Ask the Experts: Technical Questions Answered for Artists
By Bradley Lance Moore
Insights on Water-Soluble Oils
Q. Can water-soluble oils be mixed with acrylics?
A. Introduced in the 1990s, water-soluble oils (WMOs) make up the third class of artist-quality, oil-based paint, the other two classes being alkyds and the more traditional oil formulations. Note that WMOs are considered water-reducible, not water-soluble.
Unlike acrylic dispersion, WMOs contain no water and aren’t a water-dispersed coating. But WMOs do have components that are compatible with both water and oil. Consequently, the properties of WMOs fall between those of solvent-and water-based paints. WMOs dry by oxidation, like conventional oils; thus, any added water can evaporate. To avoid compromising the water-reducibility of WMOs, you shouldn’t add them to traditional oils and mediums at more than a 30 percent ratio. Also, WMOs are better suited to acrylic-primed canvases than to oil or alkyd primings because added water increases the surface tension of an oil- or alkyd-primed surface, weakening the bond with the WMO.
To achieve the unique behavior of WMOs with water, manufacturers use soaps and other modifiers, and manufacturers aren’t usually forthcoming with their formulas. Furthermore, each brand uses different chemical compositions in its additive mediums, so mixing brands may lead to unpredictable results.
There are more than six brands of WMOs on the market today. While at least one brand (Winsor & Newton Artisan) says, “No!” to mixing with acrylics, another (Holbein Duo Aqua) says, “Yes!” Winsor & Newton states that its WMO “cannot be mixed with acrylics on the palette. However, it is possible to apply [the WMO] on top of acrylic, but never acrylic on top [of the WMO] …” In contrast, Holbein encourages blending its WMO with transparent watercolor, gouache and acrylic for a variety of effects. Holbein suggests adding a few drops of water when mixing its WMO with acrylic, to avoid separation of the two types of paint. Some artists use acrylic gloss mediums with Holbein WMO. The point here is that not all WMOs are alike; hence, reading the manufacturer’s warnings and recommendations is necessary. From there, you can conduct your own experiments.
Whether or not a given brand suggests mixing its WMO with acrylic, there are concerns about the long-term aging characteristics of WMOs versus acrylics. These two media function by totally different mechanisms, and results from tests on mixtures are not yet available.
Water-reducible: capable of being diluted with water
Water-soluble: capable of being dissolved in water
Find more “Ask the Experts” Q&As here! Bradley Lance Moore has both a master of science degree in painting conservation and a master of fine arts degree in painting. He teaches art history and studio art at the Maryland Institute College of Art in Baltimore and exhibits his artwork internationally. Visit his website at www.blancemoore.com.
MORE RESOURCES FOR ARTISTS