The art of producing figures or designs upon metals, stone, wood, and various other substances, by means of lines cut upon the surface. In this extensive sense of the term, the art is doubtless of very great antiquity, repeated mention being made in Scripture of seals, signets, and other works of the graver; but the word usually signifies the art of producing designs as above for the purpose of being subsequently printed upon paper, which copies are also called engravings; and in this sense of the term the art does not appear to have been known or practised in Europe until the middle of the fifteenth century. In the present day it is held in very great esteem, and is very extensively practised. It may be divided into two branches, according to the substances upon which the design is engraved, which is generally either metal or wood, although glass and other substances have been occasionally employed. Of the metals, copper has, until within these few years, been almost exclusively chosen for engraving, on account of its ductility, evenness of texture, and the softness and delicacy of the tints which may be produced upon it; but latterly, steel plates have been very extensively employed for this purpose, and although the engravings thus produced are perhaps somewhat inferior in softness to those obtained from copper, a very high pitch of excellence has been attained, and in point of durability the copper-plates will bear no comparison with steel-plates.
Engraving on copper is performed in various styles, the principal of which are, line engraving, mezzotinto, etching, and aquatinta. Line Engraving is considered as the highest department of the art, and is always employed in the illustration of historical subjects. In this style of engraving the lines are all cut upon the copper by means of an instrument called a graver, the roughness being removed by a triangular steel instrument called a scraper. To trace the design upon the plate (which for every style of engraving should be of the best copper well planished and burnished), it is usual to heat the plate sufficiently to melt white wax, with which it must be covered equally with a thin film, and then suffered to cool; the drawing is copied in outline with a black lead pencil on paper, which is then laid with the pencilled side upon the wax, and the back rubbed gently with a burnisher, which will transfer the lead to the wax. The design is then traced with an etching needle through the wax on the copper, when on wiping it clean it will exhibit all the outlines ready for the engraver.
Mezzotinto Engraving differs entirely from the manner above described, and is chiefly employed for portraits and imitations of Indian ink drawings. The mode of proceeding is as follows: - the plate is prepared by scratching it equally in every direction with a tool called a grounding tool, so as to remove entirely the polish from the surface, which is thus converted into a chaos of intersections, which, if covered with ink and printed, would present a perfectly black impression upon the paper. To transfer the design to be scraped, it is usual to rub the rough side of the plate with a rag dipped into the scrapings of black chalk, or to smoke it with a burning wax taper, as in the process of etching. The back of the design is then covered with a mixture of powdered red chalk and flake white, and laid on the plate, and the outline of the design "being lightly traced with a blunt point, the red particles at the back are thus transferred to the black ground of the plate in the form of a corresponding outline; the process must then be carried on with a scraper, by restoring the plate in the perfectly light parts of the intended print to a smooth surface, from which the gradations are preserved by scraping off more or less of the rough ground, but the burnisher is necessary to polish the extreme edges of drapery, etc, when the free touch of the brush in painting represents a brilliant spot of light.
The deepest shades are sometimes etched and corroded by aquafortis, and so blended with the mezzotinto ground added afterwards, that there is nothing offensive to the eye in the combination. Many proofs are required to ascertain whether the scraping approaches the desired effect, which is done by touching the deficient parts with white or black chalk on one of the proofs, and then endeavouring to make the plate similar by further scraping, or by relaying the ground with a small tool made for this particular purpose, where too much of the roughness has been effaced.
A third method of engraving consists in corroding the various lines by means of aquafortis, the remaining parts of the plate being defended from the action of the acid by being covered with a thin stratum of a composition which resists its effects. This method is termed etching, and is employed both for preparing the outline in other styles of engraving, and also for fining in and completing a picture; and the prints so produced resemble pen and ink drawings. This style is distinguished for the inimitable spirit and freedom of which it admits. The first stage of the process is the preparation of the plate, by covering it with a thin even film of the composition or ground, as it is termed, which is to protect it from the acid. This ground is a combination of asphaltum, gum mastich, and virgin wax, melted over a fire in an iron pot. A piece of this ground is tied on a piece of lustring for use, and another piece of silk is made into a dabber by tying a quantity of cotton wool in it. The copper-plate, secured at one corner by a hand vice, is to be held over a charcoal fire, and the silk containing the ground rubbed over until every part is covered by the melted composition; and before it cools, the silk dabber is applied in all directions, until the surface of the plate is thinly and equally varnished.
When this is completed, several lengths of wax taper twisted together are to be lighted, and the plate being held in the left hand by the vice, the right holding the wax taper, is to be waved gently to and fro under the ground, carefully avoiding touching it with the wick, yet causing the flame to spread smoothly over the surface, which will render it perfectly black, smooth, and shining in a short time. The next object is to transfer the design to the ground, which may be done either by making a tracing with a black lead pencil, or with vermilion, upon thin paper, and applying it carefully to the plate, pass the plate through a rolling-press; or the back of the design may be rubbed with red chalk and fastened to the plate at the corners, and the outline then gone carefully over with a blunt tracer. The outline thus prepared is then gone over with an etching needle, which cut3 through the ground; but particular care must be taken that the point of the needle, though taper, be rounded, so as to avoid the possibility of its tearing the surface of the copper, which would prevent the progress of the point, and ruin the plate when bitten.