Grisaille ...

 

Grisaille, painting technique by which an image is executed entirely in shades of gray and usually severely modeled to create the illusion of sculpture, especially relief. This aspect of grisaille was used particularly by the 15th-century Flemish painters (as in the outer wings of the van Eycks’ Ghent Altarpiece) and in the late 18th century to imitate classical sculpture in wall and ceiling decoration. Among glass painters, grisaille is the name of a gray, vitreous pigment used in the art of colouring glass for stained glass. In French, grisaille has also come to mean any painting technique in which translucent oil colours are laid over a monotone underpainting.