Breaking the Mixed-media Rules

Q. I recently experimented with painting acrylics on top of oils, and although I know it’s not a proper thing to do, the results look so good that I’d like to keep it. What can I do so that the painting remains stable as long as possible?
Hisham Zubari
Bahrain

A. Since the introduction of acrylic paints and grounds into the art world, experts have said that oils can be applied over acrylics but have cautioned against the reverse. When acrylics are applied over oils, it’s expected that the acrylic will dry first and then be cracked by the shifting of still-wet oil paint. Acrylic paints are typically found in emulsion form, meaning that the acrylic molecules are suspended in water, and the paint dries as the water evaporates—a relatively fast process. Oil paints, on the other hand, dry by a process of polymerization and oxidation that can take three to six months to complete, or even longer if the paint was applied thickly. Additionally, acrylic paints may have difficulty spreading evenly over and bonding to oils because the process is something like mixing oil and water.

Once acrylics have been laid over oils, however, as in your case, there’s very little you can do to increase the painting’s chances for long-term stability. If the piece has already completely dried without any obvious damage, then you’re off to a good start, but that doesn’t guarantee that the work won’t have adhesion problems in the future. The best you can do is what you’d do to protect any painting: Give it a proper framing, keep it in a stable environment, and avoid exposing it to extreme temperatures.

If you continue to experiment with acrylics over oils, follow the “fat-over-lean” rule of oil painting and never apply a lean layer of paint over a thick, oily one because the leaner layer will dry quicker and be likely to crack. Acrylics are really neither fat nor lean, but they are fast-drying. So keep your oil layer thin, and perhaps blot off some of the oil before you switch media to speed its drying time. Then let your oil paint dry thoroughly before adding the acrylic layers, and sand it lightly to give it some tooth, providing a surface for your acrylic to grab on to.

Ultimately, with a painting like this, you’ll just have to wait and see. Although you’re definitely taking chances with the painting’s longevity, I wouldn’t rule out success entirely. As a conservator, I’ve worked on many complex paintings in which it’s difficult to tell if the painting was done in oil, acrylic or a mixed technique without verification from the artist. So although it would be tough to confirm, I wouldn’t be surprised if there are a few acrylic-over-oil paintings out there that are already well past their life expectancy.

“I think you have to know the rules and then you have to have fun,” says Jean Pederson of painting in watercolor. “I was always the kid in school they asked to design the title page of the book or illustrate the poster, but my parents weren’t wil about my getting an M.F.A., so I got degrees in education as well.” A native Canadian, Pederson now teaches adult workshops “to get my teaching fix.”

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