have to take a look at that and may do a follow up article with some of the suggestions we are receiving in the comments etc.
Best Wishes,
Greg
Hi Greg!
I have a question about how one would approach “clear” gesso/ground based on these new recommendations. Recently my paintings involve applying two layers of gac 100 onto canvas or linen (for SID protection), followed by two layers of fluid matte medium, so that the color of the natural canvas shows through. I then apply oil paint over this layer.
According to these new tests, what would you suggest for a clear ground that results in minimal cracking? Should I avoid gac 100 entirely, even if its applied underneath the matte medium? Does matte medium itself provide some protection against support induced discoloration?
I’ve also heard people use PVA size on canvas as a clear ground, but I’m worried about oil strikethrough and the oils eventually damaging the canvas.
Thanks!
Audrey
Hi Audrey,
Thank you for your question. The first step to avoiding this issue is to remove the GAC 100 from your process. While this may slightly change the way your initial layer of Fluid Matte Medium applies to the surface, it will take the gloss acrylic out of the system, which is a step in the right direction. Three coats of Fluid Matte Medium should block oil penetration into the fabric (two coats actually block, but might apply another just to be sure). Because we have seen cracking over Fluid Matte Medium, we still recommend adding some oil or medium to your colors. 5% stand oil or alkyd medium or 10% linseed oil seems to be enough to mitigate issues over gloss acrylic in our testing. Do you tend to add any medium to your paints?
We have not seen any cracking over PVA Size, but it can allow strike through with oily or slow dry colors. Three coats should be good in most cases.
We hope this helps!
Greg
This is very helpful, thank you! I do usually add medium to my paints – if I understand correctly, is it better to use a fat medium rather than a more neutral or lean medium (like a 50/50 mix of linseed oil and mineral spirits?)
Hi Audrey,
You are welcome! It depends what kind of acrylic product you are painting over. Do you work in oils directly over Gesso or do you use an acrylic underpainting, clear gesso or other type of acrylic product? We are recommending removing any type of glossy medium or gel from the painting.
Over Gesso, simply do whatever you want. We found no way to create this type of cracking over Gesso. Over most other acrylic products we are recommending oil additions. We tested oils without solvent and an alkyd medium that has about 50% solvent. We did not test 50/50 linseed and mineral spirits. But a couple things come to mind- solvent evaporates out of the layer which means if one uses 50/50 solvent to oil, then it would require twice as much medium to get to the ratio we found provides benefit. Also, because the solvent evaporates, it will leave a thinner film, so may not reach the thickness threshold where the cracking begins to appear.
Have you ever seen cracking in your initial oil layers with your current technique? If not, then you may be fine to continue as you are…Let us know.
Best,
Greg
If one is underpainting with acrylics, is it better to use your So Flat (or mix regular acrylics with matte medium) instead of using a glossier acrylic?
Hi Lori,
We found no cracking in oil layers over SoFlat. But, because they are absorbent, the oil from the application can wick into the SoFlat and leave an oil halo around the oil paint. This is not an issue if you are covering the whole surface, but it might still be good to add a small amount of oil to compensate for the absorbency of the SoFlat. Natural fiber supports should still be prepared with 3 coats of Acrylic Gesso before using SoFlat for underpainting oils. We did not test different levels of Matte Medium into regular acrylic colors to see if there was improved performance. We found that both had the capacity to cause cracking, so recommend adding 5-10% oil or medium to any oil colors applied over either or both of those acrylic products.
We hope this helps!
Greg
Hello ,Greg
I have an issue to need to be confirm , Using Acrylic Gesso ,is it Brush better than blade/trowel ? i think it is better ,Cause when brush after 3 coats you still can see the texture/fiber of the linen weave / Knots , after Acrylic Gesso 3 coats ,you can use blade/trowel apply one or two coats of oil ground to make the surface plain/flat . this will better for oil adhesion ?
