ILLUSTRATIONS OF UNDERPAINTING AND OVERPAINTING. Underpainting has interested me because the whole idea of painting in layers is novel for me. The wikipedia article on underpainting links to two articles with illustrations which show how painting in layers works. This post by Hanneke van Oosterhout on the Art and Perception blog begins with the observation that rather than use a neutral monochromatic underpainting, artists like Jan van Eyck used layers of bright color for underpainting. She shows how she paints a bunch of grapes with the first layer of underpainting being bright and the layers that follow having more realistic and darker colors. The process affects the way we see: “the brightness of the underpainting color shows through and gives life to the colors.”
This post by Karl Zipser on his blog shows the process, including a section that is overpainted and a section that is underpainted. He says that an important theme in layered painting is: “make something strong contrast, then paint over it to make more subtle contrast.” Zipser’s explanation of the process is very detailed and informative.