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Lubrication of Film — Crahtree and Ives 529
newly waxed film. As the projector cools, the wax solidifies and holds the film so tightly that on starting the projector, the intermittent sprocket may tear out the perforations instead of pulling the film down through the gate. Since the fire shutter opens immediately when the projector starts, more or less film is apt to be burned up if the film does not start to move down promptly past the aperture.
A series of practical tests were made in this connection to determine the exact conditions under which candle edge waxing or Eastman edge waxing tends to cause the above trouble.
Film was first waxed with a waxer of the candle type which normally applies an excessive quantity of wax. After focusing the light ray from a 30 ampere reflector arc on the aperture opening of a Simplex projector for 30 minutes, this projector became heated to a temperature which would normally exist after the projection of a reel of film. Film waxed in the above manner was then threaded in the heated projector and left to cool for forty minutes. After cooling for such a period the projector had attained room temperature and any wax in the gate had hardened. On starting the projector, the intermittent sprocket tore through the perforations leaving the film stationary in the gate. Upon examination of the samples, it was found that the wax had softened and collected in the perforations and had cemented the film to the film tracks and the pressure springs.
The possibility of this difficulty occurring when film was waxed with the Eastman waxer was then determined. The projector was cleaned thoroughly, and a one thousand foot reel of film waxed with the Eastman waxer was projected in the normal way. Immediately after projection the projector was threaded with a length of unwaxed film and allowed to cool. When the projector was started the film pulled down through the gate with no difficulty. Several thousand foot rolls were then waxed with the Eastman waxer and projected in thousand foot units, each reel being run through the projector only once. After the projection of each reel the projector was threaded with unwaxed film allowed to cool, and then started. No trouble was experienced until seven thousand feet had been projected, when enough wax had collected to hold the film from being properly drawn through the gate. After the projector had been cleaned, it was possible again to project several thousand feet of waxed film before enough wax collected to cement the film, but after each 8,000 or 10,000 feet, the trouble was almost sure to occur.