Etching [German: "ätzen"; Dutch: "etzen"] is a process of relief printmaking developed in the 16th century. Traditionally regarded as the noblest technique in the graphic arts, the process of etching is also known as "biting". A drawing is bitten, that is, a mordant or acid is used as an etching agent to inscribe the metal plate. Relief-printing etching techniques include not just mordant etching but also aquatint, soft-ground etching (the crayon manner: incorporating chalk features), stipple etching, vernis mou (another form of soft-ground etching: the plate is coated with an etching ground that is at least half tallow, therefore greasy) and color etching. A special form of etching is drypoint etching, which operates without acids, that is, the lines are merely drawn under the exertion of great pressure by the drypoint needle, resulting in delicate, light prints. In mordant etching, the etching plate is coated with an acid-resistant etching ground. This acid-resistant etching ground or resist consists in a mixture of wax, mastix and asphalt (bitumen). After application of the resist, the drawing is lightly incised with needle (steel-etching needle) or a roulette in the resist down to the bare copper or steel of the plate. The plate is now immersed in an acid bath (the acids most common used for this purpose are nitric acid and hydrochloric acid; also Dutch mordant, which is a solution of potassium chlorate and hydrochloric acid), in which the exposed metal is etched. The longer the plate is left in the acid, the deeper the lines etched in the metal so that they later produce a more intense and darker print. If desired that only some parts of the drawing should stand out more vividly in the print, the other bare places on the plate are stopped out with special varnish to protect the parts that are not to be bitten again and the plate is once again immersed in the acid bath. A single plate can, therefore, be bitten several times to attain subtle gradations from the palest grey to velvety black. After the etching ground has been removed, the plate is subjected to the same procedure used in other relief-printing processes - such as copperplate engraving - and inked with a dabber. The ink can be rubbed (wiped) so that ink is only left in the most deeply incised lines for printing. Under the application of pressure from the press, the ink on the plate leaves its imprint on moistened proof paper. The technique of etching developed out of copperplate engraving in the 16th century. The mordant process itself came from engraving on silver and armour. Albrecht Dürer (1471-1528), a goldsmith's son, served an apprenticeship as a goldsmith under his father. It was Dürer who perfected the copperplate engraving by experimenting with etching techniques (on copper plates) and drypoint. He produced his first copperplate etchings around 1515 (The Agony in the Garden: Christ on the Mount of Olives; Landscape with Canon: 1518). Etching and drypoint matured in the hands of Rembrandt van Rijn. Rembrandt also skilfully exploited repeated used plates to produce prints in different states. Towards the mid-19th century etching and copperplate engraving finally lost their primacy as the most important printing and reproducing techniques when lithography (then also known as zincography when a zinc plate was used) and zinc-plate photoengraving were invented, both of which made it possible to print much larger editions.