The way objects within private or public collections are treated and cared for while on display is fundamental towards their overall survival. The objects may be made from a wide range of material, however, all basically fall into two main categories: organic materials, such as wood, cotton, leather or wool and inorganic materials, such as metals, stone and ceramics.
Each of these materials is influenced by surrounding physical and atmospheric conditions, but in different ways and degrees. There is then the problem of composite objects made of both organic and inorganic materials - such as books, furniture and fans.
Each material has its own characteristics and problems. However, organic materials tend to be more sensitive to the environmental factors. Relative humidity (RH), temperature, light, air pollution, dust, vibration, and the presence of salts are just some of the conditions that lead to damage. The following factors and conditions should be controlled before the items are preserved.
By managing the relative humidity around an object, you can control environmental damage and insect infestation. RH is the amount of water vapour present in the air and is expressed as a percentage of the maximum amount of water vapour that the air can hold at a specific temperature. Organic materials are best stored in stable or cooler conditions that prevent humidity and temperatures from promoting the growth of mould and insect infestation. Organic materials should be placed within a RH of 40 to 60 per cent RH. Inorganic objects should be stored in a stable condition, such as 35 per cent RH.
Temperature levels reflect RH. In a closed space, if there is no water vapour added to the air, RH drops as temperature rises and as a result can make objects brittle and dry. Similarly, if the temperature drops and the RH rises, there will be problems with moisture. It is therefore vital that temperatures are kept to an overall standard so that basic control can be achieved, since fluctuations are even more detrimental to the objects.
Light levels are measured in lux, an international system unit of illumination that is equal to one lumen per square metre. For example, a wax candle generates 13 lumens and a 100 watt bulb generates 1,200 lumens. Sensitive materials such as paper, watercolours, textiles and feathers should not be more than 50 lux. This is the lowest level that the eye can distinguish details accurately.
Less sensitive materials such as wood, leather and oil paintings, should be lit to more than 200 lux. Above this level the eye does not see detail any more accurately. The use of shutters, blinds, shades and tinted UV filtered glass can be used to control the amount of light entering a room and assists to control the temperature and RH within a space. To maintain constant light levels and temperatures, artificial light sources can be used.
However the use of 'yellow' light, such as the ordinary tungsten light bulb, is less damaging than 'blue' or UV lights such as neon tubes. The latter causes the most damage.
Factors which should be monitored when an object is on display or in storage include the maintenance of the building or museum, facilities and equipment/plant, internal environment, pests, suitability of furniture and fittings and containers which hold the object or collection.
Good handling of objects will reduce physical damage to the collection, as our hands have natural oils and acids that eventually affect and damage the objects within the collection. To help control this irreversible damage these precautions should be taken: avoid touching objects (wear gloves); storage and work environments should be organised to encourage good handling; prepare guidelines for the use of the collection. This applies when the object is in storage or on display.
Packing methods may vary depending if you are moving an object or placing it in short or long-term storage. Certain storage material, such as acid-free paper should be used, as these do not release harmful gases. For very precious and delicate objects, it is advisable to call a profes-sional conservator/restorer for assistance.
Labelling reduces the need to handle an object. Each individual object should have its own label if it is to be stored. Labels should be made from acid-free tags and attached to the object using cotton string. No sticky labels should be used as the glue will eventually affect the object.
Housekeeping, along with preventive conservation measures, will help maintain collections in a clean and safe manner. By cleaning the environment and protective dust sheets and taking quarantine measures (for pests), additional steps can be taken to maintain a collection. Following these general rules will assist in the longevity of any object or collection.
ICOM is the international organisation of museums and museum professionals, committed to the conservation, continuation and communication to society of the world's natural and cultural heritage, present and future, tangible and intangible. Museum professionals, NGOs, or private collectors interested in knowing more about ICOM Malta may call 7909 3948 or e-mail heritage_enterprise@onvol.net.
Ms Fabry and Mr Schirò are chairman and vice-chairman of ICOM Malta.