Preventive Conservation Overview

Museums have a responsibility to implement preventive conservation measures to prevent further deterioration of collection items. From a preservation viewpoint, it is essential that temperature and relative humidity (RH) in storage and display areas be at a constant level. Temperature, relative humidity, cleanliness and light levels all affect the environmental conditions in storage areas, but can all be controlled fairly simply. As objects are often delicate it is important that handling procedures for moving objects are in place.

How can conditions in display and storage areas be improved?

During the early stages of the museum’s development environmental factors involved in setting up a successful museum need to be considered. Museums have an obligation to care for their collections in a way which will ensure that they remain in the best possible condition, for as long as possible. In order to do this museums must ensure that collections are stored, displayed and transported in secure conditions where the risk of damage and deterioration is minimal at all times. The same care should be taken with collection documentation, both electronic and manual.

The chemical make-up of most materials is such that they are unstable and change with time.  Most museum objects begin to deteriorate from the moment they are made. The rate and degree of deterioration depends on the environmental conditions to which the artefacts are subjected. These environmental factors include:

• Temperature & relative humidity (RH)
• Light and UV
• Pollutants
• Insects and Pests
• Human Influences

See also Preventive Conservation – Environmental and Biological Factors

Deterioration can be caused by any or combinations of these factors whilst objects are in storage, transit or on display. As part of any long range planning it is advisable to conduct an initial environmental survey to build a profile of the current environment in the museum building. This survey would entail monitoring the environmental factors through an initial one-year seasonal cycle and assessing the data to determine factors that require attention. Readings of the outside weather conditions (temperature and RH) should be collected at the same time so that the effectiveness of the building as a buffer (insulation) can be gauged. Monitoring the museum environment should be an ongoing program once the initial survey has been acted on. 

There are some simple strategies available for achieving a stable environment that are sympathetic to heritage buildings, cost effective and reliable. Often the thermal mass of a building creates a stable environment within. Ceiling and wall cavity insulation will improve the stability of the environment as will adequate crawl space venting. As sunlight passes through the windows of the museum, heat is trapped, raising the room temperature (the greenhouse effect). Eliminating direct sunlight by installing blinds and curtains on all windows will help to reduce daily temperature fluctuations that effect RH stability. Planting deciduous plants that shade the north and west facing walls of the museum in summer will minimise the internal temperature increases during the day. In winter these plants drop their leaves and allow the sun to warm the north and west facing walls, preventing the internal temperature from dropping too much. Such plantings should only be considered if they are in keeping with the preservation of the site. As an alternative to plantings, awnings, extended eaves or temporary shade screens can be used. It may be appropriate to ventilate using windows and fans on an as-needs basis to reduce temperature and RH levels. In winter it may be necessary to increase the temperature in the room slightly using a heater with a thermostat on a low setting (although check with the manufacturer if it can be left on for extended periods of time). The slightly higher temperature will lower the humidity.

The more 'housing' an object has around it, the more it will be protected from the elements, ie if an object is in a building, the material of the building will offer protection to the object. If the object is in a display case, or stored in an acid free box, it will be further protected against fluctuating humidity. In some instances it may be more realistic to create individual environments around objects than to try and change the internal environment of a building. Objects can be stored and displayed in cases which contain hygroscopic (water absorbing) materials such as acid free mount board, washed cotton and linen etc, as they will stabilise the RH by absorbing or giving off moisture as required.  It is essential that such cases be well-designed using materials that do not give off harmful gases and condensable vapours. Ideally all objects should be stored in an archival quality box, wrapped in acid free tissue to help buffer against environmental changes. 

Try to avoid placing objects on or against external walls as they can be prone to condensation and west-facing walls can be a source of fluctuating and high temperatures.  More sensitive organic objects should be placed in inner rooms if possible, away from external walls.  Spacers made of ethafoam should be placed behind frames so they are not in direct contact with the wall. This will allow the air to circulate behind the pictures and help prevent the hanging object from being effected by the changes in temperature and humidity conditions of the external walls.

As part of the planning process, a disaster preparedness plan should be developed and implemented to eliminate or reduce potential risks to the collection including: fire and flood, theft and burglary, vandalism and accidental damage. In addition to prevention, a comprehensive recovery plan should be developed that details skills and resources that can be accessed in case of an emergency or disaster.

Further references and reading:

Museums and Galleries NSW, Online Resources

Australian Institute for the Conservation of Cultural Material, ReCollections

Museums Australia Inc (NSW), Museum Methods, A Practical Manual for Managing Small Museums, Sections 4.2 Environmental deterioration; 4.3 Recommended environmental conditions for museum objects; 4.4 Environmental monitoring; 4.5 Light and Lighting; 4.6 Choosing the best display and storage materials and 4.7 Integrated pest management – using insect growth regulators

Bart Ankersmit, Martina Griesser-Stermscheg, Lyndsie Selwyn and Susanne SutherlandBasic care, Recognizing metals and their corrosion products