Cinematographic annual : 1930 (1930)

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MATERIALS FOR CONSTRUCTION OF MOTION PICTURE PROCESSING APPARATUS J. /. Crabtree, G. E. Matthews and J. F. Ross* WHEN selecting a material for the construction of processing apparatus, several factors should be considered, namely: (1) The resistivity of the material to the most corrosive liquid with which it will come in contact. For example, a galvanized tank, while fairly satisfactory for washing purposes, is very rapidly corroded by fixing baths. (2) The effect of the material on the photographic properties of the solution. For instance, a developer solution in a brass tank may appear visibly unchanged, but on testing, it may fog emulsions badly, due to the presence of copper salts dissolved from the brass. (3) The time during which the solution will be in contact with the material. If a developer is stored in a japanned tank, the japan will ultimately soften and peel off. (4) The cost of the material. (5) The adaptability of the material for construction purposes. Glass, for example, is entirely unsuitable for large tanks because of its fragility, and the difficulty of annealing such tanks. There are three general classes of materials suitable for the construction of processing apparatus; metallic materials, coated metals, and non-metallic materials. These may be sub-classified as follows: A. Metallic materials: Unplated and plated metals; alloys. B. Coated metals: Enameled steel, asphalt-coated metals, and lacquered metals. C. Non-metallic materials: Enameled steel, glass, impregnated fibrous materials, wood, paraffined wood, porcelain and glazed earthenware, rubber, rubber composition, and nitro-cellulose materials, slate and Alberene stone. Metallic Materials No metal or alloy has yet been found which will resist corrosion in all photographic solutions, and it is therefore necessary to restrict their use to specific purposes. Metallic materials possess certain very desirable properties, however, such as ductility, non-fragility, and general workability. In considering the suitability of a particular metal for construction purposes, it is very important to know whether the article will be built of a single metal or of two or more metals. In the former case, only the corrosive effect of the solution itself need be considered, whereas in the latter case, an electrical current flows between the * Kodak Research Laboratories, Rochester, N. Y. [139]