Preventive Conservation: Agents of Decay
D. Gilroy and I. M. Godfrey
The simplest and most inexpensive way to look after an object or collection is to prevent it suffering deterioration in the first place. Whether an object is in a home or in a museum, the same causes of deterioration apply. A metal artefact in a garden shed will suffer more damage than it would if stored in a box inside a house. Similarly a painting on display in a home or gallery may deteriorate more if placed into a less favourable museum storage environment. There is no point in spending time and materials to treat an object if it is returned to the same conditions which led to the original deterioration.
Information presented in this section concentrates on the environmental factors which cause deterioration in materials. Different climatic zones have their own distinct problems. High humidity in the tropics and salt-laden air in coastal regions are typical examples which should receive extra consideration. Other obvious dangers to collections include fire, flooding and theft. Although these factors must be considered by those responsible for a collection they are not covered in detail in this book.
It is important to know from what materials an object is made and their susceptibility to the various causes of decay. This information is useful in determining where and how it should be stored or displayed.
Thorough preventive conservation practices should be established and regular inspections are essential if the best conditions for a collection are to be maintained. It is important, for example, not to take food or drink into display or storage areas. Spillages have the potential to not only damage objects but also to attract potentially damaging pests. Apart from the obvious health issues, smoking is not recommended in these areas because of the risk of damage from either fire or smoke.
Another important issue is the level of access to artefacts. Materials used daily for educational purposes should be copies or non-essential artefacts because constant handling will cause deterioration through either breakage or general wear and tear.
To reduce the risk of cross contamination in storage and display areas, any new material coming into a collection should be isolated initially, inspected and if necessary, cleaned. Treatment of pests should be arranged if infestations are found.
The most significant environmental factors which contribute to the degradation of objects are listed below:
- relative humidity (RH);
- pollutants; and
- biological pests.
Many of these factors are interrelated and cannot be considered separately. Bright sunlight for example will cause photochemical damage to light-sensitive material, increased temperature and decreased relative humidity.
Each of these agents of deterioration will be discussed in turn in the following sections with guidelines given regarding the types of conditions that will enhance the longevity of materials. As most collections are made up of an assortment of objects and material types no one set of conditions will be suitable for all objects. Where a choice has to be made, conditions should be tailored to minimise damage to the most sensitive of the objects.