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 he wants a
line to appear in the finished piece, so exposing the bare metal. The plate is then dipped in a
bath of acid, 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.
Aquatint is an intaglio printmaking technique, like etching, aquatint uses the application of
acid to make the marks in the metal plate. Where the etching technique uses a needle to make
lines that print in black (or whatever colour ink is used), aquatint uses powdered resin which
is acid resistant in the ground to create a tonal effect. The tonal variation is controlled by
the level of acid exposure over large areas, and thus the image is shaped by large sections
at a time.
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. 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.