International projectionist (Jan-Dec 1950)

NBFU Classifies Safety Film Official Communication from the National Board of Fire Underwriters Discusses Comparative Characteristics of Nitrate and Acetate Film Stock FOLLOWING an extended investigation, acetate base film in the form of ribbon for motion pictures was listed by Underwriters' Laboratories, Inc., as slowburning, the fire hazard being classed as somewhat less than that of common newsprint paper in the same form and quantity. Motion picture safety film having a cellulose acetate base is now being marketed for commercial and general use. It is claimed that this film has a greater projection life and is otherwise superior as compared to the older type of cellulose acetate film. This type of film may be identified by the words "Safety Film" printed at frequent intervals along the edge. In case of doubt, acetate film may be distinguished from nitrate by a burning test, using only a small piece of film, and burning it in a room where there is no film and no fire hazard. Nitrate film will burn fiercely; acetate film will burn quietly. Comparative Ignition Temperatures The ignition temperature of Cellulose acetate is between 700 and 800° F., as compared to about 300° F., for cellulose nitrate. A temperature of about 500° F. is required to produce the decomposition of cellulose acetate film. In the neighborhood of this temperature the evolu MOTOR MAINTENANCE (Continued from preceding page) flow of current, but a slip-ring collector allows unchanging D.C. to be fed to the rotor electromagnets from the exciter. The most noteworthy feature of synchronous motors is the fact that they must revolve in exact synchronism with the alternations of the line current fed to the stator coils. If an excessive load or a sudden voltage drop causes them to slow down, they will grind to a dead stop. Unless the exciting dynamo is cut out, the induction of powerful alternating currents in the rotor may damage the motor or the exciter. Serious accidents of this nature have occurred with large synchronous motors. Synchronous motors are seldom used in the theatre, but one or two soundhead manufacturers have made 3-phase. x/4 H.P., 220-volt synchronous projector motors. Such motors are likely to be troublesome in this application, and offer no advantage over constant-speed induction motors. [To be Continued] tion of fumes in material quantity occurs. These fumes are irritating and suffocating, but not considered to be toxic under most conditions. The decomposition of cellulose acetate film, once started, does not continue except under conditions where there is an external source of heat. On the contrary, in the case of cellulose nitrate film the decomposition continues when once started, even in the absence of external source of heat. This difference of decomposition is. therefore, of great importance from the fire and life hazard standpoint. Furthermore, great volumes of explosive and toxic gases are given off from decomposition of nitrate film, especially in a restricted supply of air. thus contributing to the life and fire hazard. Slow Combustion Vital Factor The rate of combustion of cellulose acetate film is relatively slow and the amount of heat evolved is of a low order, being much less than that of paper or wood. The most important safety factor with reference to cellulose acetate film is in its slow combustion, and any fire can be easily extinguished by the application of water or smothering, much in the same manner as fires in ordinary combustible materials. The time will, no doubt, come when nearly all pictures will be on safety film; but there may be nitrate films in circulation for some time, and because of this every precaution should be taken to avoid any relaxation in the regulations prescribed and methods imposed for the safe handling of flammable nitrate films. Separate Storage Facilities The safety factor supplied by the new acetate film can be taken advantage of by arranging its storage apart from any nitrate films. By this segregation., loss possibilities will definitely be reduced, and as nitrate inventories are progressively diminished their isolated confinement will tend to further control hazard possibilities. In existing film exchanges, this segregation can be readily controlled by having separate film vaults for safety and nitrate films, and marking their doors with the words Safety Film in green, or Nitrate Film in red. Similar isolation of safety films from nitrate films can also be practiced using specially identified rooms for the safety film with such meas ures for protection against loss as may be desired. Small amounts of safety film can be appropriately stored in ordinary steel filing cases, but if they are of high value specially protected cabinets of the type designed for film storage should be given consideration. Positive Identification Needed In order to insure the degree of safety now provided by the new film it is suggested that all safety films be unmistakably identified by reel bands bearing in prominent letters the words SAFETY FILM printed in bright green. All record cards and other control items that pertain to these films should also be printed in the same green color and bear as their main feature the words SAFETY FILM. In contrast, all flammable nitrate films should be equipped with reel bands printed in bright red with the words NITRATE FILM, with their record items correspondingly identified. Film-handling personnel working under this plan for segregating the two types of film should take special care to prevent intermixture of the two types, and there should be exacting supervision of storage facilities to minimize all possible loss. By positive and intelligent management the safety factor provided by this new film base can immediately benefit all engaged in motion picture film activities. If such a plan for careful segregation is not followed, any place where both types of film are handled should follow for all film the safety precautions prescribed for nitrate film. New Kodak Flexichrome Booklet A new Kodak Color Data Book describing the Kodak Flexichrome Process has just been announced. The publication, 40 pages with six pages in full color, provides complete working instructions for the process, together with details of special applications. It includes not only suggestions helpful to the beginner, but also valuable guidance for the advanced worker. The text for the new Data Book is divided into the following sections: The Process in Brief; Materials and Equipment; The Negative; Making the Print; Coloring the Print; Suggestions for Coloring; Surface Coloring; and Special Applications. Punched to fit the Kodak Color Handbook, the booklet is available at 50 cents per copy from all Kodak dealers. Dr. H. L. Bohm Dies in England News note from England: Dr. H. L. Bohm, formerly of the German UFA organization and who visited the United States in the early days of sound picture development, was killed recently in London when he fell in front of an underground train. His colleagues regarded Dr. Bohm as an outstanding worker in the technological arts. INTERNATIONAL PROJECTIONIST November 1950