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 widely used today.
In pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid.
The artist then scratches off the ground with a pointed etching needle
where s/he wants a line to appear in the finished piece, so exposing the bare metal. The echoppe, a tool with a slanted oval section, is also used for "swelling" lines.
The plate is then dipped in a bath of acid, technically called the
mordant (French for "biting") or
etchant, or has acid washed over it.
The acid "bites" into the metal, where it is exposed, leaving behind lines sunk into the plate. The remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, leaving only the ink in the etched lines.
The plate is then put through a high-pressure printing press together with a sheet of paper (often moistened to soften it).
The paper picks up the ink from the etched lines, making a print. The process can be repeated many times; typically several hundred impressions (copies) could be printed before the plate shows much sign of wear. The work on the plate can also be added to by repeating the whole process; this creates an etching which exists in more than one state.
Etching has often been combined with other intaglio techniques such as engraving or aquatint.
