Most of my drawings while working from the figure are from poses that will last about an hour.
I usually work initially with graphite in an 11 x 14 sketchbook and then if I like the pose I will have the model repeat it for another forty minutes to an hour. While working the second session, I will change my medium just to keep things fresh and to prevent boredom. The example above shows my first drawing with graphite and the second larger drawing (18 x 24) which was done, in this case, with charcoal and gray value pastels on toned paper. It amazes me sometimes at how quickly the second drawing comes together. This, I believe, is due to the intense observation as well as the aesthetic decisions and thoughts that come about while working on the first sketch.
