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

Record Details:

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474 JENNINGS, STANTON AND WEISS November forms have been used successfully. To keep the solution from diffusing to undesired areas, its viscosity is raised by the addition of a thickening agent. Sulfiding Solution Distilled water ( 125 F) 750 cc Sodium Carboxymethylcellulose, medium viscosity 20 g Sodium Sulfide, nonahydrate 63 g Water to make , i 1 Stir thoroughly with a mechanical stirrer and filter while hot. Cool to room temperature before using. The film should receive a 30 to 60-sec water rinse following the bleach bath to eliminate excess ferricyanide solution. At this time, the film is removed from the machine and prepared for the soundtrack beading operation. An air blow-off should be used to remove excess liquid from the surface of the film. Best results are obtained when the emulsion is partly dried by passing the film through a drying chamber. The film travel is so arranged that a developing time of one full minute is allowed following the application of the sulfiding solution. At the end of this period, the sound track area is subjected to a small, high-velocity water stream directed to wash the treating solution toward the perforations. This removes the excess sulfiding solution. The film is now returned to the machine for completion of the normal process, the next treating bath being the second fix. Sound tracks to be sulfided are exposed in a slightly different way than are magenta tracks. While it would be desirable from the point of view of sharpness to print the track in the top layer only, the amount of silver in the magenta emulsion alone is too low to produce a silver sulfide track of the desired density. Thus, it is necessary to utilize the lower emulsions by printing with white light, even though some loss of high-frequency response results. The following operating conditions were found at the Du Pont laboratories to give satisfactory results. A variable-area negative recorded on Du Pont Type 201 Sound Recording film was exposed to give a negative track density of 2.5 with the film processed to gamma 3.5. This track was printed onto Type 275 with unfiltered incandescent light and sulfided as described. Cancellation of 30 db or more occurred at positive track densities in the neighborhood of 1.2. A variable-density sound negative recorded on Du Pont Type 226 processed to a IIB gamma of 1.5 yielded a color sound print with minimum intermodulation at positive track densities about 0.6.