Brush the Acrylic Gesso will have more texture/ Knots on Linen Canvas , it will create more good adhesion to Oil , Am i right ?
i do not care the surface plain/ evenness/smooth ,cause i do not draw old classic or Hyperrealism . I only care to create the maximum adhesion of oil over Acrylic . Any guidelines to create Maximum adhesion ?
and one more more thing need help ,i am in China ,there are Golden Acrylic Gesso for sell here ,But i am afraid it may produced years ago , May i know when is the expiration date for Acrylic Gesso ? And also for Golden Oil colors what is the expiry date ?
Many Thanks !
Hi Gavin,
Thank you for your question. Brushing the gesso is a fine way to go. We have not seen a difference in the performance either way in terms of adhesion, but having a little more texture to apply the Oil Ground should deposit a slightly thicker layer and, as you mention, it is possible to use a blade with the Oil Ground to get a nice smooth application if desired. Our Gesso product does not have a shelf life. But, it can separate a clear liquid on the top after sitting for a while. Simply shake and/or stir that back in before use and should be fine!
Hope this helps.
Greg
Hi Greg, The cracking issue of oil paints over acrylic mediums such as the GAC Product Line recently came to my attention and enjoyed the FB presentation on this. As a gold leaf gilding teacher I often have conversations with students who, as oil painters, often wish to paint over gold or other metal leaf, some which may tarnish in time. The conventional wisdom in very recent years has been to apply your msa varnish over leaf that has been gilded on either canvas or a panel. The msa protects the leaf, especially the tarnishable ones. To protect the varnish the idea is to apply GAC 200 over the varnished leaf if on a panel and a 50/50 mix of the GAC 200/500 if on a canvas. With the proper drying time this would allow painting with either oils or acrylics with the GAC acting as an isolating coat for overall protection of the leaf during future cleanings.
However, now with the evidence of cracking of oil paint over acrylics I am wondering what isolating coat you might now recommend or is the research into this still too early to tell? Do you feel the added 5-10% of oil to the oil paint would be enough to go into the ‘safezone’ that you mentioned? And if so, would the added oil need to take place throughout the entire process of the painting in all its layers?
Thank you for helping to address these issues Greg, a very interesting and valuable Blog you have here!
~ Charles
Hello Charles,
Thank you for your comment and questions! There are certain techniques like the one you describe that make it difficult to avoid using oils over gloss acrylic mediums. If there was no alternative but to work over these products, then adding medium or oil to the paint is our best suggestion. If the initial layer of oil had the 5-10% additions, then yes, that amount or more should be used in subsequent layers to maintain the traditional fat over lean rule. Keep in mind, that not all oil colors display a propensity for this type of cracking, so the oil addition is a precautionary measure. It can be mentioned to your students that if they have not seen any issues with this combination of materials in the past with the oils they use, then its likely they may not see this issue moving forward. As an extra step, Acrylic Gesso can be applied over the GAC in the areas where oil paint will be. We found that 3-4 coats blocked this cracking tendency even in worst case scenarios. So if the texture and thickness would not be an issue, then that should help prevent the possibility of cracking, especially if folks want to use lean paint.
Alternatively, the areas where paint will be applied to the surface can be left ungilded. With just Acrylic Gesso or another appropriate ground applied, and then the oils can overlap the gilding slightly.
While it does not seem to be part of your proposed technique, I just wanted to remind you that we do not recommend painting with oils over the MSA either, as we have seen the varnish soften when oils are applied over top and cause drying defects in the oils. Here is another article that describes that issue: https://justpaint.org/why-oil-painting-over-msa-or-archival-varnish-is-not-recommended/
We hope this helps Charles. You can follow up with any more questions at gwatson@goldenpaints.com
Best wishes,
Greg
Thank you Greg for your thorough and thoughtful response to my questions on painting and gilding. Today where artists may be using tarnishable metals, acrylics, oils, oil size, acrylic water -based size we certainly have a cacophony of materials needing to work in tandem – quite a challenge! So I appreciate your input as I help others in the realm of gilding. And thank you for your email as well and I look forward to speaking again.
