Producing a wet underpainting with pastel is something many paitners have experimented with. Personally, I enjoy doing a watercolor underpainting when working en plein air, because of the immediacy and simplicity of opening a small watercolor palette, dipping a brush into a little water, and letting it go. In the studio, on the other hand, I often turn to thin washes of oil paint, using a large amount of mineral spirits. In both cases, it’s important to select a paper that can withstand the process. Wallis sanded pastel paper or the new Uart premium pastel paper are good choices.
If you choose to use pastel to produce a wet, drippy, runny effect (similar to what watercolor and oil create), I do have a few tips:
- Know your surface. Can it accept certain solutions without a problem? If water is to be employed, then a ridged sturdy surface will be needed; otherwise, it will be prone to buckling. If mineral spirits are used, make sure it won’t soften the adhesive that was used to mount the paper. For these reasons, I generally stick to a simple rule, using water on mounted paper and mineral spirits for unmounted paper. Note: If the pastel paper was archival mounted using a pH-neutral heat adhesive or PVA acrylic adhesive, it’s fine to use mineral spirits. Rubbing alcohol has been another popular solvent, but I avoid it since most of our surfaces have an acrylic nature and may be softened—if not removed—with its use.
- Use bright pure pastels, avoiding sticks with white or black added. These “tinted” and “shaded” pastels often produce cloudy effects when spread. Think of your pastel choices as if they were tube pigments. If the underpainting is to have a translucent quality similar to a watercolor or glazed oil paint, the substrate should show through. The whiter and brighter it is, the stronger the diluted pastel pigment will appear.
- Test pastel brands (on the surface you plan to utilize) to see how they interact with water and mineral spirits. Many manufactures add inert products to their sticks to create a characteristic feel. These products can be water-resistant or gummy when made wet. The purer the pigment content, the less change will occur when dampened. Many of the current brands work very well, but I’ve found that Sennelier pastels stand out as a constant winner; their pastels are pure pigment with the tiniest amount of binder and no fillers added. These pure pigments are capable of brilliant underpaintings, producing less of a clouded/muddied appearance. Holbein also makes an interesting small set of water-soluble pastels. This tiny set of 24 colors is a joy to spread around when water is utilized. Try your favorite brand to see how it responds.
- Apply thin amounts of pastel. Don’t attempt to cover the entire surface. Too much pastel will create a paste and over-fuse the colors, creating mud. It’s advisable to start by wetting the lightest/brightest areas before proceeding to the darks. The darks can easily contaminate the lights and should be handled with care. Allow the darks to be a little lighter and more colorful. This produces a better underpainting, giving the shadows more depth.
Remember that an underpainting is just that, a setup for the pastel painting. Keep it thin and mysterious, allowing the pastel application to produce the resolve.