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Executive Summary

Cellulose acetate is a transparent plastic material that has been used as a carrier for photographic negatives, motion picture film, microfilm, microfiche and sound recordings. Cellulose acetate is susceptible to deterioration over time through a process termed the ‘vinegar syndrome’, which initially involves the release of acetic acid. Low temperature/low relative humidity storage and removal of any generated acetic acid are known to slow this degradation.

Lowering the temperature lowers the rate of chemical deterioration reactions. Cold storage (-18° C) is recommended for permanent storage of materials that are already deteriorated. However, cool storage (0° C – 16° C) will also significantly slow the chemical reaction.

Care should be taken to avoid fluctuations in both temperature and relative humidity of storage conditions. Materials in cold storage may need up to a week equilibrate to ambient conditions to prevent the possibility of damage during warm-up.

Since deacetylation of cellulose acetate requires the presence of water, the reaction can be slowed by limiting the amount of moisture present in the film base. However, acetate film is known to become brittle below 20% RH so storage at relative humidities of 20% - 50% is recommended.

The use of enclosures can be important in controlling the microenvironment of cellulose acetate film. The type of enclosures used will differ depending on whether the storage environment is humidity controlled.

Removal of acetic acid produced by the deterioration of cellulose acetate will reduce its catalytic effect and slow further deterioration.

Facilities that can be used to store large collections of cellulose acetate materials include humidity controlled cool and cold storage vaults. Options for smaller collections include domestic frost-free refrigerators and freezers. Protection from high humidity levels is essential even in cold storage.

Geographical location has an influence on the storage environment where temperature and/or humidity are not controlled. Air conditioning without humidity control can increase the internal relative humidity to levels higher than those outside on hot days.

Systematic monitoring of collections is an essential element in managing cellulose acetate collections.

Copying methods such as duplication and digitisation are often used as preservation strategies in association with the provision of cool or cold storage. Factors such as the format of the material, whether or not originals are to be retained, and whether duplicate or digital copies are required for access purposes, have an important bearing on the preservation management strategy adopted.

Information about existing cold stores in Australia is provided in Appendix 1 of this report. It is intended that this information will be useful in facilitating cooperative cold storage arrangements.

In implementing any storage strategy, OH&S guidelines need to be followed.

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