I have actually just read the article you mentioned on not painting with oils over MSA. I’m finding other difficulties where some students from other countries have difficulty in acquiring the Golden products. But everyone’s creativity and curiosity will go a long way in solving the dilemmas that come up.
Thanks again!
~ Charles
You are very welcome Charles! It sounds like your students and colleagues have a very contentious guide! Good luck with everything and please keep us in the loop about what you find is working well for you. We are excited to continue learning!
Take care,
Greg
Hello Greg,
I’ve just started oil painting, and I’ve prepared my panels for painting as follows:
-Braced 48”x 64”poplar plywood panel sealed on both sides with GAC 100
-Linen or cotton canvas mounted and thoroughly sized with GAC 100 (applied in one step with a roller and a wide knife)
-Canvas primed with two coats of acrylic gesso thinned with 1/3 water
-I’ve underpainted with (mostly) thin washes of acrylic paint (occasionally somewhat thicker)
-Followed with thin but heavily worked oil paint, often slightly thinned with linseed oil and, early on, a little mineral spirits.
Should GAC 100 be avoided in this circumstance? I’ve used it to prevent Support Induced Discoloration and to adhere the fabric to the plywood support. One source (Gottsegen, The Painter’s Handbook) advises that PVA will be too soft to use as a substitute. Do you have a reccomendation for what I could instead use?
Also, a somewhat related question: Are Golden Open slow drying acrylic colors suitable for over painting with oil paints (subject to the same qualifications as other acrylic paints)?
Thanks, and thank you for your thorough and clearly written advice!
Bill
Hello Bill,
Thanks for your questions. It sounds from your description that everything looks good. If the oils have been applied over the acrylic layers without any issue, then great. We have been communicating with artists like yourself who have used GAC 100 under oil colors for years without any issues. It is a possibility that this type of cracking can occur, not an inevitability. That said, you might reduce the risk further by using Matte Medium or Soft Gel Matte instead of GAC 100 for adhering the fabric to the panel and reducing absorbency of the surface. While we did see the potential for cracking directly over these more matte products with lean oil paint, the potential was much less than over glossy acrylic mediums like GAC 100. The Addition of Gesso layers should help reduce the potential further yet. And it is not really necessary to protect from SID when working in oil layers. Oil paints will not activate the water-soluble colorants which cause SID. The Gesso might, but the layers are thin and dry fast, so, less of a concern than thicker acrylic applications or slow dry acrylics.
Speaking of slow dry acrylics, it is possible to paint oils over OPEN as you would regular drying acrylics. We recommend allowing about 30 days for the OPEN to dry before proceeding with oils. It does take that long for the volatile materials and moisture to evacuate the film. As mentioned the OPEN would be subject to the same qualifications as regular acrylics in regard to oil / medium additions to oil paint layers applied over top.
We hope this helps. Good luck with your oil painting. Any other questions can be directed to our help line – 800-959-6543 or help@goldenpaints.com. You can ask for me if you like.
Best,
Greg
Hello greg
Thanks a lot for your sharing ! seems Acrylic will help to provide permanent preservation of oil base against RSG ,
but another issue is the canvas , any suggestion on how to protect canvas ? can i apply both sides of canvas with Acrylic ? i mean both face and back side of the canvas ? so the canvas will be sealed from air to prevent from rotting . and i read some articles , some suggest use Calcium hydroxide with water to spray on canvas and wait it dry ,leave the Calcium hydroxide on canvas for Deacidification ,to prevent long term Acid erosion . Are this two measures workable ? thanks !
