While engraving evolved from the craft of goldsmithing, etching, in which the work of cutting into the metal is accomplished through the action of acid, is closely related to the armorer’s trade. A plate of metal is first covered with a layer of acid-resistant varnish or wax, called the "ground." The artist then scratches through the ground with an etching needle to expose the metal beneath. When the design is complete, the plate is dipped in acid, which eats away the lines where the metal has been exposed. The depth of the lines depends on the length of time the plate is exposed to the acid. Once the ground has been removed, the metal plate, with its incised lines, can be printed in the same way as any intaglio plate. While the printing requires considerable craft, the incising of the coated plate with the etching needle can be done by anyone who knows how to draw, encouraging many painters to try their hand.