Set yourself up for what you want to do with the pastel. For example, if I want to paint the shadow shapes, I’ll underpaint lighter, and so on. Many artists use complementary color choices in an underpainting to add luminosity to the finished painting. I like to use this in some areas and go for the local color in others.
Over the years I’ve experimented with many underpainting techniques for my pastel paintings, which has led to my current method of working on a sanded pastel surface. I begin with a drawing, followed by a loose, wet underpainting. My favorite underpainting methods are: pastel spread with water; watercolor; or washes of oil paint, thinned with mineral spirits. Each method has its advantages and disadvantages. Since liquid swells most surfaces, I work on pre-mounted paper or a very rigid prepared surface.
Here’s an exercise I like to give students to strengthen their intuition when making choices for underpaintings: Select a subject you have painted many times—not something intimidating or new. Work up a series of small paintings of this subject using different underpaintings. Start with one on a black surface, then a white surface, a mid-value warm orange surface, and a mid-value cool, blue/violet surface. After working on these flat-toned surfaces, try painting the same subject by blocking in major areas, utilizing color and value variations. Working on a white surface, do an underpainting in which you work with only a warm and cool tone, such as burnt sienna and ultramarine blue; then another in which you utilize opposite colors under the major color masses, such as a rose color under the blue sky; and finally, an underpainting in which you paint however you please.
When it comes to these choices, it’s up to each artist to find his or her own personal voice. By trying many things—and going through a lot of product!—you’ll have a stronger intuition the next time you decide to underpaint.
I used a black surface for Saffron Crowns (pastel on grit board, 16×20) above.