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Executive Summary
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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