Underpainting

Here is an underpainting for an oil portrait of a sculptor that I am currently working on.  My reference is a black and white photo ca. 1900.  I always do an underpainting as the first step to any oil painting.

Underpainting for Sculptor by Jaime Cooper

It greatly helps me to:
1.  draw the image (I don't do any drawing in pencil first)
2.  decide on major structural and compositional questions
3.  map out the value structure, especially placement of core shadows

I usually do them in either raw or burnt umber thinned to an ink consistency with turpenoid (and a little stand oil).  Sometimes with a landscape or still life I will use burnt sienna.  Every once in awhile I will go crazy and try something like purple or green.  This can be an interesting take on flesh tones for a portrait.  I use a brush, rag, or Q-tip to wipe out highlights.  After the underpainting is finished I will start painting the color layers over it.