Top of page

Program National Film Preservation Board

Film Storage White Paper

Keeping Cool and Dry: A New Emphasis in Film Preservation. Redefining Preservation Task Force: Supporting Document A

(published August 1994)

Just as film itself has a history, so does film preservation. Today the National Film Preservation Board is suggesting that our national preservation policy change to reflect new technical knowledge about film decay. Research shows that film needs better storage to survive, and that film in all stages of decay can have a longer useful life with small improvements to its environment.

Our new policy should broaden the definition of preservation beyond its traditional meaning of copying old film stocks to newer ones. It should view preservation as a whole film enterprise, integrating previously separate issues of storage, access, and selective restoration into a coherent, cost-effective approach. The other purpose of whole film preservation is to develop a balanced use of resources to save films in all formats and types in large archives and small collections.

Film long ago ceased to be only for the movie theater; as film technology became simpler and more accessible, it entered many arenas of education, industry, documentation, and personal expression. Our challenge now is to appreciate the fullness of film's variety, to locate and consolidate important fiction and nonfiction films, and to prevent their further decay. The reward will be more films for ourselves and future generations to study and enjoy.

The New Film Preservation Challenge

Current realities in film preservation have been shaped by the history of film itself. From the 1890s to 1950 most professional cinema films (35mm format) were made on cellulose nitrate plastic supports. Nitrate base film can become chemically unstable, and many films that were stored in unfavorable conditions deteriorated beyond use before they could be copied. The focus of preservation activities came to be a systematic program of nitrate duplication as a preemptive measure, before deterioration occurred. The goal of copying all nitrate was a rallying point for preservation, and in some collections it was attained. Nationwide, however, the rising costs of duplication soon outstripped available resources, and it became clear that the scale of the nitrate problem was far too large to deal with in that way.

When manufacture of nitrate film ended, two far-reaching innovations in film technology occurred almost simultaneously. One was the replacement of nitrate with nonflammable cellulose acetate plastic film support. Based on the (now obsolete) accelerated aging tests of the day, film manufacturers announced that safety films had far superior permanence over nitrate films. Attitudes toward preservation were shaped by the conviction that acetate stock was permanent, while nitrate was not. We now know that acetate and nitrate both share a tendency to degrade; in fact, in some collections, the losses from acetate decomposition are greater than from nitrate. Nature does not distinguish much between cellulose nitrate and cellulose acetate when it comes to deterioration.

The second key innovation of the early 1950s was the introduction of chromogenic color motion picture stocks, to replace the cumbersome Technicolor process of the 1930s and 1940s. Audiences and cinematographers embraced color with thoroughgoing and deep affection, so that few films after 1960 were made in black and white. Unfortunately, the use of color introduced a tremendous new problem of rapid color fading. The instability of organic color dyes, like the decomposition of nitrate and acetate film base, results from a chemical process which can be speeded up or slowed by the temperature and humidity of the storage environment. Warm-and-humid conditions accelerate the rates of fading and decomposition, while cool-and-dry conditions greatly slow the reactions.

The focus on nitrate and on duplication that has dominated film preservation efforts does not confront the current realities of unstable safety stock and color dyes. A rising tide of deterioration is flowing through film collections, touching the smaller and medium-sized institutions most acutely. The short life expectancies which once were thought to be only a problem for nitrate now face nearly all films, because almost every film is either on nitrate or acetate base, or else is in color. Today's color is more stable than earlier emulsions, but it still has a short life in archival terms, unless it is stored properly.

Prevention Should Be New Preservation Policy Emphasis

The starting point for policy change is to recognize a number of unpleasant facts. One is the sheer size of the task. There are enormous quantities of films in established film archives, and perhaps even larger amounts in other kinds of collections and institutions. The huge volumes of film mean that massive efforts would be required to address the problem through preemptive copying. Film archives face shrinking budgets for preservation. Resources are diminished not only by rising duplication costs, but also by greater demands that films be accessible. Some collections have no funds at all for preservation copying.

The goal in film preservation is to extend the useful life of collection materials so that they remain accessible to future generations. The probem is to maximize each preservation dollar. Moreover, it is often not enough just to understand how to improve the care of collections; the benefits of preservation actions taken now must be communicated to funding agencies and somehow quantified in order to lay claim to scarce resources. This has been a source of great difficulty for film archives because so much of their work is preventive, rather than remedial, in nature. The benefits of such work are difficult to quantify in terms of dollars-and- cents or years of extended life.

Take an analogy from health care: Preventive medicine (regular checkups, immunization, etc.) is very cost effective, because when conditions are diagnosed early they are less costly to treat and involve fewer complications. Still, there remains a reluctance to endorse a new preventive medicine emphasis because the traditional late treatment pattern is already so expensive. Only with thoughtful analysis and a long-term view does the value of prevention become clear.

The film preservation equivalent of preventive medicine is the collection storage environment. Making original films last longer will reduce the need for emergency duplication and will buy time for collections. In the future, film will be reproduced and distributed by a host of new technologies, some now available and some as yet undreamed of. The key to access in the future is to preserve the original long enough to be converted, restored, and distributed in these new ways. Original films have the maximum image and sound quality, and will be the best platform from which to create access copies in the future. Digital restoration techniques will be a part of, but not a substitute for, preservation of original film materials.

The major preservation problems which now occupy so much of our efforts - degrading nitrate and acetate film base, color dye fading, audio and video tape deterioration are all heavily dependent upon storage temperature and relative humidity (RH). Both science and actual experience agree that temperature and RH are the primary rate-controlling factors in such deterioration. Every treatise on preservation and conservation advises that cooler and (within limits) drier conditions are better for film.

