Series editors' preface - Wood Tools

148 Conservation of Furniture
blood and saffron. Pacheco (1649), Cennini
(Thompson, 1960) and other well-known
period sources all give such recipes, many of
which were highly coloured with madder,
indigo or other dyes to be applied over metal
leaf or paint.
The process of distillation necessary for the
production of solvents was known to the
ancient Greeks but not extensively or efficiently
employed. Purified alcohol was widely
available in Europe after the twelfth century.
Various volatile essential oils such as ‘oil of
spike’ (spike lavender) and ‘spirits of turpentine’
(distilled from conifer resins) were also
being prepared in Europe by the late fifteenth
or early sixteenth centuries. Several clear resins
could be dissolved in ‘spirits of wine’ (ethanol)
including shellac, sandarac, mastic, gum benzoin,
accroides and the brightly coloured red
and yellow resins dragon’s blood and gamboge.
A smaller number, such as mastic and
dammar, could be dissolved in turpentine.
Turpentine was the primary solvent used to
thin out both drying oils and oil–resin
varnishes.
Until the end of the eighteenth century, the
relatively high cost of alcohol soluble resins as
well as the expense of the solvent confined
these ‘spirit varnishes’ to such rarefied and
time-consuming crafts as japanning and the finishing
of small decorative objects. The technique
of ‘French polishing’, by which
shellac-based varnishes are applied with a
cloth pad in a complex series of operations,
was probably not developed until the early
years of the nineteenth century when both
shellac and rectified alcohol became more
commonplace. It is worth noting however that
shellac must have been available from at least
the late seventeenth century since it is referred
to by Stalker and Parker as being unsuitable for
varnishing. The application of shellac with a
pad creates a surface coating known as French
polish. This finish technique has its origins in
an eighteenth century process called French
polishing which used bundles of abrasive equisetum
stalks called a ‘polissoire’ and wax to
create a high gloss finish (Halee, 1986; Mussey,
1982a). By the early nineteenth century,
obtaining a high gloss finish with a pad and
shellac became the preferred technique. In an
1827 American finisher’s manual, it was noted
that friction, or French polishing, was ‘of com-
paratively modern date’ (Mussey, 1987). The
Mechanic’s Register (1837) claimed that ‘We
were the first to publish any accurate information
on the “French Polish” for wood, now
become so universally employed’. It has been
a part of the finisher’s and restorer’s trade ever
since. For further discussion on the introduction
of ‘French polish’, see Penn (1984).
Synthetic polymers became available as coating
products toward the close of the nineteenth
century with the introduction of cellulose
nitrate. This and the products that have followed
in the twentieth century are synthetic
materials intended as improvements on traditional
natural materials. These products vary
greatly in chemical make-up. They can be
found in transparent coatings, paints, and other
finishing materials. In general, synthetic resins
are high molecular weight long chain or network
polymers. Synthetic resins that have been
used as coatings on wood include alkyds,
urethanes, phenolics, polyesters, epoxies,
methacrylates (acrylics), ketone resins and cellulose
nitrates.
4.4.5 Gilding
The term gilding usually refers to the process
of covering a surface with gold or other metal
leaf in imitation of solid metal. The range and
characteristics of metal leaves are described in
section 5.5. There are several methods by
which they can be attached and these are
described more fully in Chapter 14. Historically,
there are two processes described as ‘oil
gilding’ and ‘water gilding’ by which the
extremely thin metal leaf may be attached to
the surface to be gilded. Oil gilding uses a very
thin layer of oil-gold size as the adhesive to
attach the leaf and can be carried out on virtually
any surface though the full effect of the
gold is only achieved on well-prepared smooth
surfaces. Oil-gold size contains principally linseed
oil with the addition of copal varnish to
promote thorough drying of the film and to
prevent the size from forming runs, and turpentine
to achieve the desired viscosity. A very
thin coat is applied with a brush onto the surface
to be gilded. Porous surfaces are best isolated
by, for example, a shellac coating to
prevent excessive or uneven absorption of the
size and loss of adhesion. Water gilding uses
water to activate the glue size in the surface