Whatever
the method, the most important thing is that the wood grain must be
made very smooth and coated with "gesso". This is a preparation
used for some thousands of years by artists and craftsmen alike all
over the world. It is the only suitable ground for tempera painting
and it consists of gilder's whiting, rabbit skin glue and a few drops
of boiled linseed oil. It can be purchased in good art shops and directions
for use are supplied with the whiting and size.
Briefly,
the first task is to prepare the rabbit skin size in a glue pot or
double walled saucepan, add some cold water, stir and allow to stand
overnight. Warm to 65° C (1500 F), and stir until dissolved.
Do
not boil. Add the gilder's whiting and mix well together with a piece
of wood to get rid of all lumps, when the gesso should have the consistency
of ready-mixed paint. Add two or three drops of linseed oil and stir
well. Keep the preparation warm, and it is ready for use.
Apply
it to the wood with a hog-hair brush, preferably a flat one. For oil
gilding four coats of gesso are required, while for water gilding
it is necessary to apply eight coats. Though each coat must be dry
before the next is laid, all coats must be completed in one day. If
they are laid properly, nothing needs to be done to the final coat.
Gesso, by its nature, is very smooth, but nothing must be left on
the ground that would irritate or tear the gold, which, it will be
remembered, is only 1/250,000th part of an inch thick. If the surface
is not perfect, gently rub flour glass paper on the rough parts. If
too much gesso has come to rest in the hollows and other parts it
must be removed with a modelling tool or an old piece of linen dipped
in water. This has to be done very carefully, bearing in mind that
the gesso surface must be retained.
The
next stage is to apply Armenian bole to the surface if a really bright
surface is aimed at, but this is not essential. The Armenian bole
can be replaced by one coat of Lefranc "Mixtion a dorer"
which is an orange coloured oil gold size ready for use and available
from gilding supply shops. Stir the size well, and with a flat hogbrush
go over the surface thoroughly, making sure all is covered. Ensure,
too, that the surface is covered with the minimum amount of gold size.
This must be stressed, because any suggestion of a puddle in the hollows
or surplus on the higher parts will cause uneven dry-outs. Furthermore,
if the gold leaf is put on such surfaces, it would never be permanent.
Cover
up the work after sizing to prevent dust sticking, and from time to
time test for tackiness by touching the gold size lightly with the
finger, until it almost holds the finger in position (12 to 18 hours).
The drier the better.
