It Burns, It Burns!
Cellulose nitrate base film is relatively unstable and escaping toxic gases (nitric oxide, nitrogen dioxide) can attack nearby acetate and polyester base films. It is also highly flamable! DO NOT TAKE THIS LIGHTLY!
Never store any nitrate base materials in sealed containers or without ventilation. Such dead storage increases the rate of decomposition. Pack the reels loosely in ventilated boxes or cabinets, and store them in a room apart from all other photographic materials. Do not let the storage area temperature exceed 70°F (21°C). If you achieve a lower temperature without increasing relative humidity above 45 percent, that s even better. Relative humidity below 40 percent retards decomposition even more, but makes the film more brittle.
Nitrocellulose was used as the first flexible film base, beginning with Eastman Kodak products in 1889. It was used until 1933 for X-ray films and for motion picture film until 1951. It was replaced by safety film with an acetate base. It was discovered decades later that nitrocellulose gradually decomposes, releasing nitric acid which further catalyses the decomposition. Low temperatures can delay these reactions indefinitely. The great majority of films produced during the early twentieth century have been lost forever either through this accelerating, self-catalyzed disintegration or studio warehouse fires.
  Nitrocellulose film base manufactured by Kodak can be identified by the presence of the word Nitrate in dark letters between the perforations. Acetate film manufactured during the era when nitrate films were still in use were marked Safety or Safety Film between the perforations in dark letters. Letters in white or light colors are print-through from the negative. In addition, nitrate stocks had been imprinted with an inked, visible frame line mark that was oriented across the width of the material. Eastman Kodak simply changed this orientation from across the width of the film to perpendicular to the length of the film stock to denote safety based products. However, not all stocks contain this mark. (See Pictures Above)
Color negative film was never manufactured with a nitrate base, nor were 8 mm or 16 mm motion picture film stocks.
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