Mixing Media
Is it safe?
I see the term "mixed media" on labels often when visiting galleries. Sometimes, the label elaborates, like "pen and ink with acrylic." I often wonder how these mixed media works will stand the test of time. Part of the answer has to do with 1) how compatible the media are and 2) the order of application.
Take, for example, acrylic and oil. Basically, this is oil and water—and as we all know, oil and water don't mix, at least not without a surfactant or dispersant like soap. I would never use acrylic and oil paint simultaneously in a painting as it would create a disastrously unstable layer. Here's why:
Incompatibility of bases: Acrylic is water-based, while oil paint is oil-based. These two mediums naturally repel each other, making it impossible to achieve a proper mixture.
Drying differences: Acrylic dries quickly through evaporation, while oil paint dries much more slowly through oxidation. When mixed, the acrylic components may dry faster, disrupting the oil's slower curing process, leading to an unstable, unpredictable result.
Structural integrity: Mixing the two can lead to poor adhesion, cracking, or separation over time, undermining the durability of your artwork.
So, as for actually mixing media together, I advise caution. When in doubt, always check with the manufacturers.
However, I might use different media in different layers, letting each layer dry before the application of the next one. For example, consider using acrylic as an underpainting for oil. Acrylic paint dries quickly and creates a sturdy, flexible, porous surface that oil paint can adhere to. In fact, many artists use acrylic for underpainting or blocking in large areas before applying oil.
But not all media work well this way. For example, I would never reverse the application in the case above and put acrylic over oil. Here's why:
Incompatible drying processes: Oil paint dries through oxidation, which creates a hard, less flexible surface. Acrylics, on the other hand, dry by evaporation and remain more flexible even after they cure. When acrylic paint is applied over oil, the flexible acrylic layer struggles to adhere to the rigid oil surface, leading to cracking or peeling over time.
Nonporous nature of oil paint: Once dry, oil paint forms a nonporous surface that makes it difficult for acrylic paint to stick. Acrylic requires a porous or slightly absorbent surface to bond properly.
Fat over lean rule: The "fat over lean" rule says that you should build layers from leaner (less oily) to fatter (more oily) materials. Acrylics are leaner, and oils are fatter, so reversing this order by painting acrylic over oil violates this principle, risking structural instability.
Many media, however, can be layered. Here are some general observations from my own experience that might be helpful:
Unless fixed, charcoal or pencil will smear and muddy or discolor media applied on top of it.
When applying water-based media over ink, use permanent ink so it doesn't bleed (unless you want this effect.)
As an underpainting for oil, acrylic is best applied thinly.
Oil and acrylic will act as a resist when water-based media is applied on top of them.
One can use liquid media (whether water- or oil-based) atop pastel, but unless fixed, the pastel will mix in with these media, possibly hurting the film integrity.
Gouache will liquefy if water-based media is applied on top of it. As with pastel, the stirred-up gouache might possibly hurt the film integrity of oil and acrylic.
Gouache applied on top of watercolor will generally reactivate the watercolor pigment somewhat.
Water-based media applied on top of casein will have no effect as, unlike gouache, casein once dried becomes impervious to water.
(I was in the midst of making a nifty chart with all the variations of mixed media, but it quickly become unwieldly because of the vast number of footnotes required for the many exceptions.)
My suggestion? Feel free to experiment, but learn how different media interact.
(By the way, if you’re a free subscriber, won’t you consider becoming a paid subscriber so you can read my latest series of posts on plein air painting, Primer for Plein Air. Only $5/month, and you can cancel anytime!)
Layered media is perhaps a better term than mixed media.