Etching, the art of engraving with acid on metal; also the print taken from the metal plate so engraved. In hard-ground etching the plate, usually of copper or zinc, is given a thin coating or ground of acid-resistant resin. This is sometimes smoked so that lines scratched through the resin will be clearly visible. A needle exposes the metal without penetrating it. When the design is completed, the plate is submerged in an acid solution that attacks the exposed lines. During the bath the plate is frequently removed, and such lines as are bitten to sufficient depth are coated with stopping-out varnish. The lines receiving the longest exposure to the acid will be the heaviest and darkest in the print. It is also possible to apply the acid locally to the plate. In printing, all varnish is removed, the plate is warmed, coated with etcher's ink, and then carefully wiped so that the ink remains in the depressions but is largely or wholly removed from the surface. It is then covered with a soft, moist paper and run through an etching press.