What is grisaille?

grisaille - A style of monochromatic painting in shades of gray, used especially for the representation of relief sculpture, or to simulate one. Achromatic painting. May refer to a gray underpainting, laid for subsequent color glazing. Also, a kind of paint which can be fired onto glass. (pr. greez-eye', or griz-eye') There are several sites Grisaille painting, here are a few: http://www.lindacoulter.com/Grisaille.htm http://newberryworkshop.com/Tutorial/gris/gris.html http://www.coggart.com/grisail.html