CONSERVATION OF GEOLOGICAL SPECIMENS 377 allow such growth When an infestation is encountered the steps to take are: confine it; stop its growth; eradicate it; and prevent it from reoccurring Reduced Oxygen Environments Reduced oxygen environments are cost-effective lowimpact methods of controlling the deterioration of specimens that are sensitive to oxygen, water vapour, or pollutants Any rock or mineral specimen that is sensitive to oxygen, water vapour, or pollutants (such as rocks containing pyrite that is likely to oxidize or has begun oxidizing) can be stored in reduced oxygen environments to prolong their life There are three components to a reduced oxygen environment: an oxygen scavenger or oxygen-purging system; an oxygen monitor; and a barrier film Oxygen scavengers are composed of either iron filings or molecular sieves such as zeolite or mordenite The optimum composition of a barrier film for this purpose is currently under research Commercially available films are currently composed of materials chosen to suit either the food or the electronics industries, and, whilst these films may be useful for preventive conservation, they may not be the optimum Barrier films are layered polymers combined to produce a film with good tear strength, low water migration, and low oxygen migration The enclosure is made by wrapping the specimen in the barrier film and using a heat sealer to close the film and finish the encapsulation The specimen should be supported in conservation grade materials to ensure that no physical stresses are imposed on the specimen and no damage is created by the abrasion of the film on its surface (Figure 3) Remedial Conservation Remedial conservation consists mainly of direct action carried out on an object with the aim of retarding further deterioration One of the most important and sometimes controversial stages of conservation treatment is surface cleaning Irreversible damage can occur if inappropriate treatments are used However, the removal from the surface of the object of contaminants or old consolidants that may otherwise cause harm is highly advantageous For example dust can contain acidic particles that can cause surface damage In some cases cleaning may also clarify an object’s detail or reveal unseen damage that can be treated subsequently Joins that require repair also have to be surface cleaned to improve the final bond There are many types of surface-cleaning techniques available to the conservator, and they tend to be divided into mechanical cleaning and chemical cleaning Surface Cleaning: Mechanical Abrasive Abrasive cleaning methods include all techniques that physically abrade the fossil surface to remove contaminants or coatings Such techniques involve the use of materials that impact or abrade the surface under pressure, or abrasive tools and equipment The use of water in combination with abrasive powder may also be classified as an abrasive cleaning method Depending on the manner in which Color Image Figure Pyritised ammonite encapsulated in barrier film in an oxygen free environment