Hello Zoey,
We have seen good results with some acrylic products under oil paints. Acrylic Gesso and Molding Paste both seem stable as a base for oil. We have not done too much testing with applying acrylic to both sides of fabric to protect the fibers from breaking down. That would likely be a long term test that might span several careers here at Golden, as it takes several decades for cotton to begin to deteriorate and linen even longer. Be cautious to apply an even coat on the front and back. Uneven coatings can cause variable tension that can cause the fabric to buckle. There are different grades of polyester fabric on the market that should be rot resistant and function similarly to natural fabrics. and As for Calcium hydroxide, that is also something we have not looked into. It sounds like it may act as an acid buffer, not unlike some papers that are acidic but have PH buffers such as a calcium additives to keep them from degrading too quickly.
Sorry no definitive answers for you, but all good investigations that we may be able to address at some point in the future.
Take care,
Greg
Hello Greg,
Thanks for the article!
About your ”Preparations for oil ground”.
Can we replace the gloss medium for 2-3 coats of PVA size on wooden panel before paint with oil painting?
I search for the best transparent ground.
Thank you so much!
Hello Sybiline,
you are welcome and thank you!
Yes, you should be able to prepare wooden panels with a couple coats of PVA before oil paint. Or, if you dilute your initial oil paint layers with 10% or more of medium with or without solvent, then you can use something like Fluid Matte Medium. 2 coats is usually fine to prepare panels. We saw minimal issue over this product with lean oil colors, and it should mitigate any cracking effects if there is medium added into the paints.
Best wishes,
Greg
Hi,
I’m using linen, stretch it first, size it, then add 2 layers of oil ground. Last but not least, I glue the dried canvas onto an aluminum panel with a PVA glue. I would like to have good oil blocking properties. I’ve been thinking about getting RSG. It for sure will have less deleterious effect on the painting given the rigid support, but it can still soften (I think) and maybe move a little bit with very high humidity? PVA is another option but I’ve heard that it’s not good at oil blocking. With regards to acrylic grounds, it’s probably a more expensive option and I’m kind of wary of it honestly. I try to keep it simple and not too expensive, therefore I’m leaning towards RSG.
If you were me, what would you size your canvas with?
Thanks,
Peter
Hello Peter,
It sounds like you are already sizing with PVA before your oil ground application.? If this is the case, then perhaps you should stick with that, especially if you are using the same material to adhere the canvas to the panel. The fewer types of material in the structure of the painting, the better. That way you do not have many different materials aging differently and being influenced by environmental factors differently as well. An alternative would be to size/prime the canvas with 3 coats of white acrylic gesso before the oil ground and use an acrylic gel to adhere to the panel. Here is a link to a video showing the use of Soft Gel to adhere paper to panel. You could use the same technique to adhere canvas to panel: https://www.goldenpaints.com/videos/applying-paper-to-boardadhering-watercolor-paper-to-panel-using-golden-soft-gel
We have seen slightly variable results with PVA in terms of oil penetration. We test with 3 drops of refined linseed oil directly onto the prepared canvas. With PVA we see it takes 3-4 coats to block straight oil. This is a very rigorous test, as most grounds or colors dry much faster and are less likely to strike through. This is particularly true if you are using an alkyd based ground which should dry overnight. For most applications, 3 coats of PVA should be fine.
In general if there is not a specific reason to use the RSG, then we recommend keeping it out of the system.
We hope this helps!
Greg
This is super helpful. Thank you. Watched your video too. I have two questions.
1. What were the results of testing oil and wax? Oil sticks?
2. When you refer to “aggregate pastes and gels” do you mean mixtures of various acrylic products? I’m wondering what happens if one mixes acrylic colors with gloss gels – still a problem? This is the sentence I’m referring to: “Satin, semi-gloss and matte acrylic mediums, acrylic colors, and aggregate pastes and gels can be associated with minimal or microscopic cracking in oil layers.”
