Used in the past to engrave designs onto amour, guns and plates, it is now used in industries to make prints.
In etching, a metal 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 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 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 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.
