Etching on steel is performed by drawing the design with Brunswick black, laid on with a hair pencil. It is then bedded in glazier's putty, or the bordering wax used for etching, and the aquafortis poured over it, and suffer ed to remain till it be bit to the requisite depth. It may then be poured off', and the black cleaned away with a little turpentine.
The method of mezzotinto is performed by first laying a ground on the copper, by roughening the whole surface with a serrated or toothed instrument, and moved in va rious directions, till it be brought to such a state as to be capable, if an impression were taken from it in this stage of the process, of giving a flat black tint to the whole. The outline is then traced with an etching needle. The lightest parts are then scraped to the greatest smooth and the middle tints are also produced in the same manner, by scraping them, so as to leave a greater or less portion of the ground, according to the depth required.
Engraving on stone, is a method of imitating pen and ink drawings, for which the inventor some years ago ob tained a patent. It is performed on a slab of marble, or some close-grained stone. The design and effect is made out, with a pen clipped in a solution of lac, in the ley of pure soda, with a little soap, and coloured with lamp black.
When the drawing has been on the stone for three or four days, or when the ink is perfectly dry, it is soaked in water. In this state it is daubed with printer's ink from the balls, and the ink will adhere to the design and not to the stone. The impression will be taken from it in the same way as the letter-press printing, by putting a sheet of damp paper over it, and subjecting it to the action of the printing-press.
Another method of engraving or printing on stone was invented by Alois Senefelter, a native of Prague in Bohemia, who obtained an exclusive privilege for it front the Elector of Bavaria, in i 801 ; and, in 1803, a like pri vilege from the Emperor of Austria. He accordingly established stone printing-houses at Munich and Vienna; and, under his direction, similar establishments were formed in France and Italy : but it is at Munich that the art has been brought to the greatest perfection. It has been found well adapted for imitation of wood-cuts, draw ings, music, all kinds of writing, and geographical maps.
The method is, to take a calcareous stone or slab of marble, with a good polish, of from two to three inches thick, and of a size proportioned to that of the work to be executed on it. The design, notes, or letters, are marked out with a solution of gum lac and potash, co loured with lamp black. When they are dry, the stone is covered with aquafortis ; and the acid attacking all parts of the stone except those which have been impreg nated with the resinous ink, the drawing remains untouch ed, and appears like the block of a wood cut. When the acid has corroded to a sufficient depth, the slab is wash ed with clean water, and, while wet, printing ink is ap plied to it with balls in the usual way, and put through the rolling press. At each proof, the block must be
washed with water. This method, for expedition, cheap ness, and durability, has greatly the advantage over the usual processes, particularly for music; and it is said, that, at the stone printing office at Vienna, thirty thou sand impressions were taken off the same slab, and the last impressions were nearly as good as the first.
Etching on glass is performed by laying on a ground consisting of a thin coat of bees-wax, and making out the design with an etching needle. It is then covered with sulphuric acid, and sprinkled over with pounded Derbyshire spar (fluor spar). It must be taken off after four or five hours ; and when cleaned with oil of tur pentine, the etching will appear, leaving what had been covered with the wax untouched. By this method, glass vessels are graduated, or ornamented.
This process is sometimes reversed, by putting on the design or ornament with a solution of bees-wax in tur pentine, and exposing the ground to the action of the acid, which, when sufficiently corroded, will leave the orna ment untouched, and the ground deprived of part of its polish and transparency. It is to be observed, that the sulphuric acid does not immediately act on the glass, but only by expelling one of the constituent parts of the spar, (the fluoric acid,) so that the effect o( the corrosion will be according to the quantity of the fluoric acid evolved, acting on the glass ; and as it possesses much greater activity in the gaseous state than when combined with water, the operation will be performed more expeditious ly by exposing the plate to the action of the gas as it evolves, properly secured to prevent its escape ; and its this way, several plates may be bit at once.
Seal-engraving, which is performed both in cameo and. intaglio, was an art much practised by the ancients. it was performed on all sorts of precious stones, but onyx was the most commonly used for this purpose. The operation is performed by inserting the tools into the ax 'is of a small iron wheel, which is attached to an appara tus like a turner's lathe, and kept in motion by' the foot. The tools are tightened by a screw, and the stone to be engraved is applied by the hand to the tool as it revolves, and is shifted and conducted as required. The tools arc generally of iron, and sometimes of brass ; their forms are various, generally resembling chisels and gouges: some have small round heads like buttons, others flat, &c.; and when the stone has been engraved, it is polish ed on wheels of hair brushes and tripoli.
See Strutt's Dictionary of Engravers ; Bryan's Dic tionary of Painters, Engravers, arc.; Landsecr on En graving ; Heineken Icier Generale d'une Collection com plette d'Estamizes ; Vasart l'ite de' Pittori ; (Mandl, Abecedario Fitton° ; Christ. Dictionnaire des Monogram mes ; Papillon Histoire de la Gravure en Bois ; Felibien Principes de l'Architecture et des autres Arts qui en de pendent. (r. G.)