Wood engravings are made from the end-grain surface of very hard wood, usually boxwood, as opposed to woodcuts, which are made from side-grain planks of wood neither so hard nor so expensive. Rather than cutting away non-printing areas with a knife, wood engravings are made with fine engraving tools which are used to engrave the non-printing areas with incredible precision and detail.
Drypoint prints are created by scratching a drawing into a metal plate with a needle or other sharp tool. This technique allows the greatest freedom of line, from the most delicate hairline to the heaviest gash. In drypoint, the slightly raised ragged rough edge of the line, known as the burr, is not scraped away from the surface but stays on the surface of the plate to print a velvety cloud of ink until it is worn away by repeating printings. Drypoint plates (particularly the burr on them) wear more quickly than etched or engraved plates, allowing for fewer satisfactory impressions and showing far greater differences from first impression to last.
Etching has been a favorite technique for artists for centuries, largely because the method of inscribing the image is so similar to drawing with a pencil or pen. An etching begins with a metal plate (originally iron but now usually copper) that has been coated with a waxy substance called a “ground.” The artist creates the composition by drawing through the ground with a stylus to expose the metal. The plate is then immersed in an acid bath which “bites” or chemically dissolves the metal in the exposed lines. Before printing, the ground is removed and the plate is inked and then wiped clean. The plate is covered with a sheet of dampened paper and run through the press, which not only transfers the ink but also forces the paper into the lines, resulting in the raised character of the lines on the impression. Etched lines usually have blunt rather than tapering ends.
Aquatint is an etching process concerned with areas of tone rather than line. For this technique, the plate is covered with a ground or resin that is granular rather than solid (as in etching) and bitten, like etching, with acid. The tonal design of the print is produced by protecting certain areas of the plate from the acid with an impervious varnish, by multiple bitings to produce different degrees of darkness, and by the use of multiple resins with different sized grains.
Lithographs are made using an oily or greasy medium such as a crayon or tusche (an oily liquid wash) to draw a composition on a flat, ground stone. The surface of the stone is then flooded with water, which is repelled by the greasy areas. Printer’s ink is applied to the stone with a roller, sticking only to the greasy sections of the composition. The stone is then covered with a sheet of paper and run through the press to create the print.
Source: “Glossary of Printmaking Terms and Techniques,” Lower East Side Printshop, Inc.