Series editors' preface - Wood Tools

144 Conservation of Furniture
bole or bolus is derived from the Greek, meaning
‘clod of earth’, as the clay that was first
used for this purpose came from deposits in
the ground. Armenian bole was considered to
be the best. It is composed of pipe clay
(hydrated silicate of aluminium and organic
sediments) and iron oxides, which give it its
distinctive blood-red or orange colour. It may
now be difficult to obtain.
The colours used depended upon the clay
deposits that were locally available so that, for
instance, the red clay on seventeenth century
Spanish work is a different colour to French
red clay of the same period. In later centuries,
when individual clay deposits were no longer
exclusively relied upon, fashion played a role
in determining the clay colour. In nineteenthcentury
English gilding, for example, a dark
blue/black clay was often used under burnished
water gilding whilst in the last quarter of
the eighteenth century a pinkish brown clay
was common. The clays were made using a
number of different ingredients, ranging from
bullock’s blood to soap. These additives gave
varying characteristics but the base constituents
remained pipe clay and pigments.
Today, bole comes in many colours and is
most often sold in the wet state, but it can also
be purchased in a more limited range of
colours in the dry cone form. Modern commercially
produced boles are manufactured
from pipe clay combined with a colouring
agent and water. A few contain an oil or lead
to further facilitate the burnish but in most
cases it is left up to the gilder to add a little oil
if required.
Bole is made by mixing clay with warmed
parchment size, rabbit-skin size, fish glue or
glair and applying with a soft brush onto the
prepared gesso surface on which the leaf is to
be laid. Glair is derived from egg white (see
section 14.2.13). Two distinct layers of bole
may often be found on the same piece. A yellow
ochre bole was applied directly on the
gesso, to hide any breaks or ‘faults’ in the gilding
by virtue of its colour. Over the yellow
bole, there may then be a second bole made
of clay of a deeper colour to which beeswax,
tallow, oil, suet or graphite may have been
added to enhance its burnishing capabilities.
Souza and Derrick (1995) has shown cross-sections
of Brazilian polychrome sculptures in
which graphite particles can be seen lying par-
allel to the surface of the bole. This second
layer of bole is applied to tone the colour of
the gilding, and to serve as a soft ‘seat’ (assiette
in French) which deforms under an agate
burnisher to take a high polish. Bole is discussed
further in Chapter 14.
Composition
There are numerous recipes for composition
and the term is used to cover many forms of
raised decoration including papier mâché and
‘pastiglia’. However, the traditionally accepted
form of ‘gilders’ compo’ is a mixture of resin,
linseed oil, animal glue and whiting. Ornament
is created by pressing the warm, dough-like
composition into reverse-carved moulds of
boxwood or fruitwood (Thornton, 1985).
When released from the mould the composition
will have taken on the detail, however
fine, of the mould. At this stage it is pliable and
easy to cut enabling the ornament to be placed
onto curved surfaces or into corners. Once dry,
composition is hard and brittle and cannot be
cut into or carved without the material splintering
or shattering. Though composition itself
is very durable, shrinkage can be a problem
and regular breaks and gaps are a common
feature in this type of ornament. As it shrinks
and breaks it sometimes also curls away from
the support.
4.4.3 Paints and paint media
When present, paint usually carries a vital part
of the information the artist, designer or craftsman
wished to convey. Paints consist essentially
of a pigment, a film-forming medium or
binder, and a liquid component composed of
solvents and diluents that makes the mixture
more or less fluid during application. Together,
the film-forming and liquid components are
often called the vehicle. Various additives may
be used to give coatings additional structural or
aesthetic properties. Many of the materials
used to make transparent coatings are also
used to make paints. Due to the presence of
pigment particles, opaque coatings are generally
more stable than transparent coatings (Roff
and Scott, 1971) and generally provide better
protection of the substrate due to the more
complete exclusion of light, moisture and
environmental fluctuations. A harmonious relationship
between the ground, the pigment and