Series editors' preface - Wood Tools

710 Conservation of Furniture
The consolidation of flakes on a mercury
amalgam mirror may be problematic as the
oxidized tin layer is very brittle. The traditional
method of laying a flake by applying consolidant
under the flake and then adhering it to
the substrate with a heated spatula is not
appropriate for mercury amalgam surfaces.
The application of pressure to the flake will
break or shatter it. In addition to problems
with appearance, the crystal structure of the
mercury amalgam phase has an upper limit of
58 °C (Hadsund, 1993). In some cases the
application of a small amount of consolidant
to the thin edge of a flake may provide a
bridge that secures the flake in place. Such
consolidant should be very viscous (e.g. 50/50
w/v Paraloid B72 in acetone). If this procedure
is undertaken the minimum amount of
consolidant should be used and it should not
end up under the flake.
Techniques for consolidation of the painted
layer of reverse painted glass are unlike those
used in painting conservation. The glass is an
inflexible support of a very different nature to
canvas or panel paintings. Traditional methods
of varnishing the reverse or injecting voids
with resin have usually been unsatisfactory
and, due to shrinkage of the consolidant, may
have exacerbated the problem. Refixing flakes
of detached paint is a specialist task that
should be referred to a conservator with
experience of reverse painted glass.
15.5.11 Restoration and retouching
The use of metal foils to patch areas of loss
is inadvisable because of the probability that
the mercury will react with the repair material
and that galvanic corrosion will occur (see
section 8.4). Jackson (1987) used a technique
in which mirrored Melinex/Mylar sheet was
laid behind the mirror to disguise areas
where the amalgam had been lost. A similar
technique may be used for areas of loss on
reverse painted glass. A coloured background
acid free paper, tinted with water colours if
necessary, may be laid behind the reverse
painting for small areas of loss. Larger details
may be painted onto a sheet of Melinex/
Mylar and positioned so that the replacement
is aligned with the original design. This
should be secured to the backing and not the
glass.
15.5.12 Coatings
Coatings are not appropriate for undecorated,
reverse painted or mirrored glass. The application
of a coating to a mercury amalgam
surface is not recommended. The deterioration
of tin/mercury mirrored surfaces is irreversible.
Blackened areas result from the separation of
the tin/mercury amalgam into constituent
components followed by oxidation of the tin.
Impregnation or coating with a resin will not
slow down or prevent this deterioration and
cannot prevent crystal growth or other changes
in the amalgam. Further, attempts to remove
such a coating in the future are likely to
damage the amalgam surface. The most effective
way of ensuring longevity to mirrored or
decorated glass is to ensure that it is protected
from physical and environmental damage.
Bibliography
15.1 Ivory, bone, antler, turtleshell,
horn and mother-of-pearl
Bitmead, R. (1873) The London Cabinet Maker’s Guide,
London
Davison, S. (1998) Reversible fills for transparent and
translucent materials, JAIC, 37(1), 35–47
Down, J.L., MacDonald, M.A., Williams, J.T. and Williams,
R.S. (1996) Adhesive testing at the Canadian
Conservation Institute – an evaluation of selected
poly(vinyl acetate) and acrylic adhesives, Studies in
Conservation, 41(1), 19–44
Driggers, J.M., Mussey, R.D. and Garvin, S.M. (1991)
Treatment of an ivory inlaid Anglo-Indian desk
bookcase, in AIC Wooden Artifacts Group Conference
papers, Albuquerque
Espinoza, E.O. and Mann, M. (1992) Identification Guide
for Ivory and Ivory Substitutes, World Wildlife Fund,
Washington, DC
Hawkins, D. (1986) The Technique of Wood Surface
Decoration, Batsford
LaFontaine, R.H. and Wood, P.A. (1982) The stabilization
of ivory against relative humidity fluctuations, Studies in
Conservation, 27(3), 109–17
Lochhead, V. (1989) Tortoise-shell substitute veneer,
Conservation News, 38, 31–2
Matienzo, L.J. and Snow, C.E. (1986) The chemical effects
of hydrochloric acid and organic solvents on the surface
of ivory, Studies in Conservation, 31(3), 133–9
Mussey, R. (ed.) (1987) The First American Furniture
Finisher’s Manual, reprint of the 1827 edition of The
Cabinet-Maker’s Guide, Dover
Ramond, P. (1989) Marquetry, Taunton Press
Rao, S. and Subbaiah, K.V. (1983) Indian ivory, Journal of
Archaeological Chemistry, 1 (1), 1–10
Siddons, G.A. (1830) The Cabinet Maker’s Guide,
Sherwood, Gilbert and Piper