Thank you in advance
Hi Anna,
Thanks for your questions. 1. We did not see any issues with the oil sticks we tested over gloss acrylic mediums. Our testing was limited to about a half dozen sticks, but the results were good. Oil sticks tend to have fairly high percentage of oil and wax compared to regular oil paint, so that could be why they seem resistant to this issue. Additions of Cold Wax Medium did show some cracking over gloss acrylic. We added about 5 and 10% and still saw some minute issues, so will have to go back to that at some point. Keep in mind, both of these options should be fine over Acrylic Gesso. 2. Aggregate gels are any of the gritty gels that have obvious large particle materials that provide some texture: Pastel Ground, Pumice Gels and Fiber Paste all are aggregate gels. We only saw issues at the microscopic level with these products and only with a select group of oil colors. We did not see issue on the Molding Pastes that are appropriate for oil painting over (exception being Light Molding Paste which is too spongy for oils).
We hope this helps. Please let us know if you have additional questions at help@goldenpaints.com or email me directly at Gwatson@goldenpaints.com
Thanks
Greg
That is super helpful. Thank you so much, Greg. I’ve been using pastel ground between acrylic underpaintings and final oil layers, and never had any problems – consistent with your research. Thank you!
That is good to hear Anna. Keep an eye out and let us know if you ever see anything. Otherwise, best wishes in the studio and take care!
Greg
A hypothesis on what may be the underlying cause behind this occurrence. We know gloss surfaces have less absorption than matt surfaces. Matt surfaces absorb and emit heat more effectively, while gloss surfaces are poor conductors. Since oils dry through oxidation, which produces heat, the poor conductivity of the gloss surface may be preventing or interfering with the oxidation of the paint film. By adding more oil in the form of mediums, you’re strengthening the paint film and increasing its flexibility, making cracking less likely to occur. Looking forward to learning what you discover is the cause.
HI Jeff,
Thanks for thinking this through. There are certainly several factors contributing to this phenomenon. We are still at the early stages of working with our conservation partners to fully understand the mechanisms behind the issue. But, appreciate your thoughts and enthusiasm! It is exciting! We will let you know once we learn more.
Best,
Greg
Regarding when Painting with Oils on Wood panel:
Hi,
what do you recommend in place of golden gloss medium to prevent SID before the three layers of acrylic gesso on a wood panel? Or is the three layers of acrylic gesso (as one of the recommendations above) enough to protect from SID when painting over wood?
Thanks,
Isabelle
Hello Isabelle,
Thanks for your question. Fortunately, SID is only an issue that affects acrylic or other water-based paints. It’s the water in these products that leaches into the wood, activates the colored impurities, then gets drawn back up into the paint layer upon drying through evaporation. Oil Paints dry through chemical reaction, so do not cause SID. Gloss Medium is not needed when preparing your panels for oils. You should be good to go with 3 coats of Acrylic Gesso.
Hope this helps!
Greg
Hello Greg,
as you can tell I primarily use Golden Acrylics, but wanted to branch over into oils as well…
Thanks for the feedback, now I feel secure in how to prepare my paint surface!
Best,
Isabelle
You are welcome Isabelle. Best wishes!
Greg
Hi Greg, I have a question about the chart Acrylic ground for oil painting – Preparations for oil ground: are the white sections meant as alternatives (professional acrylic gesso OR GOLDEN Molding Paste) or one should superimpose all the products mentioned (professional acrylic gesso AND GOLDEN Molding Paste)? Thanks.
Davide, Italy
Ciao Davide,
Thanks for your clarifying question. Each product recommendation in the rows / white section can be used independently of the other. So, either 3 or more coats of Acrylics Gesso, OR 3 or more coats of Molding Paste, OR 2 or more coats of GOLDEN Sandable Hard Gesso on panel etc… These recommendations should be sufficient to block oil penetration and prepare the fabric or panel for Oil Ground or oil painting.
Good luck with everything. Let us knw if you have additional questions.
