a metal cupboard for storing reels of film. In order to prevent the film’s physical and mechanical properties from deteriorating during long-term storage, the interior of a film safe is thermally insulated from the outside and a constant humidity level (65–80 percent) and chemical regime are maintained inside. The walls and compartments of the film safe are lined with a layer of thermal insulation, the doors are sealed with a rubber gasket, and an uncovered dish filled with hygrostat fluid (with a typical composition of 15 parts acetone, 25 parts glycerol, and 60 parts water) is placed inside the safe. The evaporating liquid passes through special openings in the compartments, humidifies the film, preserves and restores the film’s elasticity, and prevents shrinkage. The film must not be wound tightly on the reel, or the vapors from the hygrostat liquid will not penetrate to all parts of the film.
A portable film safe is a metal box with a double bottom. Between the two bottoms is a packing of Porolon or felt soaked with hygrostat liquid; vapor from the liquid penetrates the main interior of the case through a mesh partition.
E. A. IOFIS