Source for definitions:- Tate Glossary of terms
Etching
An intaglio technique which uses chemical action to produce incised lines in a metal printing plate.The plate, traditionally copper but now usually zinc, is prepared with an acid-resistant ground. Lines are drawn through the ground, exposing the metal. The plate is then immersed in acid and the exposed metal is 'bitten', producing incised lines.Stronger acid and longer exposure produce more deeply bitten lines. The resist is removed and ink applied to the sunken lines, but wiped from the surface. The plate is then placed against paper and passed through an intagio press with great pressure to transfer the ink from the recessed lines. Sometimes ink may be left on the plate surface to provide a background tone. Etching was used for decorating metal from the 14th century, but was not probably used for printmaking much before the early 16th century. Since then many etching techniques have been developed, which are often used in conjunction with one another: soft-ground etching uses a non-drying resist or ground, to produce softer lines; spite bite involves painting or splashing acid onto the plate; open bite in which areas of the plate are exposed to acid with no resist; photo-etching is produced by coating the printing plate with a light-sensitive acid-resist ground and then exposing this to light to reproduce a photographic image. Foul biting results from accidental or unintentional erosion of the acid resist.
Gouache
A term used in France in the 18th century to describe a type of paint made from pigments bound in water-soluble gum, like watercolour, but with the addition of a white pigment in order to make it opaque. Larger percentages of binder are used than with watercolour, and various amounts of inert pigments such as chalk are added to enhance the opacity. Gouache forms a thicker layer of paint on the paper surface and does not allow the paper to show through.It is often used to create highlights in watercolours. Today the term 'gouache' is often used loosely to describe any drawing made in body colour. Body colour is any type of opaque water-soluble pigment; used by artists from the late 15th century. Lead white was used until the introduction of zinc oxide, known as Chinese White, in the 19th century.
Linocut
A relief print produced in a manner similar to woodcut. The lino block consists of a thin layer of linoleum (a canvas backing mounted with a preparation of solidified linseed oil) usually mounted on wood. The soft linoleum can be cut away more easily than a wood-block and in any direction (no grain) to produce a raised surface that can be inked and printed. Its slightly textured surface accepts ink evenly. Linoleum was invented in the 19th century as a floor covering; it became popular with artists and amateurs for printmaking in the 20th century.
Lithography
A printing process based on the antipathy of grease and water. The image is applied to a grained surface (traditionally stone but now usually aluminium) using a greasy medium: greasy ink (tusche), crayon, pencils, lacquer or synthetic materials. Photochemical or transfer processes can be used. A solution of gum arabic and nitric acid is then applied over the surface, producing water-receptive non-printing areas and grease-receptive image areas. The printing surface is kept wet, so that a roller charged with oil-based ink can be rolled over the surface, and ink will only stick to the grease- receptive image area. Paper is then placed against the surface and the plate is run through a press. Lithography was invented in the 18th century, initially using Bavarian limestone as the printing surface. Its invention made it possible to print a much wider range of marks and areas of tone than possible with earlier printmaking techniques. It also made colour printing easier: areas of different colours can be applied to separate stones and overprinted onto the same sheet. Offset lithography involves printing the image onto an intermediate surface before the final sheet. The image is reversed twice, and appears on the final sheet the same way round as on the stone or plate.
Monoprint
A unique varient of a conventional print. An impression is printed from a reprintable block, such as an etched plate of woodblock, but in such a way that only one of its kind exists, for example by incorporating unique hand-colouring or collage. The term can also refer to etchings which are inked and wiped in an expressive, not precisely repeatable manner; to prints made from a variety of printing elements that change from one impression to the next; or to prints that are painted or otherwise reworked by hand either before or after printing.
Relief
A relief is a wall mounted sculpture in which the three dimensional elements are raised from a flat base. Any three dimensional element attached to a basically flat wall mounted work of art is said to be in relief or a relief element.
Screenprint
A variety of stencil printing, using a screen made from fabric (silk or synthetic) stretched tightly over a frame. The non-printing areas on the fabric are blocked out by a stencil which can be created by painting on glue or lacquer, by applying adhesive film or paper, or painting a light-sensitive resist onto the screen which is then developed as a photograph (photo-screenprint). Ink or paint is forced through the open fabric with a rubber blade known as a squeegee, onto the paper. Screenprinting has been used commercially since the 1920s and by artists since the 1950s. When it was taken up by artists in 1930s America the term 'serigraph' was used to denote an artist's print, as opposed to commercial work. The term 'silkscreen' (silk was originally used for the mesh) was and still is used, particularly in America.
Woodcut
A method of relief printing from a block of wood cut along the grain. The block is carved so that an image stands out in relief. The relief image is then inked and paper placed against its surface and run through a press. It is possible to make a woodcut without a press (Japanese Ukiyo-e prints for example) by placing the inked block against a sheet of paper and applying pressure by hand. Woodblock printing was used in Europe from the 12th Century, at first for printing textiles, though images were printed on paper by the late 14th Century.