American cinematographer (Jan-Dec 1928)

January, 1927 AMERICAN CINEMATOGRAPHER Twenty-five Lubrication of M. P. Film (Continued from Page 20) the perforations has been described by J. G. Jones.1 This 1 "A Film Waxing Machine" by J. G. Jones, Trans. Soc. M. P. Eng., No. 15, 251 (1922). consists essentially of two parallel thin steel discs separated by a distance of 1-3/32" rotating in a vertical plane. The discs dip into a bath of molten paraffin wax and apply the wax to the film at their upper edge. The quantity of wax applied is controlled by the thickness of the discs, the temperature of the molten wax, and the rate of travel of the film. Precautions to be Observed when Edge Waxing The above method of lubrication is entirely satisfactory providing the wax is applied correctly, and no better lubricant than paraffin wax is known to date. However, if the temperature of the molten wax is not sufficiently high during application, too much wax is applied by the discs and this does not solidify sufficiently before the film is rewound. This causes the wax to cement the edges of the film convolutions so that on rewinding, particles of wax are torn away from the film and these tend to encroach on the picture area causing spots and blotches on the screen. This is harmful particularly in the case of film with an edge sound record. Another very serious danger resulting from the replication of an' excess of wax arises if the projector is threaded while hot with 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 was 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 ol 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 running each reel through the piojector 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 several thousand feet had been projected when enough wax had collected to hold the film from being properly drawn through the gate. After cleaning the piojector, 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. Supplied as $60 ^ special equipment on DeVry and other M. P. Cameras Since 1884, manufacturers of fine View Cameras and Lenses. Write for complete catalogue of fine apparatus for the Still Studio. Qundlach-Manhattan Optical Co. 900 Clinton So., Rochester, N. Y. AKELEY SPECIALIST A. Le. Roy Greiner Phone GLadstone 7046 ELMER G. DYER Akeley Specialist 2 1-2 Years With Universal THAT'S ENUF SED! FOR. HENT BELL HOWELL : AND i AKELEY CAMERAS With or Without Cameramen SEIDEN CAMERA EXCHAN G E 729 Seventh Ave. N.Y.c' B ryant 3 95 1 Wire us for any New York Scenes you may need Prices Reasonable Akeley Expert Gaylord A. WOOD GLadstone 0033 FOR RENT: BELL & HOWELL 1821% N. Wilcox