THE TECHNIQUE
First of all, the techniques of artistic reproduction by printing take their name from the material of which the matrix is traditionally made, followed the suffix - grapby (from the Greek grapbo, to write, to draw). In order of historical appearance, we have:
Xylography: relief engraving on wooden(from the Greek Ksylon) matrices.
Serigraphy: technique that uses a cloth matrix, traditionallysilk (from the Latin saeta or sate ).
Calcography: hollow engraving traditionally on copper(from the Greek kbalkos) matrices. So the name deries from this Greek term, and not, as some think, from the Latin calcare, from calx, calkis, heel, referred to the impression left by the matrix in the printing process.
Litography: flat printing traditionally on stone(from the Greek litbos) matrices. The stone is calcium carbonate, this time not from the Latin calx, calcis but from the Greek kbaliks, pebble. Calcographical techniques Calcographical techniques are divided in two categories, depending if a mordant is used or not: indirect are the techniques in which the carvings are obtained using a mordant, while direct are those in which the signs are produced mechanically, directly.
Etching
The more evocative Italian term, acquaforte, derives from the medieval name of nitric acid, aqua fortis, strong water. It is an indirect technique the most used by engravers, who in fact, in English, are normally called etchers. It is based on the chemical removal of metal from the matrix, using a corrosive liquid called mordant . Historically, the great merit of etching was to free the creativity of artists from the burin and from the need either of a long apprenticeship or of artisans who knew how to use the burin. The plate is first smoothed, cleaned and degreased, then varnished with a special acid-resistant varnish, essentially made of wax and tar. On the surface, after such preparation, the drawing is made with a point that removes the varnish and uncovers the underlying metal, which must be corroded by the acid. Points may have different sizes and shapes to obtain lines of different width, thus widening a little the range of possibilities (flat, truncated, cat’s tongue points);the author however, draws almost as if were using a pen on paper. The biting process, the corrosion by the acid, follows. Innumerable “recipes” for mordants exist, depending on the metal used and the tastes and the experience of the etcher. The most common, can act on many metals. The sign is less clear than the one obtained with the burin, but it can withstand large editions. Its modulation, width and depth depend a little on the points used and much on the biting process. The international abbreviation for this technique is C3.
Aquatint
It is relatively recent technique, allegedly invented by the French etcher Jean Baptiste Le Prince in 1768. In aquatint, the sign as expressed in etching, burin and drypoint is bypassed: the images are obtained by filled areas, zones of different tonal intensity, more or less defined or with contours. The principle is the same as the cross-hatching of news-papers and magazines: the ink is mono-tonal and, in order to obtain all shades of the color - normally black, the image is decomposed in miniscule points that the eye does not perceive; the ratio between white and the colored points determines the shade. In this technique, the author creates a sort of hand made crosshatching called graining. The methods used are many, almost all indirect, that is with a biting process. In the classic one, a powder of resins, typically colophony, or tar is nebulized in side a box which contains the plate. The plate, on which the powder has settled, is then heated to a high temperature to meld the resin and make it stick to the plate. There will be tiny points covered and tiny points uncovered: after the biting process they will respectively correspond to the whites and to the blacks. Zones which must not undergo aquatint, to remain white, or those that have reached the desired shade, are covered by the varnish so that they do not enter in contact with the mordant. With experience and skill in graining and in using the biting process, it is possible to obtain any shade. The international abbreviation for this technique is C5
Mezzotint
Mezzotint is another direct technique, though an indirect variation, when a mordant is used to prepare the plate , exists. In the classical version, the matrix is grained with a strong dented half moon-shaped steel blade called rocker or berceau (fromthe French for cradle). By rocking this tool and pressing innumerable times its teeth on the matrix, the surface is etched with thick barbs that make the print of an intense and velvety black. The tool is moved on the matrix with a rocking motion and a moderate and constant pressure. A “correct” path exists: first the plate is crossed vertically, then horizontally, then diagonally at 45 degrees from right to left, then diagonally from left to right. The four series make up a round, and to prepare the metal adequately, from 10 to 15 rounds are required. Starting from black, by flattening and scraping the barbs generated by the rocker, passing by lighter and lighter tones the purest white can be obtained. This technique allows very soft and pictorial graphic results, with a great tonal variety. Mezzotint too, a relative of drypoint, has a low resistance to printing, so than copper plates are normally used. The international abbreviation for this technique is C7.