International projectionist (Jan-Dec 1950)

to make his own film-joining mixtures, commercial ready-mixed cements being practically unknown. But nowadays most projectionists use the commercial products in order to avoid the trouble of obtaining separate solvent liquids and mixing them together in the most satisfactory proportions. Reconditioning, Storage of Film The "rejuvenation" of absolutely wornout film is an utter impossibility. The most that can be done to salvage a wornout print is to reprint it anew on fresh raw stock — a delicate procedure when the original negative is unavailable, thus making it necessary to prepare a duplicate negative from the damaged positive. As a rule, projection prints may be maintained in good condition for a surprisingly long time by frequent inspection and prompt correction of all discoverable defects: (1) weak splices (2) torn and cracked perforations (3) torn and roughened edges (4) scratches (5) the presence of dirt and oil and (6) brittleness. With the exception of 4, 5, and 6 these repairs have been discussed in connection with the inspection and repair of prints in the projection room. Scratches cannot be removed from film, of course, but if they are not too deep, the "rainy" effect they give on the screen (together with surface noise in the sound) can be mitigated slightly by cleaning the film to remove the grime which has accumulated in them. When only a few feet of film are defaced by deep scratches, the defective portions of film may be removed or, if this is not feasible, the scratches may be painted over with black Movietone lacquer in the dark portions of the image. The latter expedient is most valuable on "fades." The type of defacement caused by "sprocketing" is irremedial and film having sprocket marks in the soundtrack area is definitely unusable. Cleaning Reels of Film The cleaning of entire reels of film requires special film-washing and polishing machines, and should never be attempted in the projection room unless the proper apparatus be at hand. These machines wash the film in clean carbon tetrachloride and subsequently polish the film by applying a carbon-tetrachloride solution of carnauba wax and buffing. The cleaning of film by drawing it through a pad of cloth moistened with carbon tetrachloride is not recommended except for very short lengths of film to which extra time and care may be devoted. The pad becomes dirty very quickly and serves only to scratch the emulsion and merely redistribute the oil and dirt on the film without removing very much of it. The brittleness of old nitrate films cannot be wholly remedied, but a substantial measure of tensile strength and pliancy may be restored to the film by storing the film for a sufficient length of time in a vault or air-tight can (film "humidor") in which specially treated blotting paper has been placed. The blotting paper is prepared for this purpose by wetting it with an acetone solution of camphor and, when the acetone has evaporated, leaving a deposit of camphor crystals in the fibers of the paper, moistening it with plain water or, better, a dilute solution of glycerine in water to prevent too rapid drying. The camphor solution is made by dissolving a V^-ounce block of camphor in about 4 fluid ounces of acetone. A suitable gycerine solution is made by mixing 1 fl. oz. of glycerine with 4 fl. oz. of water. The camphor-impregnated blotter should be definitely moist, but not dripping wet. The moist, camphoraceous vapors given off by the humidor blotter will also benefit safety films. 'Hardening' Bath for Film The emulsion of film which has been exposed to ammoniacal or alkaline fumes may have become too soft and sticky to permit projection of the film. This can be remedied by treating the film in a "hardening" bath consisting of: Formaldehyde (37%) 3 fl. oz. Potassium carbonate 3 oz. Water 1 quart If the emulsion is hardened too much, GOLDE AUTOMATIC ENCLOSED .^JIONND ALWAYS V WORKS! The operators* favorite . . . silent and safe! U. L. approved. Eliminates fire hazard. Positive friction . . . can't clinch film. Tilt-back case . . . reels can't fly off. Microswitch safety cut off . . . when door opens or film breaks, motor stops. * At better theatre supply dealers. GOLDE MANUFACTURING CO. 1222-P W. Madison St., Chicago 7, Ml. I however, the film will be so brittle that it cannot be bent sharply without snapping it asunder. There is little to be said concerning the long-term storage of film. Temperature and humidity are important factors in successful film storage. Tests have proved that film keeps best at about 50° F. (10° C.) and in an atmosphere containing about 50% relative humidity. Nitrate prints stored under these ideal conditions will retain good projection quality for about 50 years; and it has been estimated that high-acetyl safety film will last for about 1,000 years. The writer has a few reels of nitrate film about 15 years old and projected hundreds of times. These have not been stored under favorable conditions, yet the films are still flexible and tough and give excellent screen results. The longitudinal shrinkage of these films is about 0.7%. [To be Continued] How Many? Was this copy dog-eared when it came to you? How many men read it ahead of you? You would receive a clean, fresh copy if you had a personal subscription — and you wouldn't have to wait — you would be first to read it. Use coupon below. INTERNATIONAL PROJECTIONIST, 19 West 44 St.. New York 18, N. Y. □ 1 year — 12 issues — $2.50 □ 2 years— 24 issues — $4.00 Foreign and Canada: Add 50c per year. Enter my subscription for Name Address City State 34 INTERNATIONAL PROJECTIONIST • MARCH 1950