Series editors' preface - Wood Tools

tion will need to be reduced accordingly. An
excessively strong concentration of citrate can
damage oil gilding (see section 11.5.3).
16.9.4 Removal of overgilding
The opportunity to uncover original gilding that
has been overgilded, often with intervening
gesso layers, is encountered with some frequency
because restorers in the past often found it easier
and more profitable to regild an object than
to carefully clean and patch the original.
Microscopy, both reflected visible light and UV
light combined with staining, can be used to
characterize the stratigraphy and class of binding
media. This can help the conservator select a
treatment to remove upper layers whilst minimizing
the risk of damaging original material
below. The removal of one or more subsequent
layers of gesso, bole and leaf will restore legibility
to carving although other factors such as the
historical importance of the upper layer/s and the
overall condition of the underlying layer must
also be considered. Conservators of polychrome
sculptures with several generations of paint have
often considered which layer to present.
Hanlon (1992) reported the use of aqueous
poultices to swell water gilding that had been
applied over an original oil gilded surface. The
poultices gave a degree of control over the
penetration of moisture into the gesso layers
and facilitated the mechanical removal of the
softened gesso. Polar chlorinated hydrocarbons,
such as dichloromethane, can be used to
remove oil gilding that has been applied over
water gilding. Dry stripping of overgilding may
utilize any sharp flexible tool such as a scalpel
or a leather worker’s bent awl (Green, 1991).
Tools made of ivory, bone or Perspex
(Plexiglas) are hard enough to do the job and
can reduce the risk of damaging an original
surface. Dry stripping is time-consuming and
usually carried out where the burnished water
gilding forms the original substrate because
this provides a poor adhesive bond to subsequent
layers. Dry stripping may not be successful
where oil gilding or textured gilding
forms the original decorative layer.
16.9.5 Removal of bronze paint
Although bronze powder has a long history of
use in the creation of decorative surfaces,
Conserving other materials II 773
Figure 16.27 Detail of darkened and discoloured brass
particle (‘bronze’) paint on a nineteenth century gilded
picture frame
including japanning and stencilling, it is often
encountered in the context of poor quality
restorations on gilded objects. Bronze paint,
sometimes called gold paint, usually consists of
brass powders that may have been bound in a
variety of vehicles (oil-based, resin-based, cellulose
nitrate etc.). Bronze paint has often been
applied to gilded surfaces during previous
restoration attempts in order to compensate for
losses or to brighten up the appearance of the
surface. Removal is problematic when the solubility
parameters of the bronze paint binder
overlap with the mordant used in the original
gilding, for example when oil-based bronze
paint has been applied directly onto an oil
gilded surface. Bronze powders or paint
should not be used on gilded surfaces because
they tarnish and discolour over time (Figure
16.27).
It is important to characterize the solubility
of the bronze paint vehicle and the underlying
gilding in order to assess whether the bronze
paint can be removed with solvents. Bronze
paints bound in a cellulose nitrate medium are
soluble in acetone. Buck (1993) reported success
in removing bronze paint from both water
and oil gilded surfaces using solvent gels and
considered the use of an aqueous cleaning
solution that incorporated a chelating agent.
16.9.6 Consolidation
A gilded surface is vulnerable to damage from
wear, abrasion and breakage. Aside from these,
major categories of gesso damage include
delamination from the substrate, delamination