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Quality Control in the Manufacture of Raw Film
By F. WING
Agfa-Ansco Corporation, Binghamton, New York
T is doubtful if any other material is manufactured on a commercial scale under difficulties so numerous and diversified as those encountered in the routine production of highly sensitive photographic film, for here the most delicate chemical reactions and exact physical standards must be maintained with predetermined limits throughout large scale manufacture. There are, of course, many products of the chemist and the maker of biological and pharmaceutical drugs, which are most difficult to prepare, but it must be realized that these products are usually made in small batches, command high prices because of their purity, and can be prepared and purified under the visual observation of the chemist during the process of manufacture.
The film manufacturer, on the other hand, is handicapped because all production operations following the initial steps must be conducted in very subdued light or total darkness, and the little which can be seen during manufacture is useful only in judging physical characteristics of the product, while the all important photographic qualities of film must be determined by actual photographic tests. With these difficulties in mind, one might suppose that the maker of film could rely upon standard testing methods similar to those used in making innumerable other products, where it is common procedure to subject a small sample to specified tests for chemical and physical characteristics with confidence that the result will accurately represent the qualities of remaining material.
Difficulty of Testing Raw Film
Testing methods of this kind have naturally been applied to controlling the manufacture of photographic film wherever possible, and such tests insure uniformity in the constitution of raw materials, emulsions and film base, but the qualities of finished photographic materials are profoundly influenced by variation in physical dimensions, therefore, the testing of representative samples at various stages of manufacture must be supplemented by other tests specially devised to reveal the existence and location in a coating of any possible deviation from established standards.
The average user of photographic film has little or no idea of the methods used in modern large scale production of sensitive materials, and is therefore unlikely to have knowledge of testing methods used to control production. The following description of film testing during manufacture should therefore be of interest to the practical photographer, the cinematographer and the film producer, all of whom directly or indirectly depend upon the efficiency of testing methods to insure quality in their pictures and to minimize production costs.
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