Etching is an engraving process in which acid is used to make a picture or design on a metal plate. The term "etching" is also applied to a print made from an etched plate. Unlike other methods of engraving, etching requires no tools to cut into the plate. Instead, an acid eats the design into the metal.
The metal plate, usually copper, is first carefully polished and cleaned. An etching ground, usually composed of wax, resin, and pitch, is spread on the surface. The design is made by drawing through the wax covering with a pointed metal object or etching needle without scratching or incising the plate itself. Before prints can be made, all the varnish and etching ground must be removed from the plate. Ink is then forced into the grooves, and the rest of the surface is wiped clean. The plate is covered with a moist sheet of paper. As it is run through a printing press, the inked design is transferred to the paper.
Because of the heavy pressure of the machine, only a certain number of clear prints can be made before the etched lines become indistinct. A copperplate produces about 50 prints, but a steel plate makes several hundred. In either case the prints are numbered, and those with lower numbers are of greater value. When the design is completed, the plate is put into an acid solution and the exposed areas eaten away.
The depth of the groove eaten away by the acid determines the kind of line that will appear on the print. For thin, light lines the etcher removes the plate from the solution as soon as the acid has bitten faint grooves. The grooves that are to remain faint are then covered with etching ground or a varnish to protect them from further action by the acid when the plate is returned to the solution. The plate is immersed repeatedly until the desired effect is achieved.
The technique of etching was first used for print-making in about 1500. Jacques Callot introduced important technical refinements in the 17th century. During this period, etching reached its peak as an art with the works of Van Dyck and, especially, Rembrandt. Also outstanding were the later etchings of Piranesi and Goya. In the 20th century, etching continues to be a popular graphic art, and many new techniques have been developed. Modern artists who are known for their etchings include Picasso, Matisse, and Chagall.