Intaglio Printing
A printing process in which the image is incised or etched into a metal plate using a variety of techniques and tools. Ink is applied to the recessed areas of the printing plate by wiping, dabbing, or a combination of both. The paper receives the ink from the incised marks and not from the top surface of the plate, although thin films of ink may be left on the surface to produce a variety of tonal effects. For intaglio printing, the paper is dampened so that under printing pressure it will be squeezed into all the inked recesses of the plate and around it (leaving a PLATE MARK if the plate is smaller than the paper). One of the distinguishing characteristics of this type of printing is that the dried ink impression stands up from the paper in very slight relief, perceptible by touching with the fingers or by close inspection.
In all intaglio prints except mezzotint the design is produced from ink in lines or areas below the surface of the plate. The smooth surface is wiped of ink before printing. Considerable pressure is used in the press to force the ink out of the lines and areas and, to an extent, to force the paper into them, so the final printed image will appear to be slightly raised above the surface of the uninked paper.

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.

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.

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.

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 and second and third bitings are.used to produce variations of darkness.

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.

Relief Printing
A printing process in which the impression is created by the uncarved areas or the unprepared surface of the PRINTING ELEMENT, which has been inked with a ROLLER, BRAYER, or other tool. The cut, or incised, areas do not usually print, since they are recessed and are rarely inked. Nonetheless, during a run paper is often pushed into these sunken areas, creating an embossed effect. The recessed areas do print when the printing element is inked in the same manner as an etching plate, with the surface wiped dean, leaving ink in the recesses. WOODCUT and LINOCUT are usually used for relief printing.

In all relief techniques it is the surface of the block that is inked and printed and, given perfect printing, all lines or surfaces will be equally dark. Moderate pressure in the press will emboss the paper to an extent, so the inked design will lie slightly below the uninked surface of the paper.

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.

Chiaroscuro Woodcut.
The design is divided among several blocks, each to print a different color, with or without overlaps. Those areas cut away in all blocks will not print at all and thus provide highlights of the natural color of the paper used, the light of the "light-dark" technique. The blocks must be carefully matched in placement of the design (registration) and the paper must pass through as many printings as there are blocks.

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.

Linocut or linoleum cut.
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.

Planographic Printing
In planographic printing, as opposed to intaglio and relief processes, there is no difference in level between the inked surface and the non-inked surface.

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.

The design is drawn or painted on the polished, or grained, flat surface of a stone, usually Bavarian limestone, with a greasy crayon or ink. The design is chemically fixed on the stone with a weak solution of acid and gum arabic. In printing, the stone is flooded with water which is absorbed everywhere except where repelled by the greasy ink. Oil-based printer's ink is then rolled on the stone, which is repelled in turn by the watersoaked areas and accepted only by the drawn design. A piece of paper is laid on the stone and it is run through the press with light pressure, the final print showing neither a raised nor embossed quality but lying entirely on the surface of the paper. The design may be divided among several stones, properly registered, to produce, through multiple printings, a lithograph in more than one color. A transfer lithograph (French, autographie) employs the same technique, but the design is drawn on special transfer paper and is later mechanically transferred to the stone. A zincograph is the same technique, but employing a zinc plate rather than a stone.

Cliche-Verre (Glass Print).
A glass plate is covered with ink or paint and a design is drawn through it with a stylus or brush, producing a negative matrix. A piece of photo-sensitized paper is placed beneath it and it is exposed to light. A positive, proto-photographic image appears on the paper. It should be noted that this is a print without printing; there is no ink on the paper.

IMPORTANT NOTE: Techniques are often combined: etching with drypoint, etching with aquaint, engraving with etching, woodcut with wood engraving, even etching with chiaroscuro woodcut. There are, in addition many dozens of other techniques used, usually in combination with these basic ones, and many variations of the basic techniques.