After all ground has been removed from the
plate, its surface is inked and good care taken
that the ink penetrates into the incisions made.
The ink normally used is dense but ductile, made
of linseed oil and soot for black ink or
pigments for colour ink, and either mixed or
purchased in a specialised shop by the printing
artist. After the ink has been applied to the
plate, any excess ink should be wiped from its
surface, so that only the incisions making up
the image are filled. This operation can be
carried out either using cotton wads for
delicate sketches or tarlatan wads. A veil on
the surface, especially around the incised
lines, known as ink entrapment is achieved by
gently passing a tarlatan wad over the grooves
so that the ink they contain spills across its
edges. Special effects may be achieved by
strengthening or softening some of the lines, as
Whistler did in his work (IMATGE whistler.jpg)
in the 19th century.
If prints are struck in colour, several
procedures may be followed. Most traditional is
“a la poupée”, which consists of adding all
colours at the same time to the printing plate,
using different wads while applying each colour
in the proper area. This process turns each
print into almost a unique one, due to the fact
that it is impossible to control the borders
between different colours in consecutive pulls.
Printing may also be done with different plates
for each colour, with an exact record of their
placing so that each colour is applied in the
right spot and one on top of the other.
Alternatively engravers may use a more modern
and more complicated system conceived by S.W.
Hayter which carries his name. It consists in
applying different depths of incision to the
printing plate, each colour being applied with
ink rollers of different toughness so that a
print of various colours is achieved with a
single run through the printing press.