Series editors' preface - Wood Tools

15
Conserving other materials I
This chapter introduces the principles and
techniques for the conservation of diverse
materials often associated with wooden furniture.
Each of these materials is a specialist
subject in its own right. It is essential that
conservators undertake further research,
consult references and seek specialist advice
rather than undertaking treatments on an
unfamiliar material. The conservator should be
as well informed as possible about these
materials and be alert for potential problems
in order to avoid causing irreversible damage.
15.1 Ivory, bone and antler,
turtleshell and horn, mother-of-pearl
15.1.1 Ivory, bone and antler
Ivory and bone are hygroscopic and
anisotropic. As a result they are prone to
warping and dimensional distortion in fluctuating
RH. Cracking is particularly associated with
low RH. Dimensional change in conditions of
fluctuating RH have been measured at around
4.2% along the radial axis, 1.5% along the
tangential axis and 0.5% longitudinally
(LaFontaine and Wood, 1982). Ivory and bone
are slightly porous and may absorb greasy
deposits, e.g. from handling or solubilized dirt
during cleaning. Ivory will yellow in the
absence of light. Antler is a modified form of
bone that is hygroscopic and will be damaged
by low RH, which may lead to cracking or splitting.
Split pieces may curl open. As a general
rule, the factors which affect the behaviour of
ivory have a similar effect on bone. Bone tends
to be harder and more brittle than ivory.
Organic components of ivory, bone and antler
will be attacked in excessively alkaline condi-
tions whilst excessively acidic conditions will
damage the mineral components. A pH ranging
between 5.5 and 8.5 should, as a general rule,
be maintained if aqueous treatments are used.
Ivory, bone and antler are very variable materials
and there will be exceptions to the generalized
information provided above. Ivory and
bone can be worked with woodworking tools
and can be machine or hand sawn, scraped and
abraded as required. Snow and Weisser (1984)
and Driggers et al. (1991) provide useful information
on the conservation of ivory. The material
properties and identification of ivory and its
substitutes are discussed in Chapter 5, Thornton
(1981) and Espinoza and Mann (1992) among
others.
Cleaning
Before cleaning ivory and bone, the surface
should be examined for the presence of original
varnish, dye, polychromy or gilding.
Ivory may have been finely engraved and
material found in engraved areas to highlight
the design is usually less vulnerable to damage
than that on the surface. Removal of surface
dirt and accretions is usually undertaken
before re-adhering loose pieces into place to
avoid adhering the dirt along with the ivory.
Abrasive materials should be avoided.
Cleaning tests are recommended to establish
the efficacy of the least potentially harmful
cleaning method. Plastic materials such as
celluloid and casein were used as ivory substitutes
in the late nineteenth and early twentieth
centuries and may be sensitive to both
aqueous and solvent cleaning. Cellulosic
vegetable ivory from the nuts of several palm
species may also be encountered. The autofluorescence
of these materials under UV is
discussed by Driggers et al. (1991).
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