Principles of cinematography : a handbook of motion picture technology (1953)

72 PRINCIPLES OF CINEMATOGRAPHY Fig. 27. — Rack-and-pin processing unit. One of the most simple methods of processing short lengths of motion picture film is shown in Figure 27. Short vertical pillars are arranged on a horizontal board so that the film may be wound on edge in a roughly spiral fashion. The loaded former is placed first in the developing bath which must, of course, be a shallow tray large enough to permit the operator to handle the former with ease, then into the fixing bath and, finally, into a tray through which a constant flow of water is passing. To dry the film after processing it may be placed in a current of warm dust free air whilst still mounted on the former, or may be rewound onto a drum in spiral fashion, as shown in Figure 28. This simple arrangement can only be used when very short lengths of film are to be processed, usually not longer that 50-ft (15-24 metres), and, even under these conditions, loading such a rack is quite a tedious business. To overcome this a rack has recently been designed in which the vertical pillars are mounted on hinges so that all but the central four pillars may be folded away from the film loading path and raised individually as each is required. The hinges are arranged to fold outwards so that loading the film will always tend to hold the pillars upright. Since film base dimensions vary with the prevailing humidity, it is necessary to provide means whereby the overal length of the Fig. 28. — Film drying drum.