Series editors' preface - Wood Tools

11
Principles of cleaning
The cleaning of furniture has always been an
important part of housekeeping and the
restorer’s trade (Hale, 1853). In the past, a
variety of concoctions for cleaning furniture
have been recommended, ranging from a
dampened cloth to ground glass or stale beer
and vinegar. Few were selected with any
degree of specificity to the nature of a particular
surface. The conservator’s objective is to
balance the removal of unwanted material
from an object with the preservation of the
varnish or decorated (e.g. painted, japanned,
gilded or lacquered) surface.
This chapter identifies options for the cleaning
of varnished and decorated surfaces on
furniture and wooden objects. Although the
theory of cleaning is discussed under four
separate categories (mechanical, solvent,
chemical and aqueous cleaning), in practice
these approaches are often combined. The
theory and practice of cleaning is central to
much conservation research and it is essential
to keep abreast of current developments.
The term cleaning often has a fluid meaning
in conservation. The term cleaning refers to
the removal of unwanted accretions, such as
dirt, which obscure a surface. In the context
of decorated surfaces, other treatments may
also be called cleaning but it is more accurate
to refer to them as ‘removal of varnish’ or
‘removal of overpaint’.
Surfaces are important because they contain
much of the value of the original object. This
value may be aesthetic, historical, informational,
spiritual, monetary or a combination of
these. Varnished or decorated surfaces on
furniture are very vulnerable to damage. They
are usually thin, subject to the greatest wear
and tear in use, and are at the front line of
environmental change. It is convenient to
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discuss surfaces separately from the wooden
substrate because they are manufactured using
different skills and techniques to those usually
associated with cabinetmaking and because,
although different in appearance, decorated
surfaces share a similar fundamental structure.
It must be remembered, however, that surface
and substrate form an integrated whole and
often in practice cannot be treated independently.
Many defects such as flaking paint and
gesso, for example, have their origin in the
movement or chemistry of the underlying
structure. Coatings can be responsible for
unequal moisture movements in wood and
can lead to warps, cracks and splits, which in
turn result in damage to the varnish or decorative
layers. Structural treatment of the wooden
substrate is often constrained by the presence
of coatings and vice versa.
Up until the twentieth century, the range of
binding materials that were included in
decorative surfaces was comparatively small.
Materials used to create decorative surfaces on
furniture include not only those found in other
disciplines such as easel painting and
polychrome sculpture but materials derived
from a vernacular tradition, such as the use of
beer as a binding media in simulated wood
grain. The range of possible constituents of
decorative surfaces has vastly increased in the
twentieth century, particularly after 1945.
Using painted surfaces as an example, not
only have new materials such as alkyd resins
and acrylics come into wide use but a huge
range of materials such as thickeners and
gelling agents, biocides, dispersion aids, UV
absorbers, flame retardants and corrosion
inhibitors may be added (see, for example,
Rothenberg, 1978). These materials will
complicate analysis and affect the solubility