Greg
Hi Greg,
thanks for this report and this raises a good warning for artist. i am afraid will we isolate one issue but introduce a new issue by just taking out glossy size medium?
for instance, what is the purpose people recommend to size wood panel first before acrylic gesso before? i guess since gesso is a very porous surface, the size medium build an isolation layer there. so w/o isolation layer, will the oil sink into wood that causes oil paint unbond later? or will the wood tannins and lignin migrate back into oil layers?
also, SID is problem for acrylic if not sized, then w/o size layer, will SID affect white acrylic gesso to make it darken? if the gesso ground is darken = oil painting affected by SID indirectly
Hello,
It is possible that changing one’s preparation may slightly adjust the absorbency or performance of a surface. But, it should not be so different that the structure of the painting will become vulnerable to failure. We have tested Acrylic Gesso under oils in many trials and found it to be a stable surface for oil colors. While it is porous and toothy, it is not so absorbent that it will draw excessive amount of oil from the layers and leave them underbound. The inclusion of GAC 100 or Gloss Medium under Gesso on a panel is carried over from acrylic painters preparing their surfaces to block SID. This is not a concern with oils, as the paints do not interact with the panel and water soluble colorants in the wood the same way that acrylics do. SID is exclusively an acrylic issue. While the Gesso on some wood panels might darken slightly due to SID, It should not change after it is dry, and will not darken over time and effect the color of the oil layers. We do not have any testing that shows tannins or lignin migrating through acrylic layers, including Gesso, into oil paint layers.
We hope this helps to clarify.
Greg
I’ve read and reread this a ton. I even watched the video several times. Thanks so much. I have just started experimenting with acrylic under my oil painting and letting it show at times. Can you paint in oil over acrylic pour painting? I understand they use a silicone product to get those lacy cells to appear. I am wanting that effect for a first layer before oils, but I think that is a very wasteful process. SOOO much paint used. Is there anyway to get that kind of effect without so much paint and still be archival for oil painting on top? I am wanting to do a series about the environment with effects that look like ice and water as a background that I can paint on top of with oil. I am using cradled gesso boards that are commercially prepared for all media. Does the addition of metallics in the acrylic layer affect it in anyway? Also you are freaking me out about the zinc. I had never really thought about it. I use MGraham and Gamblin titanium white and they both have zinc in them. Do you consider those paints zinc “rich?” I read on the Mgraham site that they do it to avoid the stringiness of titantium. Thanks so much.
Hi Tracey,
Thanks for your comments. It looks like Mike addressed some of your questions regarding oils over acrylic pours. While it is possible to layer in this way, adding oil or oil medium to the oil color is recommended to mitigate the potential for cracking. We recommend 5-10% oil additions. That is basically a drop of oil for a pea sized piece of color, or roughly there about. You might also be able to try to create some similar look to the acrylic pour with oil paint and some solvent and/or fast drying alkyd medium. This is something that can be tested directly onto a Gessoed canvas or panel.
As for the zinc issue, this is something that has been known since the very early days of zinc pigment being available. It simply reacts with the oil and creates a harder film than most other pigments. This can lead to embrittlement or cracking. While all oil paint layers will eventually become brittle over decades, oil paint with zinc can become brittle over just a few years. Often the zinc additions in white help to provide a brighter white than just the titanium or zinc can provide on their own. Also zinc helps to provide a buttery consistency, which is what MGraham mentioned. We recommend avoiding zinc where possible, but if it is used, then consider in the upper layers of the painting, painting on panel, and adding some stand oil or other bodied oil to the paint layer if possible.
We hope this helps!
Greg
Thanks Greg. It seems like adding oil to the oil paint is going to need to be done no mater what I use in my acrylic layer. I can handle that. I do not see how or where Mike addressed my question about oils over acrylic pours, where can I find that? I did find an artist on youtube who did a much more moderate use of paint pour technique – Linda Celestian and the video title has “Ice Ice Baby” in it in case you are curious. She thinned the paints with your airbrush medium. This was many years ago and I’m not sure you still make that. She then put saran wrap on top to artistically have the pigment gathered in the creases creating an ice look. It is a very thin wash over previous layers. I think this technique is exactly what I am looking for but what medium should I use? For that matter what paints? Your fluid line? Thanks so much!
