The Bioscope (Jul-Sep 1931)

August 12, 1931 MODERN CINEMA TECHNIQUE THE BIOSCOPE iii Storing Valuable Ventilation Problems with Films Communication No. 447 from the , II Kodak Research Laboratories. ( Read before the Society at Washington) || Sectional Waterproof Cabinets To date, most film storage vaults have been designed merely with a view to protection of the surroundings in the event of a fire within the vault. This paper gives an account of experiments made with various storage cabinets which have been designed so as to afford more protection to individual rolls of valuable film without increasing the risk to surrounding property. At the outset it was considered that the following conditions should be fulfilled — (1) In addition to being immune to external fires, the vault should be so constructed that in the event of an internal fire only a minimum quantity of film would be destroyed, and that a minimum fire menace to the surroundings would be incurred. (2) Each roll of film should be contained in a separate compartment and insulated so that one roll could be burned completely without setting fire to anything else. Also, the different compartments should be vented in such a way that gases, soot, etc., from one burning roll would not reach any other roll. Damage from Water and Mechanical Strain (3) The film should be shielded from water coming from any source. The most probable sources of water would be : (a) An automatic sprinkler discharge during a fire, (b) accidental discharge of a sprinkler, (c) ceiling or pipe leaks, and (d) water on floor from leaks, sprinklers and similar sources. (4) The method of storage should insure that the film is not subject to mechanical injury. If wound on too small a core the film will be curled excessively, while if a large roll is stored on edge the circular shape of the roll will be distorted. Negative film should be wound on as large a core as is practical and should rest on its fiat side. Greater freedom from curl is insured if the film is stored in large rolls. Avoid Metal Spools It is customary to store motion picture positive film on metal reels placed on edge. For long time storage this is not desirable, because ordinary iron reels are apt to rust and the rust particles offset on to the film on rewinding. (5) The film roll size should usually be limited to 1,050 ft., unless the smallest handling unit is larger. A larger roll would mean unnecessary loss in case of fire. The rolls should be wrapped in paper or preferably in a sealed envelope, which would not deteriorate rapidly in contact with the film. The wrapped roll should be placed in a round •container made preferably of fibre, wood, or other non-heat-conducting material which will not be damaged by nitrogen oxides. The container should have a loosely fitting cover and should not warp. (6) The storage compartment should be capable of being built up in units as required. (7) The vault should be capable of being cooled to a temperature of 40 to 45 deg. Fahr., which temperature is considered sufficiently low to prevent appreciable decomposition of the film base with time. (8) The vault should preferably be as immune as possible to earthquakes, vandalism or destruction in time of war, but in this respect protection can be insured by making duplicate copies and storing these in places widely separated geographically. Sectional Cabinet Principle After discussing the drawbacks of existing methods of storage, the report states that the Geyer Film Laboratory has designed and installed a series of cabinets made of wood or asbestos board on the principle of a sectional filing cabinet. The front ends of the drawers are covered by means of a large door and the rear ends open into a common flue which permits the escape of any combustion fumes. Each film roll (1,000 ft.) is placed inside a wooden box fitted with a telescoping wooden cover. Best to Let It Burn At the outset it was considered that a cabinet built on the Geyer principle would be most suitable for the purpose intended, because this would not depend on the use of water, which often causes more damage than the fire itself. When a roll of film once catches fire it is impossible to save it even if it is quenched in water, because the convolutions are then apt to stick together. It was therefore considered preferable to allow the roll to burn up completely, providing the adjacent rolls are protected from the heat and fumes resulting from the film combustion. Nature of Storage Cabinets Tested. — A number of experimental cabinets designed on the filing cabinet principle were tested by igniting bare rolls of nitrate film in one compartment, while the remainder contained film both in the bare condition and enclosed in metal cans. The first test cabinet of f in. pine consisted essentially of several shelves separated sufficiently to allow the cover of the film can to be raised, to permit the free escape of gases. The rear opening of each compartment was closed by a flap, while the front was covered by a single large door which could be closed tightly against an asbestos gasket. The design of a second wooden cabinet tested was similar to the above, but this was covered completely with sheet metal. A series of holes were drilled through the metal at the ends of the shelves and uprights to provide vents for distillation products from the heated wood. Fibre rails, J in. high and J in. wide, were fastened to each shelf so as to create an air space between the film and the shelf. The sheet-metal awnings or guards fitted at the lower edge of each shelf at the rear of the cabinet served to deflect the flames from the burning film into the flue and prevent their access to the upper compartments. Fire tests with the above cabinets indicated that the sheet-metal covered cabinet adequately protected all other rolls when one was ignited, while in the case of the plain wooden cabinet the wood ignited while the first roll was being consumed and the remaining rolls eventually caught fire. Fireproofing Paint Ineffectual A fireproofing paint was applied to one of the plain wooden cabinets, but this did not give any apparent protection from fire, the cabinet being completely consumed. In view of the great expense involved in covering the wood with sheet-metal, a cheaper cabinet was constructed consisting of a plain wooden cabinet fitted with sheetmetal drawers ; open only at the end toward the flue, thus eliminating the necessity for a gasket-tight drawer, while at the back the sheet-metal drawers extended beyond the cabinet into the flue spaces and were closed individually by weighted sheet-metal flaps. This type of cabinet proved satisfactory, and it was possible for a roll of film in one compartment to be completely consumed by fire while the remaining rolls were unaffected by heat or fumes, although the woodwork abutting the rear flue was somewhat scorched. Results of Further Tests At this point it was decided to make further tests with a storage cabinet of practically useful size with the sheet-metal drawer and a capacity of forty 1,000 ft. rolls of 35 mm. film. This cabinet was tested by causing three 1,000 ft. rolls of 35 mm. positive motion picture film contained in three drawers to decompose simultaneously by the application of heat. When these rolls had decomposed completely, other rolls of film which had been placed in drawers adjacent to those where decomposition took place and at other points were examined. The protection afforded from heat and fumes was entirely satisfactory. Even cans in drawers adjacent to those where the heat was evolved were not sensibly 1 A NOTION OF LIGHT AN OCEAN OF LIGHT I CARBONS