AQUATINTA, a method of engraving by aquafortis, the impressions from which very much resemble draw ings in Indian ink. It is effected by covering the plate, (after the intended figure is outlined, by etching, or otherwise,) with a ground, composed of resin, Burgundy pitch, or mastic, dissolved in rectified spirit of wine, which, being poured all over the plate, by holding it in an inclined position, the spirit of wine almost immediate ly evaporates, and leaves the resinous substance in a granulated state, equally disposed all over the plate. A regular grain is thus produced, which prevents the aquaforeis from acting where the particles adhere, and allows it to operate in the interstices only.
The margin, and those parts of the plate which are intended to be white, are pencilled up with a varnish composed of common etching ground (see ETCHING) dissolved in turpentine ; when this is sufficiently dry, border or dike, composed of shoemaker's resin, tallow, and bees-wax, is raised round the plate, to confine the aquafortis ; which, after being properly diluted with water, is then poured on. While it is acting, it must be constantly swept with a feather, to prevent it from biting foul: when it has remained on the plate suffi ciently long to produce the lightest tint required, it is poured off, and the plate washed with water. After it is perfectly dry, those lighter tints are pencilled up as before, and the aquafortis again applied, and repeated till all the different tints are produced which are requir ed ; the wax is then removed, and the varnish and aqua tinta ground taken off with turpentine. A proof of the plate is next to be taken, to ascertain the colour of the different tints ; those that arc too light, must be made darker by rebiting (see ETCHING) or repeating the operation ; and those that are too dark, must be made lighter when you come to finish the plate, by burnishing, scraping, or polishing down with charcoal and oil, which is the preferable method. After all the different tints are obtained as near the colour required as possible, a great deal of trouble and judgment is required in finishing. The leaves of trees, and other minute ob jects, are produced by laying on another ground, and by pencilling them in the same manner as in drawing upon paper, with gun-powder, mixed to a proper consistency with strong aquafortis ; what is required to be darkest must be done first, the aquafortis acting on the copper, while you are pencilling up the lighter parts. Another method of producing a similar effect, is accomplished by mixing fine whiting with a little treacle or sugar, diluted with water, so as to work freely ; and pencilled on the aquatinta ground, the same as on the drawing.
When it is perfectly dry, the whole surface of the plate is laid over with the varnish ; and this part of the opera tion must be performed with a broad varnish-brush, in order that the varnish may be laid on equally and thinly. This coat being perfectly dry, the aquafortis is poured on ; the varnish, where the mixture of treacle was ap plied, will immediately float on the surface of the aqua fortis, and expose those parts to the action of the acid, while the rest of the plate remains untouched, producing thereby an effect similar to touches in Indian ink; the plate is again to be cleaned, and another impression ta ken, to prevent any deception in the shade of the tints: The plate is then finished with the graver, mezzotinto tool, or dry needle.
Another method used formerly to be employed ; but tieing more uncertain and imperfect, is now laid aside : It was produced by covering the copper with pounce or other powder, which, after being heated, adhered to the plate, and resisted the action of the aquafortis.
Great care must be used to procure spirit of wine well rectified, and of the best quality, for the resinous solution, as that of the shops generally contains camphor, which would have the worst possible effect on the grain. The resinous substances commonly employed are resin, Burgundy pitch, and gum mastic, and these are used separately, or mixed in various proportions, according to the judgment of the artist, and the nature of the grain required. A coarse or a fine grain is obtained by using a greater or a smaller quantity of resin ; and the due proportions may be determined by previously apply ing the mixtures to small plates of copper provided for that purpose, till a proper solution is procured. The solution being made, it must be placed for a day or two in asituation .where it will be free from all disturbance, in order that the impurities of the resin may subside, and the fluid become perfectly transparent. This seems to be a better method of freeing it from those impurities than by filtration. The plate itself must be prepared for the grain with the utmost care, by cleaning it well before-hand with rot-stone and oil, and afterwards with dry rot-stone, in order to remove every stain from its surface, and give it a smooth polish. When the com position has been poured on it, great care must be taken to protect it from dust and other light substances float ing in the air; as these, whenever they fall Oil the plate, impede the progress of the solution, and cause light white spots, which can only be removed by laying on a fresh ground.