Putting Research into Practice

With color fading and acetate degradation becoming all too evident in film collections, research has turned to investigating these problems. The Image Permanence Institute,(Footnotes 1 and 2) Eastman Kodak Company (Footnote 3), and other laboratories around the world have provided a fuller picture of deterioration behavior. Although the role of temperature and moisture in governing the rate of decay has been acknowledged in preservation science and practice for many decades, something profound has only recently been brought to light: the actual quantitative relationships involved.

Over the last twenty years and especially within the last five a great deal of laboratory work has been done to establish predictive models of deterioration for dye fading (Footnote 4) and film base decomposition in nitrate and acetate.(Footnote 5) These models have shown just how long inherently unstable materials can last under the right storage conditions. They also show the converse that the wrong environment can doom collections to very short lifetimes. Deterioration is always proceeding, sometimes faster, sometimes slower. It is now possible to know, at least in a general way, how long it is reasonable to expect collections to last in any plausible combination of temperature and RH conditions.

Helping Original Films To Last Longer

Recent advances in our understanding of film deterioration point the way to a balanced and cost-effective strategy of improved storage and selective copying. Research shows that even degraded film will last longer under cooler and drier conditions. If film is stored properly from the beginning, life expectancies measured in centuries are possible. A number of major film companies have installed low-temperature storage vaults to protect their valuable film assets. The heart of the new preservation approach is to understand and exploit the relationship between storage conditions and film decay to the advantage, rather than the detriment, of film collections.

Clearly it is time to broaden the scope of film preservation activities and abandon a narrow focus where copying in anticipation of future decay claims such a large share of funding and staff resources. Duplication and physical restoration of films is a vital part of preservation. It should continue, but as part of a balanced program that emphasizes prevention of decay through improved storage. Duplication should be used selectively in cases where films are showing signs of active deterioration, or where physical restoration is needed to make films accessible.

The advantages of such a balanced whole film approach are lower costs and greater useful life for all the films in collections. The costs of improved storage can be considerable, but they are still far lower than any other preservation option. Cold-storage vaults and major environmental control projects conjure up an image of outrageous cost, but when a single feature-length film can cost $40,000 to copy, prevention seems by far the better bargain. While major vault construction is costly, it is also cost-effective for many large collections when the value of the collection and the costs of duplication are considered. For smaller collections, centralized, shared storage in large vaults is a viable way to achieve long film lifetimes.

The new research in film deterioration shows that small, incremental changes in storage conditions can result in considerable life extension for film collections. Staff education and new approaches to environmental monitoring can help collections with few resources to determine where such low-cost but still potent improvements would be possible. In fact, much can be done to preserve films short of large capital projects. The first steps are to understand how deterioration is affected by temperature and RH, and to measure actual conditions. Considerable improvements can then be made by small, simple steps such as lowering thermostats, shutting off heat vents, relocating collection materials within a structure, etc. For some small collections, household freezers can be a very successful storage approach.

Because managers of film collections have become accustomed to thinking that only grand projects and ideal conditions will make a difference, they have lacked the incentives to make incremental improvements. There is a need for better tools with which to evaluate storage environments in light of the new understanding of deterioration behavior. Such tools might include simple electronic monitors that sense temperature and RH and read out in film life, as well as computerized analysis of environmental data that sums up a long period of temperature and humidity readings into a single life-expectancy value. There is also a need for improved techniques for monitoring the condition of films over time so that archives can duplicate films or take other preservation measures when necessary.


Film must be managed like any other valuable, but finite, national resource. We can no longer afford to have a narrow focus in film preservation, concentrating on just one approach or one type of film. A new preservation policy must emphasize education, prevention of decay, and closer integration with outreach activities that make film accessible to a wider audience. This requires an educational initiative to teach the theory and practice of preventive care, and new tools with which to monitor and assess storage conditions. It will involve reexamination of both the funding structures and the practices of film preservation, but it will result in more films being available to us and to future generations.


  1. P. Z. Adelstein, J. M. Reilly, D. W. Nishimura, and C. J. Erbland, "Stability of Cellulose Ester Base Photographic Film: Part I Laboratory Testing Procedures," Journal of Society of Motion Picture and Television Engineers, 101, 5:336-346, May 1992.
  2. P. Z. Adelstein, J. M. Reilly, D. W. Nishimura, and C. J. Erbland, "Stability of Cellulose Ester Base Photographic Film: Part II Practical Storage Considerations," Journal of Society of Motion Picture and Television Engineers, 101, 5:347-353, May 1992.
  3. A. Tulsi Ram, David F. Kopperl, Richard C. Sehlin, Stephanie Masaryk-Morris, James L. Vincent, and Paige Miller, "The Effects and Prevention of the Vinegar Syndrome," presentation at the IS&T 46th Annual Conference, Boston, MA (May, 1993).
  4. Conservation of Photographs, Kodak Publication No. F-40 (Rochester, Eastman Kodak Company, 1985).
  5. James M. Reilly, The IPI Storage Guide for Acetate Film (Rochester, NY: Image Permanence Institute, 1993).

-- Drafted by James Reilly (Image Permanence Institute), in collaboration with the other members of the Redefining Preservation Task Force: Allen Daviau (American Society of Cinematographers), Peter Gardiner (Warner Bros.), Stephen Gong (Pacific Film Archive), Robert Heiber (Chace Productions), and William Murphy (National Archives and Records Administration).