Aquatint

This is the term used to describe the process of adding tone (not colour) to a line etching. Instead of a surface of wax the metal plate is given a thin layer of resin dust which, when heated, adheres to the metal. The resin protects the metal from acid but allows the acid to attack the metal between the resin grains. This produces a fine network of “valleys” which hold ink. Varying the depth of the valleys will vary the amount of ink held and thus vary the tone value.