I’ve been experimenting with Golden’s fiber paste as a textured ground under oil paint. I called Golden and they advised using a little extra oil in my paints. I’m curious if it would further prevent cracking to also apply a thin coat of gesso over top of the paste before applying oil paint. Do you have thoughts on this? I’m only interested in the fiber paste because of the textural qualities so the color doesn’t matter.
Hello Lydia,
Yes, we found adding Gesso over problematic surfaces definitely helps. The Fiber Paste was just on the edge of having issues, so a coat of Gesso and a little oil in the paints should get you into a safe zone.
Let us know how it goes!
Greg
I’ve been painting oil over acrylic ground for years with no problem, thankfully. One thing I do is wait a couple days for the acrylic to dry and a day before , I carefully wipe the surface with a pretty wet rag. There is a very distinct soapy film that I assume are surfactants that have risen to the surface, and so I wonder if this film could be contributing to the test’s cracking/crazing issues?? It usually takes me a a few water soaked paper towels to rinse off the soapy layer. I never really knew much about this issue, but when i discovered it by accident years ago , I figured it would be best to remove that film before painting in oil.
Hi Joe,
That is good news. If you have not seen cracking with your technique, then perhaps you will not come across it with your particular process. That residue is likely surfactants. It is not a bad policy to wash those off before using oils over acrylic. They can sometimes congregate on the surface and make a slightly speckled effect that can show through some oil applications. We did test wiping down with water to remove surfactants on several of our test surfaces. Where the cracking was present, the wiping did not improve the situation in any significant way. That said, it may benefit in some cases, as we certainly did not test wiping on all our surfaces. What type of products are you using for your acrylic ground or underlayers?
Happy you are having success!
Greg
Hello Greg,
I am so grateful for this website. I am a long time user and lover of Golden’s Matte Medium. It is especially fortunate then that your research seems to support Matte Medium as superior to other acrylic gels. I have been using it to create collages, thickly layered, often with paper embedded, and without support underneath. This is intentional as I like the edges curling. Most of my current work is smaller, around 5″ H X 7″ W, and now I’d like to add color in glazes, with oil paint however, thin layers of pigment mixed with cold wax medium and good quality cold pressed linseed oil.
So do you think this will hold up, without the support underneath, and just with the layers of Matte Medium under the paint?
PS. If you trouble yourself and the time you have, you can see previous collages that I’ve done on my website; the photo imagery is poor so you won’t see the actual 3D quality but you’ll get an idea.
Thanks, Bobby Vilinsky
Hello Bobby,
It is difficult to say whether the works will hold up. If they are cared for, then they may last for many years or decades! In general, we have found that 2 layers of Matte Medium should keep any oil applications from soaking into the paper, which will help with longevity. Also, while we did see some cracking of lean oils paints over Matte Medium, it is unlikely that you will see any issues if you are making glazes with oil medium and cold wax. Very translucent applications should not crack due to this phenomenon.
Best wishes with your works and thanks for your comment!
Greg
Is it fine to apply an oil ground such as Gamblin over a store bought, pre-acrylic primed canvas for oil paintings?
I buy the pre primed canvas and apply an oil ground for oils and a matte medium for acrylics.
Hi Jody,
It should be fine to use pre-primed canvases for oil painting or oil ground application as long as the brand specifies that the canvas has been prepared for that use. We typically recommend 3 coats of Acrylic Gesso to block oil penetration into fabric supports. If your pre-primed only has 2 coats of universal primer, then perhaps a third would be prudent before starting in on your oil layers. Let that dry for 3 days, then the oil ground can be applied over top. Your additional coat of Matte Medium as preparation before acrylic painting sounds good! We hope it all goes well. Let us know if you need anything else.
