Journal of the Society of Motion Picture Engineers (1930-1949)

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238 J. M. CALHOUN Vol 43, No. 4 diffuses into the base, which may even continue to swell slightly. This retards the drying of the base. The rate of drying of the emulsion is greater than that of the base, because moisture diffuses more easily from the interior to the surface in the case of the former. Therefore, in spite of the larger quantity of moisture originally present, the emulsion will generally dry sooner than the base. Once the emulsion is sensibly dry it will condition more rapidly than the base to the relative humidity of the drying air. Some of the diffi TABLE 2 The Approximate Moisture Content of Various 'Eastman Nitrate Motion Picture Films in the Drying Cabinet of a Processing Machine Time to Sensible Moisture Content Moisture Content Type Dryness, After Squeegee When Reeled Film No. min per cent gm per ft per cent gm per ft Background X Panchromatic Negative 1230 18.2 29.0 0.96 3.34 0.069 Plus X Panchromatic Negative 1231 20.9 33.0 1.00 3.44 0.070 Super XX Panchromatic Negative 1232 25.6 33.0 1.14 3.66 0.088 Fine-Grain Panchromatic Duplicating Negative 1203 9.5 16.8 0.45 2.58 0.058 Release Positive 1301 8.1 17.3 0.47 2.68 0.061 Fine-Grain Release Positive 1302 5.4 12.2 0.31 2.76 0.064 Fine-Grain Duplicating Positive 1365 5.4 11.0 0.27 2.34 0.057 Temperature of wash water, 68 F. Squeegee nozzle pressure, 30 Ib per in.2 Drying air, 70 F, 55 per cent RH. culties which may be encountered if film is reeled while the emulsion is dry, but the base still moist, are discussed by Talbot.1 In Table 2 the time to sensible dry ness is given for various Eastman nitrate motion picture films developed in a typical commercial processing machine. The regular negative type films require longer to dry than the positive films, because the negative emulsion is thicker and, therefore, holds more moisture (W in Eq (1) is larger). The moisture content of the film in per cent, and in grams per linear foot of 35-mm film, just after the squeegee, and at the point of reeling, is also given in Table 2. However, it should be remembered that