Series editors' preface - Wood Tools

solvent creeping behind or underneath the
surface of the glass that is being cleaned. The
frame or surround should be protected from
cleaning solutions; Melinex/Mylar may be
inserted into the rebate between the glass and
frame for this purpose. Aqueous or solvent
cleaning should be avoided if the glass is
cracked because dirt will be drawn into the
cracks by capillary action. The traditional
method of cleaning glass was to add a little
vinegar or ammonium hydroxide to water.
Raising pH slightly, with a drop of ammonium
hydroxide, will saponify grease and oil and
make it water-soluble. A cleaning solution
with an excessively high pH may attack the
silica in the glass. Consideration should be
given to the potential for damaging adjacent
materials or finishes if pH is adjusted. A pH
of 5.5–8.5 is broadly accepted as safe for many
organic surfaces. Adding a drop of a non-ionic
detergent (e.g. Triton XL-80N) will also assist
in bringing oil and grease into solution but as
detergents are non-volatile, a clearance procedure
will be necessary (see section 11.5.4).
Wiping over the surface with a swab
dampened with deionized water should be
sufficient to remove detergent residues from
glass. Solvent cleaning may utilize IMS,
acetone, 50/50 water and IMS, or white spirit.
Proprietary window cleaning products should
be avoided because the constituents are often
unknown. Spray application is inappropriate
because of the risk of damage from the
inevitable overspray. Proprietary abrasive
pastes generally contain particles of alumina
or silicon. These abrasives are not suitable as
they are too hard and will scratch the glass. A
home made paste may be made from whiting
and deionized water, to which a drop of dilute
ammonium hydroxide may be added if necessary.
15.5.8 Cleaning mirrored and decorated
glass
Painted and gilded surfaces that are well
adhered may be cleaned with a soft brush and
vacuum cleaner. Gilded glass has usually been
water gilded and aqueous cleaning should
therefore be avoided. The use of solvents with
a hydrogen-bonding component, such as
alcohol, should also be minimized. Davison
and Jackson (1985) have considered the
Conserving other materials I 709
conservation of reverse painted glass and
mirrors. Caldararo (1997) discussed the treatment
of paintings on ceramics and glass.
Tin/mercury surfaces should not be
vacuumed because the mercury will be vaporized
and expelled into the ambient environment
where it will present a health hazard. A
soft brush, used only for mirrored surfaces and
stored in a plastic bag, may be used to lightly
brush over the surface. Mercury may be
collected using a mercury salvage kit (e.g.
Chemizorb Hg, available through Merck) and
disposed of in accordance with current guidelines
or legislation. Mercury sponges are not
recommended for use on mercury amalgam
surfaces as they are not particularly effective
for this application and may cause damage.
Silvered surfaces are usually sealed with paint
and, if well adhered, may be vacuumed.
15.5.9 Repair of glass
Cracked or broken glass should be referred to
a specialist for repair and adhesive bonding.
Such treatments are difficult and require
experience and skill. A glass conservator may
be able to cast infills or readhere chips using
techniques developed for vessel glass,
although such treatments are usually only justified
for small areas on very valuable mirrors
(Jackson, 1984). Whilst reproduction glass is
available from a few specialist companies, it is
difficult to match the replacement to the
original. Bevelling and cutting complex shapes
was previously done by hand. Copying it is
often beyond the skill of glaziers and may
require the skills of a glass conservator. Repair
of painted, gilded or mirrored glass presents
additional difficulty, as there is the potential
that adhesive used to bond the glass may
creep between the glass and the painted or
mirrored surface, disfiguring it.
15.5.10 Consolidation
Flaking on painted, gilded or mirrored surfaces
should be referred to a specialist with experience
of painted glass, as the association of
these materials can present particular
problems. The decorated surface itself is often
complex, a wide variety of binding media may
have been used and problems are often
complicated.