Greg
Acrylics begin to change as they cure, and dry over time, unless you have waited at least once month for the medium to get to a stable state of this process, the initial movement of the acrylic will affect your paint layers, and the difference in movement will delaminate the paint films from one another if there is not sufficient cohesion between them. This movement will crack the oil, and that is the least of the deeper problem. Different brands and types of acrylic product will have differing rates at which they dry out, making this pretty hard to gauge, but waiting at least 24 hours to paint over any acrylic is what most artist like to use as “good advice”. In my experience, unless you wait one week, you are at risk for some movement issues overlapping the cure of the oil vs the acrylic, remember, once coated with oil, the acrylic’s rate of cure will be affected as well.
To add a personal experience to this, I once used a normal acrylic paint (Latex, probably an eggshell) in place of traditional gesso. I have several canvas paintings to this day that I used this practice on. I showed my artwork at a local art event, and upon moving it, I accidentally bent the canvas with my knuckles from the backside of the canvas, holding the frame. The dried oil popped right off! Cracks around where I held the canvas formed, and other than the lack of air between the two layers, there was absolutely nothing holding the two together other than vacuum. This was after only one year! That was in 1991. The painting was 24″x 48, and was ruined, I had several chunks the size of jigsaw puzzle pieces that just fell out of place. This led me to doing two things: one, I began to use panels instead of canvas, for increased rigidity, and second, I changed to using a traditional gesso.
Hi Chris,
Thanks for your comment. In general, most of the drying in a normal thickness, acrylic film takes place in the first 3 days or so. We typically recommend waiting at least 3 days for acrylic to dry before working over top in oils. Waiting longer is fine too, because as you suggest, it can take many weeks even months for the acrylic film to fully coalesce and there can be shrinking during that time, especially if it is a thicker film. That said, we have tested oil paints on acrylic products that were dried for 1 day, 1 week, 1 month and found little difference between their performance in terms of adhesion, cracking or yellowing. in fact, we have rarely seen an issue with adhesion between oil paints and artist acrylic layers underneath. The oils tend to key into the acrylic surface very well regardless of the acrylic product. This cracking phenomenon we write about didn’t coincide with any type of adhesion issues.
Your experience with house paint may be pointing to a different issue, as house paints tend to be quite a bit harder than artist acrylics. House paint manufacturers do not have to worry about flexibility and one of their primary concerns is opacity, so the solids/binder ratio might be a bit higher than in artist acrylics or Acrylic gesso. Also, zinc content in oil layers can cause a similar type of embrittlement and delamination to what you describe. Often color blends and some titanium whites contain zinc oxide PW4, which can cause such issues. Refraining from zinc oxide and using a high quality Acrylic Gesso as a ground should provide stable results if you ever wanted to get back to working on canvas.
Take care,
Greg
Hi Greg
I’m not sure if this feed is still open but thank you so much for all of this research, I have read through most of the comments so I apologise if this has been repeated but I couldn’t find this particular question.
With GAC 100 on board (mdf/plywood), would manually giving the glossy surface a key by gently using sandpaper have any effect on the cracking phenomena? (If then using oil paint directly on top of this keyed surface)
I know the question seems arbitrary and would make more sense to use the aforementioned PVA or even matt acrylic medium, it’s only that I have quite a lot of GAC 100 left over and do not want to waste it if possible.
I duly take note of adding 10% medium to the oil paint applied on top.
Kind regards
Hi Eifion,
Thanks for your comment. We tested scuffing glossy acrylics with different grit sand paper and even with different scuffing patterns and did not find it to alleviate the problem. It did change the cracking pattern to a fine, regular craquelure, which was interesting. But, it did not eliminate the issue. As you mention, if you work over GAC 100, adding additional medium to your color should help!
Best wishes
Greg