GUIDELINES FOR THE CURATION OF GEOLOGICAL MATERIALS

within the scope of provincial museums. Others, such as X-ray diffraction, SEM
preparations, Radiometric determination etc., are the realm of the highly
equipped laboratories of major research institutions. Information about many of
these processes may be found in Allman & Lawrence (1972), a good starting
point for further reading.
REPLICATION
The preparation of peels from specimens, and the moulding and casting of
geological material present few problems for the majority of specimens if effective
measures are taken to protect friable or delicate surface structure. Peels, pulls
and moulds should not be considered as permanent records, although modern
glass reinforced plastic casts are extremely robust and long-lasting, and can
faithfully replicate the finest surface detail. For many purposes, e.g. exhibition,
study, exchange, casts of fossils may be acceptable in placed of the real thing.
Detailed methods for the preparation of peels, moulds and casts are given by
Rixon (1976) and Waters (1983).
Safeguarding specimens during moulding
Specimens must be very carefully inspected before any attempi is made to begin
the moulding process. Those with a porous or highly indented surface will need
some form of superficial hardening, to prevent the moulding compound from
adhering. The same applies to those with a flaky or chalky surface. One of the
most useful temporary surface hardenerlseparators is a 5% aqueous solutiofi of
polyvinyl alcohol, which combines both in one application, and can be painted on
thinly enough not to obscure surface detail of the specimen. It also has the
advantage of being water-soluble and so can be simply washed off afterwards. It is
available both in a clear form and with a fugitive blue dye which is useful on, for
example, large, dark or flat surfaces in order to indicate whether or not total
coverage has been achieved. Any cracks or holes in the specimen must be filled so
as to prevent the moulding compound from running in and breaking off when the
mould is removed and home-made 'water soluble plasticene' can be used for this
purpose. This is basically a mixture of water soluble carbo-wax (polyethylene
glycol 1500), precipitated chalk and glycerol. This too can be washed off after
use. Teepol (a neutral pH, liquid detergent) can be used on robust specimens and
as this acts as a surface-wetting agent, rather than a real separator, care must be
exercised to ensure the surface of the specimen is strong enough to accept the
moulding material it is desired to use.
Materials
Cold cure (or RTV) silicone rubbers, in various forms, make up the majority of
moulding compounds most readily used today. Dow Corning RTV 9161 Silastomer
is an old favourite and still widely employed on slightly fragile specimens as
it tends to tear easily, which is preferable to breaking the specimen. Wacker RTV
533 is much stronger and can be used on robust specimens. RTV 533 is useful for
skin-moulds as it does not need the application of a gauze bandage for added