ground

ground. The surface or support on which a painting or drawing is executed, typically paper for watercolours, for example, and canvas for oils; or, more specifically, a preparatory coating applied to such a surface before the picture is begun. The purpose of the ground in the second, more technical, sense is to isolate the paint from the support so as to prevent chemical interaction, to render the support less absorbent, to provide a satisfactory surface for painting or drawing on, and to heighten the brilliance of the colours. Gesso is the ground that occurs most often in the literature of art history. In etching the ground is the acid-resisting mixture that is spread over the plate before work is begun.