gesso

This term refers to a specific preparatory ground used in traditional painting and sculpture. It creates a non-porous, smooth surface that prevents the paint from soaking into the substrate, which would otherwise dull the colors and compromise the adhesion of the pigment. As a noun, it is typically treated as an uncountable mass noun because it refers to the substance itself. When artists refer to multiple applications, they use partitive phrases such as layers of gesso rather than pluralizing the word.