Painting Oils on top of Acrylic

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Painting Oils on top of Acrylic

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Painting and Photo by David Cunningham

Recently on social media, artist David Cunningham asked his online colleagues if any of them engage in acrylic underpainting as part of their oil painting process. Amid the discussion, David stated that while he loves the process–we was warned (by conservators) the process was a bad idea. So, as usual, we set out to see what the possible problems could be.

The most robust resource that we were able to find on this topic came from the Golden Artist Colors, Inc. website.

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In the technical section of their site they state:

OIL OVER ACRYLIC GROUNDS

A significant body of research in conservation science, and more than 40 years of actual use, has repeatedly proven that high quality acrylic gesso provides excellent adhesion for oil paints and can be considered a fully archival and suitable ground for oil painters to work on.

OIL OVER ACRYLIC PAINTS, GELS, and MEDIUMS

Evidence suggests that adhesion is rarely the issue when using oils over a wide range of acrylic products, and most oil paints should adhere well to the majority of our gels, paints, and mediums. Almost all acrylic paint films, regardless of sheen, are still porous enough to allow oils to penetrate sufficiently and form a reasonably strong bond. The real concern with oils is their tendency to crack as they become increasingly brittle and inflexible with age. This is true regardless of whether the oils are on top of acrylics or more traditional materials. Because of this, we do not recommend using oils over a very thick application or texture, of any material, without some concern. The reason is that these materials will likely change over time, as well as expand and contract in response to the environment, at a different rate then the more fragile oils can accommodate. Ultimately it is these factors, rather than the use of acrylics per se, that leads to the potential of cracking.

Golden Colors then goes on to state that you should follow some simple guidelines to lessen such risks:

Work on inflexible supports whenever possible.

Make sure all acrylic materials are completely dry and fully cured beforehand.

Maintain a matte surface.

Avoid using over soft, spongy materials.

Keep in a stable environment.

Avoid rolling or flexing when possible.

You can read the entire post from Golden Artists Inc., here:

https://www.goldenpaints.com/technicalinfo/technicalinfo_oil_over_acrylic?fbclid=IwAR2J8J6l377VCrEqfa02NWtQbrwwc67gxjHFgBv9jjGCwWQotbQsUD-oYRo

Contact info for Golden Artist Colors, Inc.:


Golden Artist Colors, Inc.
188 Bell Road
New Berlin, NY 13411-9527 USA
Toll Free: 800-959-6543
Fax: 607-847-6767
help@goldenpaints.com
www.goldenpaints.com

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Quite fascinating, Anthony. Thanks.

Just to point out David Cunningham’s actual reason for posting was that he found watered-down acrylic underpainting (applied like watercolour) helps boost the opacity of the oil paints applied on top.

I often work with an acrylic underpainting but haven’t really noticed. I feel some tests need to be done!!

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Thanks for the clarification Tom. If you have any experience with this process, I would love to hear your thoughts on it.

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Winsor & Newton’s article on painting oils over acrylics: http://www.winsornewton.com/na/discover/tips-and-techniques/acrylic-colour/acrylics-as-underpainting-layers-us

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Awesome—thanks Tom!

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If watering down acrylic, why not just use watercolour or can you not achieve enough density? I have been planning on trying just that for n underpainting though due to illness have not painted in about a month so alas have not had a chance to try.

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I’m sorry to learn that you’ve been dealing with some health issues Craig. I hope that you are feeling better ASAP!

As to using Watercolor instead of Acrylic—it seems that it would also work just fine. Here’s an excerpt from an article from Greg Watson for Golden Artist’s Just Paint website:

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Watercolor underpainting with 2 layers of oil paint made on oil paper. Oil paper is pre-sized to protect from oil penetration. Watercolor underpainting (left), oil paint thinned with solvent (center) and an additional layer of oil paint with added medium (right).

“Although watercolor under oil is not a widely used technique today, it is surprisingly effective and was well known, at least in the 19th century, among British painters (Carlyle, 2001). We found that regardless of whether the watercolor was soaked into the ground or dried over a glossy acrylic surface, that oil paint, medium and/or odorless mineral spirits could be applied on top without reactivating the watercolor. We tested QoR bound in Aquazol, as well as competitor brands made with gum arabic with the same positive results. We did not test watercolor over oil grounds, but historically it was practiced after the ground was deglossed and then properly cleaned to facilitate better wetting of the surface. Artists also used to mix ox gall into their watercolor to keep their washes from beading up. A benefit of watercolor is they can be reworked even after they dry, allowing artists to perfect an underpainting or wipe back to a bright white ground to establish the lighter areas of a composition. Unlike acrylics, watercolors do not require several days to completely dry and coalesce. They should be ready to paint over after they are fully dry to the touch. Here are a couple things to consider when using this technique:

The substrate still needs to be sized to protect from oil penetration. The exception being oil paper, which is already sized and prepared for oil paints. The watercolor layers do not count as sizing. Instead, prepare the substrate as if oils will be applied directly. In most cases, using watercolor in this way essentially amounts to making a mixed media piece with acrylics, watercolor and oils. It may benefit the watercolor application if the final layer of acrylic sizing or the acrylic ground is slightly absorbent.

Do not apply the watercolor thickly. The oil needs to be able to soak through the watercolor and bind to the substrate or ground. Thick applications could interfere with this important aspect of proper adhesion.

Do not isolate the watercolor from the oil paints with MSA or Archival Varnish. We have written many articles about the benefit of varnishing watercolors so they can be displayed without glass. This is great, but should not be used for this application because oil paints are not compatible over top of MSA or Archival Varnish. For more information see Why Oil Painting Over MSA or Archival Varnish Is Not Recommended.

Options for protecting exposed watercolor. Artists in the past optionally isolated their watercolor with a dilute natural resin varnish or very thin layer of light colored drying oil applied with a sponge. Although this might benefit an area of watercolor that is left exposed, it does not seem necessary to improve compatibility between the watercolor and the oil layers. This may have served a dual purpose of reducing absorbency of the ground and locking down the water sensitive paint layer. With this historical approach in mind, it may benefit to fully cover the watercolor underpainting with oils paints or at least glaze over all exposed watercolor to protect it from the potential of lifting. Alternatively, if after the oil painting is finished and there is still watercolor exposed, it can be varnished after the appropriate waiting period. We recommend allowing oils to cure for 6 months to a year before varnishing.”

Let us know if you try it!

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Have I missed something here? I understand that what is considered good practice apropos creating archival artworks varies, and that ultimately NOTHING is really archival.

It’s also possible I’ve misunderstood. But when The Golden Artist Colours says that:

Work on inflexible supports whenever possible.
Avoid using over soft, spongy materials. Does that rule out linen and canvas?

Maintain a matte surface. Does that mean don’t varnish?