Lithos - Etchings - Engravings
Exhibition of 18th & 19th Century Prints
at Tejas Gallery, Kolkata
from 13th August to 25th August 2012.

Lithography (from Greek lithos, 'stone' and graphein, 'to write') is a method for printing using a stone or metal plate with a completely smooth surface. Invented in 1796 by German author and actor Alois Senefelder as a cheap method of publishing theatrical works, lithography can be used to print text or artwork onto paper or other suitable material. Lithography originally used an image drawn (etched) into a coating of wax applied to a plate of lithographic stone as the medium to transfer ink to a blank paper sheet, and so produce a printed page. The image can be printed directly from the stone plate (reverse orientation), or it can be offset, by transferring the image onto a flexible sheet for printing and publication.

Etching is the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal. As an intaglio method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains in wide use today. In pure etching, a metal plate is covered with a wax which is resistant to acid. The artist then scratches off the ground with a pointed etching needle, creating a picture by exposing the bare metal. The plate is then dipped in a bath of acid, (the mordant) which "bites" into the exposed metal leaving behind lines sunk into the plate. The wax is then cleaned off, and the plate inked and wiped, leaving only the ink in the etched lines. The plate is then put through a high-pressure printing-press together with a sheet of moistened paper, making a print. The process can be repeated many times to make impressions or copies, before the plate shows much sign of wear.

Engraving is the practice of incising a design on to a hard, usually flat surface, by cutting grooves into it. The result may be a decorated object in itself, as when silver, gold, steel, or glass are engraved, or may provide an intaglio printing plate, of metal, for printing images on paper as prints or engravings. Engraving was a historically important method of producing images on paper, both in artistic printmaking, and in book and magazine illustration. It has long been replaced by various photographic processes in its commercial applications and is much less common in printmaking than etching and other techniques.