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CRABTREE, SANDVIK, AND IVES
[J. S. M. P. E.
SUMMARY AND PRACTICAL RECOMMENDATIONS
Sound record prints can be satisfactorily lubricated by applying a thin coating of a solution of paraffin wax in carbon tetrachloride along the edges of the film in the perforation area and drying. This treatment is superior to the application of solid or molten wax inasmuch as the wax does not flake off or encroach on the sound track during rewinding or projection, which would produce ground noise.
The application of the wax is accomplished by means of two steel disks which dip into the wax solution. The disks should be about 0. 15
W 20 30 40 50 60 70 80 90 KX> 110 l«0 130 10 20 SO 40 50 «O 70 80 *> 100 HO 110 130
0
-30
10 20 30 40 50 60 70 80 90 100 110 120 130
FIG. 4. Curves showing change in relative ground noise volume level in decibels.
inch wide and so spaced that they are in contact with the film from the edge inward 0.15 inch so that the area lubricated will correspond closely with that under the tension shoes in the projector gate. The quantity of wax applied is varied by changing the rate of rotation of the disks in relation to the speed of the film. For a film speed of 50 feet per minute, a disk 3 inches in diameter should so rotate that its peripheral speed is about one-third this value when immersed onehalf inch in a 1.0 per cent solution of the wax. The quantity of wax thus applied is about 0.30 to 0.35 gram per 1000 linear feet of film. For higher speeds, the wax solution should be applied to the disks in a suitable manner, such as by means of an application roller dipping into the wax solution. After application the solvent is quickly evapo