Deciding to employ an underpainting is a matter of personal choice. Many artists work directly with pastel on a toned surface, while others choose to block in sections to create a substructure that they will then respond to with pastel. I encourage students to consider what they see themselves doing with the pastel. The underpainting serves as a setup for the application of pigment much like the foundation of a house supports what lies above. When employing an underpainting it’s easy to put in too much, so keep reminding yourself that it’s the setup—the underlying foundation upon which the pastel painting will be built.
There are many different techniques that can be used in the underpainting or setup phase. We each develop our own individual process through experimentation and exploration of various surfaces and products. It’s important to follow good archival practices when experimenting.
The first factor to consider is the surface. Some surfaces won’t accept certain chemicals and some mediums will fill the tooth of the surface, thus impeding the application of pastel. So, before starting your masterpiece, be sure to experiment on a scrap of the surface to make sure it will accept the underpainting and allow for the subsequent application of pastel.
The next major decision is whether to use pastel for the underpainting or to employ another medium. Many artists opt for a mixed-media approach, applying the underpainting in watercolor, gouache, liquid pigments, acrylic or even thin oil paints. If using pastel, harder brands often work best, allowing for the staining of the surface without filling the tooth. Depending on the surface, pastel may be spread dry or diluted with a wet solution such as water, rubbing alcohol or mineral spirits. For most methods that use water, the paper should be pre-mounted or of a heavy enough stock to withstand the swelling and wrinkling that may occur. No matter which method you end up using, remember to keep the underpainting as thin as possible, in order to retain enough tooth for the application of pastel.
That’s just the start of my considerations for an underpainting. In next week’s blog, I’ll talk about my process for selecting color and value for an underpainting.