Etching is one of the more complicated and interesting printmaking techniques. By definition, an etched surface has been "eaten away" by some medium.  For metal surfaces, the most usual medium is acid of some variety.  I use zinc plates and etch the surface of  the plate with copper sulphate which is a safer alternative to any of the traditionally used acids. Etching was invented in Germany and the Dutch artist, Rembrandt, is credited with having further developed the technique of etching or 'intaglio'. His work shows a mastery of this technique which has changed very little since he produced his prints in the17th century.
The metal plate is covered with an etching "ground" which has a water-repellent wax base.  The design is drawn into the etching ground using a fine needle point.  The plate is then placed into the carefully mixed acid (or safer alternative such as copper sulphate) which eats away the metal in the places where the wax surface has been scratched to reveal the plate underneath.
When I feel the lines are etched deeply enough, the plate is cleaned to reveal the etched design.  The plate is inked, wiped off and printed through an etching press on to damp paper and the first print is pulled. This process can be repeated many times on each plate until the artist is happy with the image. Then the edition can be printed. I often add colour to my printed etchings with watercolour paint and  limit  the edition to 40 prints or less. 

Eucalyptus preissiana etching
‘Eucalyptus preissiana’ with completed etching

todtiana edit 2.08
Hand coloured etching  'Eucalyptus todtiana'
with the seed pods used to draw the design

STAGES ETCHING A PLATE    'Quandong' height 12cm x width 15cm

Stage 1 is line etching, drawing the image on the plate.
I didn’t print this stage, although I would do so with a
more complicated image

Quandong stage001
Stage 2
Aquatint added to the line etching

Quandong stage002
Stage 3
Plate is burnished on some surfaces to flatten the aquatint
and lighten the tone. Background lines and plate texture added.

Quandong stage003
Stage 4
Lines etched on fruits for more tonal contrast

Quandong stage004
Stage 5
Open bite and more aquatint, putting tone on the
background leaves and adding strength to the
branches and fruits. I decided to print the edition
using Burnt Umber ink