ENGRAVING, the art of cutting or incising designs on metal plates or blocks of wood, for the purpose of print ing impressions from them with ink on paper, or other similar substance. Works of this sort belong to two classes: en gravings on metal, in which the lines to be printed are sunk or incised, and en gravings on wood, in which the lines to be printed appear in relief, the wood be tween them being cut away. In the for mer, the plate having been inked and wiped on the surface, retains the ink only in its hollowed lines, from which it is conveyed to the paper by the pres sure of the printing press; in the latter, only the elevated portion of the surface of the block is inked by means of a roller, and, being subjected to the press, it prints as a raised type.
Engraving on Metal.—The metal most commonly used for engraving has been copper; but during the 19th century steel was largely employed on account of its hardness. Steel is less readily en graved than copper, and yields a less free and artistic result; but as the sur faces of copper plates can now be pro tected by an extremely thin coating of steel deposited by galvanic action, which can be renewed as often as is necessary, they are enabled to yield a large number of excellent impressions without being worn. Zinc plates have also been em ployed to some extent for etchings. The earliest of the impressions taken from engraved plates are those most valued by connoisseurs, on account of their sharpness, clearness, and richness, quali ties which are gradually lost as the surface of the metal becomes worn by repeated printing. The term "work ing proofs" indicates trial impressions printed by engravers for their own use, to test the state of their work during its progress. "Artist's proofs" are those bearing the signature of the painter or engraver, or both. "Proofs before let ters" are those thrown off before the printed titling, etc., has been added; and "open letter proofs" are those in which the letters of the title have been added merely in outline.
Line Engraving.—The practice of line engraving originated with the early Italian goldsmiths, who in this manner were accustomed to take proofs of the metal objects which they decorated with engraved designs, in order to test the progress of their work; and these nielli, or highly decorated plates of metal, in which the incised lines or patterns were to be filled black composition, are regarded as the earliest engravings. A pax or metal plate used in the Roman ritual to receive the kiss of peace, ex ecuted by Maso FiniguerTa, in 1452, for the Church of San Giovanni in Florence, is considered to have been the first metal from which impressions on paper are known to have been taken.
Etching.—In this process a polished metal plate is coated with a thin trans parent surface or "ground," impervious to acid. A mixture of white wax, gum mastic and asphaltum made into the form of a ball and covered with silk is applied to the heated surface of the plate, and melting exudes through the cloth, when it is spread evenly over the metal by means of a pad of cotton-wool covered with silk, termed a "dabber." The plate is then exposed to the smoke of wax tapers till it becomes of a uni form which enables the etched line, disclosing the shining metal, to be visible on its surface. On this plate, so prepared, the design is drawn with an "etching needle," a sharp steel point fitted in a handle, and held like a pencil in the artist's hand. This needle dis closes lines of the bare metal ready to be eaten or etched by the acid. The back of the plate having been protected by an application of Brunswick black, it is placed in the "acid bath," a flat tray filled with a mordant, usually composed of nitric acid diluted with an equal vol ume of water, which attacks and cor rodes the metal in the lines that have been exposed to its action by the needle. After sufficient time has been allowed for the palest lines of the subject to be bitten, the plate is removed from the bath; these lines are covered with a "stopping-out varnish" of Brunswick black, applied with a brush, which pro tects them from further action of the acid; and the plate is returned to the bath, which attacks the lines still ex posed. This process is repeated as often as necessary to produce the desired variety in depth of the various lines of the design. When the biting is completed, the plate is finally removed from the bath, the "ground" is cleaned off with turpentine, and the design appears in cised on the metal. The plate is then inked and printed. Various methods of etching, and modifications of the process described have been introduced. Sey mour Haden and James MeN. Whistler stand at the head of the painter-etchers in England. Alphonse Legros and Hu bert Herkomer have also done much to stimulate interest in the art. Among the younger painter-etchers are William Strang, Frank Short, and R. W. Mac beth. Among the mc— talented of mod ern etchers in America may be named Frank Duveneck, Otto Bacher, Henry Farrer, Joseph Pennell, Stephen Parrish, Mary Nimino Moran, Thomas Moran, Swain Gifford, and Charles A. Platt.