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Beginning in the early 1970s curators, librarians, and archivists in charge of collections containing historical photographic negatives began to notice that certain portions of their collections were beginning to display serious deterioration. The damage observed typically included badly distorted negatives showing severe shrinkage. Also, because of the base shrinkage, the various layers of the film laminate were becoming separated, making the negative unprintable. The smell of acetic acid accompanied this phenomenon.

Because these negatives had been manufactured relatively recently, it was obvious that these negatives were not on cellulose nitrate base and that they were in fact "safety" negatives. At this point in the discovery of the problem, most of the affected negatives seemed to date from the late 1940s and early 1950s. Some of the early evaluations of the problem considered these negatives to be isolated examples of degraded cellulose diacetate film base which had become unstable due to extreme temperature and humidity conditions.

Since that time, more historical negative files have found their way into various repositories. Many of these collections suffer similar problems and the total number of degraded negatives is increasing. The once small "pockets" of degraded negatives are getting larger, and the dates of origin are no longer limited to a few years. Many collections with safety negatives dating from 1925‑1955 are finding these problems in their files.

To make matters worse, very little information about these negatives is available to these caretakers in the literature with which they are familiar. What little mention there is in curatorial or preservation sources is essentially accurate in that it stresses the need for the isolation and duplication of what have been called "diacetate negatives." But these sources lack consistency in terminology, a reasonable explanation of the problem, or a true idea of its scope. Much of this information is simply not available. The film manufacturers, who genuinely had not been aware that the situation had become so widespread, responded that the problem is chemical degradation of the film base due, primarily, to improper storage. Although accurate, this seems to place the blame on mismanagement by the repositories themselves.

At the same time, exaggerated stories about the situation are being traded between anxious curators and a folklore about these negatives is beginning to emerge. It is the purpose of this project to begin the process of defining the problem in such a way that a firm groundwork will be laid for future work. While much of the tone of this report and its recommendations will be directed towards those who work directly with these collections, it is hoped that it will be also useful for those who will continue the technical work that still needs to be done to more fully understand the problem. This report combines a distillation of the existing technical knowledge and practical observation. It represents a very conscious effort to state accurately what we know, what we do not know, and what we can reasonably do about the present situation.


This project was funded by the University of Louisville and the National Museum Act.