A

Aquatint

A technique of acid-biting areas of tone rather than lines. A ground is used that is not completely impervious to acid, and a pebbly or granular texture (broad or fine) is produced on the metal plate. Stop-out, second and third bites are. used to produce variations of darkness.

B

Bromide

A photographic print created on bromide paper.

C

Collotype

Initially called albertype, after its principal inventor, this process consists in pouring a layer of gelatine mixed with potassium chromate over the surface of a zinc or glass plate which is then exposed to light to receive the image. The gelatine hardens in proportion to the amount of light received, the unexposed parts remaining soft and capable of retaining moisture, and the printing can therefore be done, lithographically: the plate is dampened with water and the ink is applied with a roller. It adheres to the surface in inverse proportion to the amount of moisture retained, the hard areas of gelatine printing the darkest. The reticulated grain of collotype is particularly good for reproducing watercolor, for which the process was much used during the latter part of the nineteenth century.

D

Drypoint

Lines are scratched into the metal plate using any sharp instrument with the same freedom as a pencil. The effect is spontaneous, not formal. Cutting into the plate throws up, on each side of the cut, ridges of displaced metal, which are called burr. In the printing of the plate, these ridges will also take some ink and print a kind of inky glow around the line.

E

Engraving

Lines are incised on a highly polished metal plate by means of a sharp-pointed instrument, diamond-shaped in cross section, called a burin or graver. The tool works like a plough cutting a furrow. The strength of the line may be increased by cutting deeper. The burin is held in a fixed position and, to produce a curved line, the plate itself is turned. This makes engraving a slow and painstaking technique producing controlled, formal results.

Etching

Lines are bitten into the metal plate through the use of acid. To begin with, the plate is covered with a thin, acid-impervious coating called a ground which is smoked to a uniform black. Lines are drawn through the ground with a stylus baring the metal of the plate. Acid is then applied which eats into the exposed areas. The longer the plate is exposed to the acid, the deeper the bite and therefore the stronger the line. Different depths are achieved by covering some lines with acid-impervious varnish (stop-out) and biting others a second (or third) time. The appearance of etchings is usually free and spontaneous but the technique has occasionally been used to produce results almost as formal as engraving.

L

Linocut

An abbreviation of linoleum cut. The technique is a derivation of the woodcut but owing to the supple, relatively soft properties of the material, linocuts have different characteristics. The material takes all types of lines, but is most suited to large designs with contrasting dark and light flat tints. The material is cut with small pen-like tools which have a mushroom-shaped handle. The tools have a variety of forms: straight and rounded edge, double-pointed, as a chisel or a V-shaped chisel, etc. As on a woodcut, the relief parts of the block are inked. For printing a large number of important proofs, the linoleum is attached to a wooden block. Color printing is done with several linoleum blocks. Long disparaged by serious artists as not challenging enough, the linocut came into its own after artists like Picasso and Matisse began to work in that technique.

Lithograph

A printing process in which the image to be printed is rendered on a flat surface, as on sheet zinc or aluminum, and treated to retain ink while the non image areas are treated to repel ink.

M

Mezzotint

The only intaglio technique that proceeds from dark to light rather than the opposite. The metal plate is totally abraded with an instrument called a rocker. Were it inked and printed at this point, it would produce an even, rich black. The design, in areas of tone rather than lines, is produced entirely by smoothing areas of the plate with a scraper or a burnishing tool. The more scraping and burnishing done, the lighter the area.

Monoprint

A unique print produced in such a way that part of the process cannot reproduced (e.g. it may contain an element of monotype)

Monotype

A design is drawn in ink or paint on any smooth surface. While the ink or paint is still wet, a piece of paper is laid on top of it and pressure applied, either with a press or by hand. The process, by its name, is meant to produce a single impression, but there is sometimes enough damp ink left on the plate surface to make a second, weaker, impression.

P

Photogravure

Sometimes known as heliogravure (particularly hand photogravure), this technique is one of the most important methods of industrial printing (the others being letterpress and offset lithography). It is an intaglio process which can be divided into two procedures: (1) Hand photogravure, a derivation of the aquatint in its method of obtaining tone. After sensitizing a copper plate and exposing it to light to form the image, resin or bitumen grain was scattered over it. The procedure continued as for a normal aquatint plate. This technique subsequently developed into a totally photomechanical process: (2) Machine photogravure, in which the tone is supplied by a cross-line screen. It was discovered that the plate could be bent into the form of a cylinder, a development which allowed very fast printing speeds (rotogravure). The technique is used more for magazines and catalogues than for print-making itself.

S

Screenprinting

The principle of screenprinting, or silkscreening, consists in applying stencils to a screen (constructed of silk or of some synthetic or metallic material), in such a way that when ink is applied it is prevented from passing through some parts while penetrating the rest of the screen, thereby printing an image on paper placed underneath. The screen is stretched across a frame and attached to a base in such a manner that it can readily move up and down, so that paper can be easily placed and removed as required. For each impression, the paper is placed against registration tabs to ensure that the printing is done in the correct position. The ink is poured over the masking at one end of the screen and when this has been lowered into position, the ink is scraped across the screen with the aid of a squeegee.

The most important part of the process is the preparation of the screen. Stencils may be applied in a variety of ways, including the use of filling-in liquid, varnish or plastic film. A drawing can be made directly on the surface with a special ink which is removed in readiness for printing after the rest of the screen has been blocked out. A photographic stencil is made by initially sensitizing the screen.

W

Wood Engraving

Tools similar to metal engraving are used on polished blocks of end-grain wood (usually boxwood), but instead of producing lines that will print, they are used to produce non-printing lines. It is the uncut surface that will take the ink and print.

Woodcut

The design is drawn on a wood plank (side grain) and those areas that are not to print are cut away well below the surface with a knife or gouge. Linocut is the same technique using linoleum rather than wood