is an intaglio printing process in which an etching needle is used to draw into a wax ground applied over a metal plate.

The plate is then submerged in a series of acid baths, each biting into the metal surface only where unprotected by the ground.

The longer the plate is exposed to the acid, the deeper the bite and therefore the stronger the line.

The ground is then removed and the plate inked. The smooth surface is wiped of ink before printing, though some ink may purposely be left on the plate for tonal effects.

Considerable pressure is used in the press
to force the ink out of the lines and areas and, to an extent, to force the paper into them, so the final printed image will appear to be slightly raised above the surface of the uninked paper.

Glass etching uses a similar technique where an etching cream or solution is used to bite into the glass. The method however is different since the drawing is painted on in negative with a resistant.

When thoroughly dried, the etching cream is applied. When done the glass is cleaned and a nice etched drawing remains.

Nowadays a similar effect can be obtained by using an etching spray with a stencil. The spray does not bite into the glass but allows for a similar look.

The appearance of etchings is usually free and spontaneous but the technique has occasionally been used to produce results almost as formal as engraving.