Series editors' preface - Wood Tools

498 Conservation of Furniture
(a) (b)
Figure 11.4 Varnish removal with a solvent gel
(a) Detail of the hood of a tall case japanned clock, attributed to Gawen Brown, Boston, late eighteenth century.
The elaborate japanned decoration was completely obscured by restoration varnishes that had darkened. The detail
shows the cleaning test using a solvent gel
(b) Faux turtleshell japanning revealed by removing discoloured restoration varnishes with a solvent gel
Testing a proposed cleaning system is an
important step in establishing the risks and
benefits of the treatment. A test area should
be examined under low magnification, using a
microscope or hand loupe, before and after
cleaning, to assess the impact of treatment.
Any swabs used in cleaning tests should also
be examined for evidence of the type of
material that is being removed (or not).
Tests should be undertaken in a systematic
way. Materials and techniques should be
tested on a small, inconspicuous part of an
object, such as the back of a leg or the
underside of a drawer front, to avoid damaging
the object and wasting time. Uniform
behaviour over a whole surface should not
be assumed because tests in one area have
been successful. A varnished or decorated
surface may not respond uniformly to a
cleaning system as a result of different treatments
in the past, non-uniform thickness of
varnish, differential degradation (for example
parts of the object may have received more
or less exposure to light), or the effect of
different pigments on the binding media.
Cleaning may result in components in a
ground or other layer being deposited on the
surface or in the craquelure, resulting in a
whitish appearance. This will not be apparent
by examining test swabs but viewing test
areas under low magnification should identify
this problem before cleaning begins.