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As photographic film has become an important documentary material, a systematic study of it was undertaken by the National Bureau of Standards as a part of its general research on problems relating to the preservation of records. This summary was prepared in order to have the more important information developed available in one publication. The films tested are of two types, one coated with a photographic emulsion and the other having a light-sensitive dye incorporated in the base for forming the image. The sheetings comprising the bases are, for the first type, nitrate and acetate, and for the second, viscose and acetate. The stability of the films was determined by heating them at 100° C for various periods and testing them for decrease in folding endurance, weight, and viscosity of solutions, and for increase in acidity. The acetate and viscose bases were also tested for increase in copper number under the heat test. Both types of acetate film tested were very stable and are considered suitable for permanent records. The nitrate film is of little value for record purposes because of its inflammability and instability. The viscose film was in an intermediate position and appears to be suitable for records requiring moderate longevity. The images of the acetate and viscose films were not affected appreciably by the heat treatment. The emulsion type of film was also tested for presence of sodium thiosulfate, and that having an acetate base was in addition tested for presence of nitrate. To aid in the selection of acetate film for permanent records, values are given for the strength, stability, and chemical purity considered desirable. Apparently the combined effect of the light and temperature to which film is exposed in projectors designed for documentary use is not a serious consideration. Relative to possible fading of photographic images when exposed to light, those contained in emulsion are known to be very stable if properly made, and exposures of both the acetate and viscose Ozaphane film indicated that images in such film are likewise very resistant to fading if the proper dyes are used. As acetate film becomes brittle when dry, it is recommended that it be stored at a relative humidity of about 50 percent. The special precautions required for storage of nitrate film because of its inflammability are described. The results of investigation of the size of the pressure-relief vents necessary to prevent, in case of fire, explosion of vaults containing nitrate film indicate that vents larger than those previously recommended may be desirable. Micromethods for finding the chemical condition of record-bearing films without affecting their serviceability were developed. To minimize the damage to film records through scratching and handling, it is recommended that they be cleaned with carbon tetrachloride and handled with clean white cotton gloves. A list of the more detailed published reports of this work, together with those dealing with paper as a record material is given.

Summary report of research at the National Bureau of Standards on the stability and preservation of records on photographic film/