Volume 19, Number 4
Sep 1995

NARA's 1994 Preservation Conference:
Acetate Film

Reprinted with permission from the September 1994 AIC News, p. 17.

The National Archives and Records Administration ninth annual preservation conference was held on March 15 [1994] in Washington, DC. The topic of this year's conference was "Cellulose Acetate Films: Magnitude and Nature of the Preservation Concerns." Talks focused on arresting the deterioration of the 50- to 75-year-old films now generally acknowledged to be at risk. Speakers included Peter Williamson, Museum of Modern Art (MoMA); James Reilly, Image Permanence Institute (IPI); A. Tulsi Ram, Eastman Kodak; Leslie E. Smith, National Institute of Standards and Technology (formerly National Bureau of Standards); William Lull, Garrison/Lull Environmental Engineers; Betty Hill, NARA; and Steve Puglia, NARA.

After Reilly discussed the chemistry, technology, and history of acetate, as well as the characteristic stages and causes of film deterioration, Williamson talked about the history of deterioration in MoMA's film holdings. The museum founded its film lending library in 1929. During the 1930s many nitrate films were copied onto acetate, which was first noticed to be deteriorating in 1958. At the time, it was assumed that the deterioration was caused by (1) increased demand for the films during World War II (leading to physical abuse of films during worldwide shipping) and (2) inferior film stock available during the war era.

MoMA staff noticed serious acetate-film deterioration in 1977-78 and recommended segregating deteriorated film as well as inspecting of viewing copies. However, by 1980 it appeared that the problem was not limited to frequently lent films. The increase in film-duplication costs resulting from silver speculation in the early 1980s led MoMA to recognize that duplication was more costly than improved storage at lower temperatures, so in 1992, MoMA began building an offsite cool storage facility.

Reilly's research showed that the rate of film deterioration depends on storage conditions and is greatly diminished by lower temperature and relative humidity. IPI has developed temperature and humidity charts that estimate how long it takes for film to reach advanced levels of deterioration.

Ram discussed recent Kodak research in color motion picture film stability. Because deteriorating acetate film releases acid, film acidity increases dramatically in closed film cans. Color dyes are very sensitive to small changes in pH and can decolorize as the pH becomes even 0.5 units more acidic. This sensitivity to acid, along with light and and heat exposure, contributes to color fading. In an effort to control pH, Kodak has experimented with the use of molecular sieves. These small packages of chemical granules, placed in the film cans, absorb excess moisture, acids, and other off-gassing components of deteriorating film. Kodak's experiments with these sieves show improved dye and film stability when motion picture film is stored with precise amounts of the sieves in sealed cans. The sieves are being field-tested worldwide and are now commercially available through FPC (a Kodak Company) at an estimated cost of $2-$5 per can. Contact: FPC, 1017 N. Las Palmas, Ste. 301, Hollywood, CA 90038; 213/468-1574; ask for item #5150.

Smith noted that other cellulose acetate-based materials (audio disks and tapes, laminated documents, and magnetic tapes) also deteriorate. He pointed out that despite the experimental use of molecular sieves, at present the only known safe and cost-effective method for preserving large film holdings is a controlled cool, dry climate.

Lull, in his discussion of storage vault design, explained that engineers with specialized training (rather than mechanical engineers) are required when designing cold temperature vaults that can maintain a stable temperature and low relative humidity. It is also important to use contractors familiar with the requirements of film vaults as opposed to commercial refrigerated rooms found in restaurants. Essential design elements include easy equipment access for servicing, local servicing and preventive maintenance, alarmed environmental monitoring systems, a test run of several months to verify that the vault runs as desired before housing records inside, and the provision ofa three-year maintenance contract by the design/build firm. Lull estimated that building costs should be $200-$350 per cubic foot.

Hill emphasized the complex problems of NARA's millions of film holdings, which often have aged and been subjected to unknown previous storage conditions and processing before entering the collection. She pointed out that duplication and cold storage each have disadvantages as means of preservation. When contracted to outside vendors, duplication can be costly, and it can be difficult to verify that the duplicates meet preservation quality standards. Cold storage prevents fast access to the film by researchers, since the negatives need time to come to room temperature.

Puglia suggested improving storage conditions to buy time for the entire collection and then duplicating records in order of priority. He also discussed a cost-benefit analysis he developed to compare cost of various storage vaults (taking into account capacity, energy costs, and temperature/relative humidity requirements) with duplication (size of holdings, formats, and duplication method were considered).