A disaster can occur to an audiovisual materials collection as a result of long-term or short-term factors.
Short-term factors involve the more commonly thought of disasters such as flood, fire and severe damage or destruction of the storage vaults.
Long-term factors can include extended periods of storage where:
- the relative humidity is high, especially when it is greater than 60 per cent
- storage temperatures are constantly or frequently high or fluctuate over a short period
- vermin are uncontrolled
- high levels of oxidising agents or other pollutants are found.
Disaster planning should be a very high priority and plans need to be reviewed on a regular basis. Creating a list of disaster planning questions that cover likely disaster scenarios is an important first step in planning or planning review.
Equipment and external services required for recovery should be checked and updated similarly. Staff should be familiar with the elements of the plan, especially their own areas of responsibility.
Prevention practices and planning
Some aspects of good collection management practices such as correct wind tension, clearly identifying marks on both the film can and film, and condition reports are important elements of disaster planning. Correct wind tension can prevent or reduce the impact of some disasters and clear identification marks will enable accurate notes to be included in condition reports. Any unanticipated changes in the condition of the film in the future can be cross checked against other films that have suffered the same disaster and treatment, possibly avoiding a further collection crisis.
An essential factor of any disaster recovery is the ability to rapidly house the collection in a safe and stabilising environment as soon as the disaster has been noted. In film collections this invariably means cool or cold, dry conditions. An important first stage of disaster planning is identifying local cool-store or cold-store facilities that may be used at short notice. Food suppliers and shipping agents are often a good starting point for this.
Other components of a disaster recovery plan should include:
- identify high priority sections of the collection
- staff organised into teams to handle each stage of a disaster recovery
- equipment and training needs to be provided and procedures continually refined
- organisations or companies that offer products or services that are required for disaster recovery should be listed and the list should be frequently revised.
Where significant water damage is suspected, as in floodwater or fire supression, films need to be stored in very cool conditions to reduce the likelihood of mould growth or bacterial action. Rapid air drying of wet film can create significant problems with the gelatin emulsion strongly adhering to adjacent layers in the film pack. This is known as 'blocking’.
Where fire hoses have been used there may be the need to match films with cans as the hose pressure may have blown cans from shelves.
Water damage recovery
The first recovery actions should involve a rinse with clean, preferably deionised or distilled water, to remove any surface debris and then placing in temporary storage under very cool or cold conditions until conservation treatments can be arranged.
Time is critical. Biological and chemical reactions are only slowed down by cold conditions, not stopped!
The sooner conservation treatments can start, the lower the risk of more serious damage.
Films should not be unwound for examination at this stage. If the film had high free acid levels, as may be encountered in decomposing films, then the gelatin emulsion will be very unstable and suffer significant damage by unwinding.
Where extended storage under high relative humidity has occurred, the films should not be immediately unwound as the gelatin may have blocked.
To identify the extent of the effect of the disaster a program of careful unwinding and examination needs to be instigated, possibly working on a statistically determined sample from each storage location. The program must incorporate training of staff in film handling and especially the problems of blocking and the degree of damage that can occur by incautious examination.
In the desire to quickly establish a remediation plan staff concerns such as OH&S issues of extended periods of film winding, with the possibility of Occupational Overuse Syndrome, and suitably designed and equipped work spaces must be considered.
Water damaged films where the gelatin is still stable will most probably require some form of rewash treatment to rinse any pollutants from the gelatin and film base. Before a rewash can be performed some films may require an unblocking treatment to gently release the adhesion between the film layers. This is a specialised treatment that often requires long periods of time with regular attention to the films to prevent further damage.
After rewashing, which is an aqueous process, a solvent cleaning may also be required to remove any oils or greases that have been carried onto the film during the disaster.
Fire poses the obvious problem of charring of the film itself, but there are several other issues that can arise:
- melting or fusing of a plastic reel, film can or can coating onto the film
- large dimensional changes in the film base or distortion of the film base
- fading or loss of the image, especially colour dye images
- blocking of the gelatin emulsion by melting.
It is often the case that only one part of the film is affected when there is a fire. This could be in part due to the low specific heat of film base materials, so only the area directly touched by fire is significantly affected. However, due to the way in which film is stored and transported through equipment, this can have a devastating effect on the film. If one part of the reel has been damaged then this will appear as a cyclic blemish, or regular loss of content when a film is projected or duplicated.
Fire damage recovery
The first stage of recovery from fire is identifying the film and assessing any obvious physical damage or soiling. Loose soils can be vacuumed away and melted plastics or coatings can usually be carefully removed — often there is little in the way of adhesion. The film should be recanned if necessary with all identification marks transferred to the new can.
When the film is examined, extreme care is required as the film may be blocked or very brittle, especially the emulsion. Assess the first few layers or wraps of the film reel for any dimensional changes or distortion. Any changes will be most apparent in the outer layers.
Some success has been had with unblocking fire damaged films. This, however, is a high risk operation and should only be undertaken if there are no alternatives.
Before extensive repair work is commenced, check the holdings of the collection for duplicate films as it may be more cost effective to change the collection status of the duplicate film or even obtain a copy from another institution.
If no other options are available then the film can be spliced together, removing the damaged sections.
Severe damage or destruction of the storage vaults
In the event of an earthquake or other event that seriously damages the storage structure and dislodges films the first response, once the site is safe for staff return to, is to identify films and return them to their respective cans or recan them if the former is not possible. Debris can be vacuumed away at this stage.
Physical damage needs to be assessed. If the films are not affected by water or fire they can be carefully unwound for examination. Film wound in a pack is relatively tough and any physical damage is likely to be restricted to the edges of the pack or the reel or core. Therefore basic repair techniques should be able to restore the film to a fully useable condition.
A solvent clean before returning to storage is advisable, but not necessarily essential. The decision needs to be made on the type of conditions the film was exposed to and whether the cans remained intact.
Storage plant failure
In the event of plant failure in the storage vault all access to the store should be suspended. This will slow the rate at which the temperature inside the vault will rise and help reduce the inflow of water vapour.
If the plant cannot be repaired quickly or if the fault occurs at a time when staff are not around to monitor the failure or there are delays in arranging repairs, 'time out of storage’ should be noted in condition reports. Remote sensing of the conditions inside the vault is highly desirable. If the conditions exceed preset safety levels then arrangements to relocate the collection to temporary storage should be made.
The effect of the long-term issues listed can be controlled by regular inspection, testing and datalogging of environmental conditions of the storage facilities. Correct preparation of films before entering long-term storage, i.e. correct wind tension, can material and no foreign matter inside the film can, will further ensure a reduction in the risk.
Good environmental hygiene and pest management to reduce vermin around vaults are also important. Pest management does not necessarily mean chemical fumigation, but rather preventing vermin becoming established through measures such as:
- clearing away vegetation and rubbish from around buildings
- sealing potential entry points around the roof or service areas
- regularly cleaning and removing rubbish from the vaults themselves.