Series editors' preface - Wood Tools

166 Conservation of Furniture
Waxes show generally low bond strength and
are more commonly encountered as coatings
than as adhesives in woodwork. However, wax
and wax–resin mixtures have been used extensively
in painting conservation as adhesives for
lining canvases and have also been used to
consolidate biodeteriorated wood and to
secure flaking polychromy to wood substrates.
Waxes have also been used extensively as fill
materials in conservation where they have
been exploited for the range of hardness available
and the ease with which they may be
applied and levelled. Waxes are grouped
according to their origins as animal waxes,
plant waxes and mineral waxes.
Animal waxes
Animal waxes have been obtained from a great
variety of sources, of which the most important
are beeswax, shellac or lac wax, Chinese insect
wax, spermaceti wax from sperm whales and
lanolin or wool wax from sheep. Wax synthesized
by the honey bee (Apis mellifera) and
extracted from honey comb using hot water,
pressure or organic solvents, has the empirical
formula C 15H 51COOC 30H 61. It contains about
64% esters, 14% hydrocarbons and 12% free
fatty acids, a composition that is genetically
determined for each species and varies to only
a small extent. However, the use of paraffin
wax and stearin to make artificial combs may
lead to a ‘contaminated’ product. Beeswax
varies in colour from pale yellow to dark
greenish brown. Darker varieties may be
bleached using a variety of methods among
which the oxidizing acids tend to cause deterioration.
It also varies in texture being fairly
brittle when cold but plastic when warm. It
becomes markedly soft and susceptible to finger
printing at about 37 °C with a melting point
generally in the range 63–65 °C. Bleached wax
tends to be denser, more brittle and to have a
smoother fracture. Beeswax is the primary traditional
component of furniture wax polishes.
However, because its relatively low melting
point makes it prone to finger printing, it is
often used in conjunction with other waxes
such as carnauba and paraffin wax. Despite a
reputation for being freely soluble in a wide
range of solvents, there are in fact very few
true solvents for this material of which Horie
(1987) cites only chloroform and carbon tetrachloride.
Pure gum turpentine has been widely
used as a solvent for waxes in furniture conservation.
Toluene and xylene are probably the
best among a wide range of partial solvents. A
mixture of xylene and methanol (in unspecified
proportions) is available commercially as a
wax remover (Libnet ® by Liberon). Less toxic
substitutes may be found in a range of precision
cleaning fluids available from Merck of
which Dow Corning OS-120 fluid is an effective
solvent for wax. Beeswax has an acid
value (the number of milligrams of potassium
hydroxide required to neutralize the free fatty
acid in one gram) of 16–22. Another insect
wax, lac wax, a byproduct of the shellac refining
process, is occasionally used in furniture
finishes. Lanolin, which comes from the processing
of wool, is occasionally used on furniture
but more commonly on leather.
Plant waxes
A large variety of plant waxes exists, including
carnauba wax, ouricuri wax, candelilla wax,
esparto wax, Japan wax and jojoba oil. The
most commonly used plant wax is carnauba
wax which comes from the leaves of the
Brazilian palm tree Copernicia cerifera where
its function is to prevent moisture loss from the
plant. A major component is melissyl cerotate
(C 25H 51COOC 30H 61) but carnauba wax also contains
triterpenes and esters of long chain acids
and alcohols up to fifty-six carbon chains in
length. These long chains constitute a diagnostic
feature that can be used to distinguish carnauba
from beeswax. Carnauba is a dark
greenish brown hard and brittle wax with a
melting range of 83–86 °C. In the bleached
condition it is pale yellow. It will take a very
high gloss when rubbed but its high melting
point means that manual buffing is very laborious
and it is therefore often used as an additive
to increase the hardness of wax mixtures,
as are some hard natural resins. Carnauba wax
dissolves in pure gum turpentine and is also
affected, but to a lesser extent, by the solvents
listed for beeswax.
Mineral waxes
This category includes waxes obtained from
plant remains in various stages of decomposition
towards coal. Montan wax is extracted
from peat, and ozokerite and ceresine are
obtained by mining and processing lignite. As
these waxes have been altered over geological