To etch is to corrode metal with acid. In order to control and confine the action of the acid, for instance when sinking a line into a metal plate, the line must in some way be both isolated and exposed. This is done by first protecting the plate with an acid-resistant coating or ground, usually wax on the front or working surface, and varnish on the back. A line is drawn cleanly through the wax ground, onto rather than into the metal with a light point or needle. The plate is then immersed in a bath of acid solution and the exposed line is "bitten" into the plate. The depth of the line depends mainly on the strength of the solution used and the length of time the plate is allowed to etch.
After etching, the plate is cleaned with a solvent and a thick ink is worked down into the etched areas. By repeatedly wiping across the surface of the plate evenly, in all directions, the ink is cleaned from the plate, except in the etched areas. The wider the bitten line, the less it will retain ink and the paler it will print.
To make the printed impression, the plate is set face-up and centrally on the flat metal bed of a copperplate or "intaglio" printing press. The bed is moved slowly and smoothly between two heavy rollers that carry the softened paper over the etched plate. The paper is thus forced into the ink-filled lines, and when taken from the press retains an exact, but reversed, image of the plate surface - inked and embossed.
Each time a new print is made, the plate has to be re-inked, wiped and again taken through the press.

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