ground

…by far the most popular ground.

The ground (i.e., the inert paint layer covering the support below the painting itself) can ordinarily be regarded for conservation purposes as part of the painting layers. Occasionally, the ground may lose its adhesion to either the support or the paint layers, or the ground may…

…with an acid-resistant coating (ground). The design is then scratched or pressed into the ground, exposing the metal in these areas. Finally, the plate is submerged in an acid solution until the desired depth and width in the exposed areas is reached.