Series editors' preface - Wood Tools

(a)
(b)
(c)
cleaned area should be feathered to avoid
ridges of dissolved dirt or varnish because
once hardened, they may be less readily
soluble, more difficult to remove and will abut
a clean and sensitive surface.
Unvarnished surfaces, such as bare wood or
gesso, are more susceptible to damage during
cleaning and may be contaminated by the
cleaning material or displaced dirt (Figure
11.3). Exposed areas may be sealed before
cleaning commences, for example if the wood
was originally varnished or it is intended to
seal exposed gesso as part of the conservation
treatment. Pre-sealing will protect vulnerable
areas from cleaning materials and reduce the
possibility of cleaning solutions wicking under
coatings, causing discoloration, delamination
and other problems. The sealing material
should be compatible with other potential
treatments such as consolidation or recoating
and may be temporary or permanent, as
required. It may be possible to clean areas
before a sealer is applied, though in some
cases it will be necessary to consolidate and
then clean.
Principles of cleaning 497
Figure 11.2 Partial and selective cleaning
(a) Partial cleaning to reduce the thickness of unwanted
material
(b) Selective cleaning to remove unwanted material from
some areas of the substrate, leaving others untouched
(c) Detail of a painted wardrobe, English, c.1775. The
background is executed in oil paint, but the decorative
details have been painted in a solvent sensitive medium.
This surface has been cleaned in the past and small
areas of loss attest to the solvent sensitivity of the green
detail. Previous treatment involved selectively cleaning
darkened varnish from the background, leaving the
varnish on the green areas rather than risking further
loss
Figure 11.3
Detail of a
giltwood
barometer c.1740.
Repeated cleaning
of the silver
registration plate
in the past has
disfigured adjacent
gilding
11.1.5 Cleaning tests
Cleaning tests are an empirical method of
determining the solubility of unwanted material
and of establishing differences between the
solubility of the unwanted material and the
surface below. The aim is to establish which
solvents will remove unwanted dirt, varnish or
overpaint without affecting the materials
below (Figure 11.4). It is helpful to have
characterized the underlying surface and be
familiar with its solubility parameters before
conducting solvent tests to prevent damage
that may not be immediately apparent, e.g.
leaching or swelling of oil paint (see discussion
of solvents in section 16.6.3 on removal
of varnish).