ACQUAFORTE

The matrix is usually a copper or zinc plate, but other metals can also be used. The plate, which has been thoroughly degreased, is completely covered with a bituminous paint that makes it resistant to acids. The design is traced onto the painted plate with a steel point: where the point passes, the paint is removed and the metal is exposed. Obviously, points of different shapes can be used to obtain different types of marks.

Once the design is complete, the plate is immersed in a solution of water and nitric acid (this mixture was formerly known as "etching"). This is the etching stage: depending on how long the plate is immersed, the acid will etch more or less deeply and the mark will be more or less intense when printed. The gradation of the marks can be achieved not only by using different points, but also by successive etching, covering the marks that are to be less engraved each time. Once the etching is complete and the protective varnish has been removed from the matrix, the printing process can begin. For this operation, a calcographic press is used, which consists of two superimposed cylinders separated by a sliding plate: the movement is impressed by rotating star-shaped arms attached to one of the cylinders. The paper, which is made of a special mixture, must be moistened so that, under the pressure of the cylinders, the fibres are more easily pushed to draw the ink into the grooves of the matrix. The plate must be inked for each print run: the ink is spread with a leather pad over the entire matrix, which is kept warm on a stove. Once the plate has cooled, the ink is cleaned off, it is placed on the press bed, damp paper is placed on top, a felt cloth is spread over it and, once the pressure of the cylinders has been adjusted, it is turned to finally obtain a print. Incidentally, it should be noted that printing is not a marginal or mechanical phase, but an integral and decisive part of the entire process leading to the finished sheet. It should also be said that most artists usually entrust the printing of their plates to professional printers, but it is certain that the engraver is always the best printer of his own plates and there is no good engraver who is not also a good printer.