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1949 LUBRICATION OF FILMS 287
aid of the unfatigued nose. Carbon tetrachloride can be used if precautions are taken to prevent its vapors from escaping into the workroom air — even in small amounts.
If there is room inside the drying cabinet, between the point of dryness of the film and the take-up reel, for the installation of the lubricating device, this section of the cabinet can be blocked off and the carbon tetrachloride vapors drawn off to the outside of the building with the aid of an auxiliary fan. Such a system is in operation in several laboratories. An apparatus for the continuous application of wax solutions to film is shown in Fig. 1.
Fig. 1 — Rollerwick applicator for wax solutions.
The apparatus consists of a plush-covered roll which is driven slowly, generally in a direction opposite to that of the film, by an alternating-current motor operating through a thyratron speed-controller. Provision is made for maintaining a constant liquid level and for varying the extent of wrap of the film on the drum. In general, the film speed is fifty times that of the plush, but this varies somewhat with the lubricant used and the condition of the film. The extent of wrap also varies with the lubricant and the film; in general, the smallest amount of wrap that permits uniform coverage of the film should be used.
All of the lubricants presented in the tables have been applied at a film speed of 100 feet per minute. This is the upper speed of the machine and there is no apparent reason why higher speeds cannot be attained with adequate drying capacity.