Soft varnish

Soft varnish / Soft-ground etching

In pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid.
Soft-ground etching uses a special softer ground. The artist places a piece of paper (or cloth etc. in modern uses) over the ground and draws on it. The print resembles a drawing.
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.