GUIDELINES FOR THE CURATION OF GEOLOGICAL MATERIALS

adequately heated and ventilated. Where inappropriate conditions are suspected,
such as major temperature fluctuations (i.e. 5-10 centigrade degrees over two to
three hours), relative humidity (rh) below 35% or above 65% for any but very
short periods, atmospheric pollutants presents, gases or dust, environmental
monitoring and control should be introduced. It may be advisable to utilise some
form of environmentally controlled chamber for storage of specimens in the work
area. For sulphides that are easily oxidised, and other materials sensitive to high
rh, the use of silica gel (either dry giving 10% rh, or conditioned to give up to
60%) as desiccant or moisture buffer may be necessary. Conversely where a high
relative humidity is required, this can be achieved in a simple chamber using
water or a saturated salt solution (see Howie 1979b and Waller in press) The
latter gives greater control of humidity but requires constant maintenance to
prevent salt creep within the chamber, which may cause contamination. Where
humidities are kept in excess of 65% to 70% a vapour phase fungicide, e.g.
thymol, may be used to control mould growth within the chamber. Processing
areas require a good level of lighting, although certain photo-sensitive materials
may required protection (see C2.4.1).
Within the definition of processing we include the preparation of geological
material which can be described as the physical modification of specimens for the
purpose of realising the maximum potential use of the material. The extraction of
microfossils, cleaning of minerals, cutting and grinding thin sections, mechanical
and chemical development of macrofossils are all forms of preparation designed
to enhance the scientific, educational or display value of the specimens. The
researcher or curator should always maintain a responsible balance between the
objectives of specimen preparation and the requirements of conservation. (See
E2 Preamble).
In the interests of specimen preservation, the use of non-destructive methods of
examination (e.g. radiography) should be considered, whenever possible, as
alternatives to specimen preparation. Removal of supporting matrix often
weakens specimens and necessitates the use of consolidants or other synthetic
supporting media, which may themselves cause conservation problems at a later
stage.
The objective of specimen preparation, including cleaning of minerals, should
be carefully considered. The type of material selected and the nature of the
preparatory treatment adopted should reflect the requirements of the use to
which the specimens will be put. The visual enhancement of a macrofossil for
display, for example, may involve a different approach from the exposure of its
diagnostic features for taxonmic research. The preparator should understand the
characteristics of a specimen, and its intended use since the material is at greatest
risk while in his hands.
Fossils
Preparation
(1) Field methods. The conservation of fossils should start during their excavation.
Damage caused by poor procedures or materials may be diffcult to rectify
during later laboratory processing. It is most important to use reversible
treatments for the consolidation of wet or loose sediments and specimens in the