AQUATINTA ENGRAVING, a mode of engraving which is an imitation of water colour or India-ink drawings. The inventor, a German artist named Le Prince, was born at Metz in 1723. His method was to sift black resin over a clean copper plate ; the resin was fixed by a moderate heat sufficient to make the dust adhere without fluxing or becoming an even varnish: he thus formed a granulated surface, on the plate, usually called a ground, which suffered very little from the action of the diluted acid, yet allowed it to corrode very freely in the small spaces left between the grains of the resin. Mrs. Ca therine Prestel, also a German, improved much upon the meagre works of Le Prince, and executed several large works with so much success, that little more was found wanting than a ground that would adhere better to the plate and yield a greater number of impressions ; this was effected by dissolving the resin in alcohol, and then pouring the mixture over the plate, the quantity of resin determining the coarseness or fineness of the grain. The modern aquatinters have another advantage over their predecessors in using a composition for painting the forms of leaves of trees, or other objects, where the trouble of surrounding the forms by a varnish would be too great. This composition is made of treacle, whiting, and gum. When used, it must be thoroughly dry before the varnish is passed over it; the varnish also must be allowed time to dry ; after which, cold water poured on the plate will in a few minutes bring off all the composition and the varnish which had passed over it, leaving the forms perfect, and the ground in those places free to receive the acid again. The remainder of the plate is permanently stopped out by a re sinous varnish ; with this also the margin of the plate is to be varnished, leaving a narrow strip of the ground for trials or tests. The design intended to be engraved is then made on the ground; this is done in the following manner :—The design is first copied on very thin transparent paper, called tracing-paper; between this tracing and the prepared ground on the plate a thin sheet of paper is placed, which has been rubbed over with lamp-black or vermillion, and sweet oil; every line of the design is then gone over with an instrument called a blunt point, with amoderate pressure, and is thus transferred to the ground so se curely that the acid cannot destroy it.
Before the acid is poured on the plate, a border or wall of wax (formed of burgundy pitch, bees' wax, and sweet oil), about an inch in depth, is placed round the margin of the plate.
The plate being so far made ready, the completion of the design is resumed by stop ping out the highest lights on the edges of clouds, water, &c., with a varnish of Canada balsam, oxide of bismuth, and turpentine. Next pour on diluted aquafortis ; let it remain, according to its strength, from half a minute to a minute, then pour it off, and wash the plate three or four times with clean water, and dry it with a clean linen cloth or a pair of bellows. If on trying the strip the tint is found not to be sufficient, repeat the acid for another half minute, and then proceed. The colour of the bismuth varnish must be changed for the second stopping out, by adding a little chrome-yellow, vermillion, or lamp-black, or any other colour that is not destroyed by the acid. The colour is to be changed after each application of the acid, that the engraver may remember in what places he has carried for ward his work, what tints have been softened at their edges, &c. The acid should be strengthened a very little after each applica tion. When the ground changes to a gray colour it is beginning to fail, and must be taken off by heating the plate till the bordering wax will lift off; after this, sweet oil is applied to the whole surface, and a brisk heat beneath the plate will bring off all the different var nishes with a linen cloth ; then an oil rubber, made of fine woollen cloth, rolled up hard and the end cut off, applied with sweet oil, will takeout the stains ; tints which are too strong may be softened or even rubbed out, The plate is now cleaned with spirits of turpentine and sent to the printer to prove, after which it is to be exceedingly well cleaned with turpen tine, &c., and another ground laid; this should be done in such a manner as to make the grains fall exactly on the granulations of the former ground, which is called re-biting. It is done by making the ground much stronger than the one used before. The process for the second ground is the same as for the first; retouching with the acid those tints which re quire more depth, and stopping out those parts that are sufficiently dark. Another proof must be taken, and the plate then finished with the burnisher, which some use with oil, but others prefer to use dry, previously filling the whole plate with powdered white lead, by which it can be seen how much has been bur nished down according to the quantity of co lour left in the plate.