International projectionist (Jan 1963-June 1965)

form thickness, therefore, a special tvpe of clear gelatine having both "water-loving" I hydrophilic I and "u ater • dreading" i hydrophobic l properties is chosen for the all-important sublayer. What about the plastic film-base material, itself? A gelatine film, alone, would be too fragile and dimensionally unstable to serve as a motion-picture film. \ relatively tough transparent support material must he used to give the film the uecessar) strength and rigidity. \a matter of fact, the qualities of the base are largely responsible for the working and handling properties of all the different available types of motion-picture film. Yi hen the Photographic emulsion .£$ Gelatine substrate Plastic base, or "emulsion support" Fig. 1 — Motion-picture film consists of a relatively thick plastic base upon which is coated (1) a thin transparent layer of banding gelatine and (2) a somewhat thicker layer of photographic emulsion consisting of silver salts in gelatine. The emulsion of dye-coupler color film consists of three or more very this layers. projectionist blames a specific kind of film for poor splicing characteristics, excessive buckling, rapid wear of the perforations, etc. he usuallv land rightly) blames the base material. I wo broad categories of film base, nitrate and safety, have been known since the early days of the art. but the chemical nature of safety base has been changed repeatedly to improve its working qualities and to make it comparable to nitrate base in strength, toughness, rigidity, flexibility, and resistance to the wear and tear of repeated projections. Even though it was preferred for half a century for professional motion-picture film because of its unequalled physical properties, nitrate base is dangerously inflammable — almost explosive — and liable to excessive shrinking and to spontaneous deterioration with the passage of time. Nitrate base is a form of cellulose nitrate made by treating cotton or paper with strong nitric and sulfuric acids. The pure cellulose nitrate, called Collodion, is subsequently dissolved in a solvent I acetone or a cheap mixture of alcohol, International Projectionist June, 1964 ether, and banana oil ) containing "plasticizers" i camphor and tricresyl phosphate I to increase the toughness and pliancy of the material as well as to reduce the tendency to shrink and become brittle. The common name of the completed base material is celluloid, first manufactured bv John Wesley Hyatt in 1872. The first celluloid photographic film was produced in 1887 by Hannibal \\ illiston Goodwin of Newark. N. J., who received an order dated September 2. 1889 from Edison for one roll of such film at $2.50. \ year earlier, however. Edison had obtained nitrate film from George Eastman, who must be regarded as the first manufacturer of a satisfactory nitrate film stock. Safer) motion-picture film is very nearly as old as nitrate stock, but until the late 1940's it was larger) confined to amateur and other nonprofessional applications. The oldtvpe cellulose diacciair safet) base was first made on a large scale in 1908 by the German chemical firm of Bayer (the originator of aspirin). This base material is made bv substituting acetic acid lor acetic anhydride i for the nitric acid of the usual celluloid-manufacturing process: and in order to make the safet) film soluble in acetone and other common film-cementing solvents, the degree of acetylation was purposely limited hv hydrolysis. Vspirin and di acetate film base were an appropriate combination, for the costliness, low tensile strength, shrinkage, and excessive brittleness of the old-type safet) film were productive id headaches aplentv . The professional motion-picture field had no choice but to reject diacetate film from the outset, and in spite of w idespread dissatisfaction with the dangers of nitrate film. By using other organic acids in conjunction with acetic acid, a num ber of "mixed-ester" celluloses have been obtained and used as film base. The best known are cellulose acetobutyrate and acetopropionate. the latter having constituted the safety film of Eastman Kodak manufacture from 1937 to 1948. Although somewhat more satisfactory than diacetate base, acetopropionate film lacked the strength and durability. The big break-through in safety film was the discovery of German scientists that a cellulose somewhat more highl) acetylated than the diacetate* furnishes a material for film base which more nearly resembles nitrate base in working properties while retaining the advanlage (Continued) THE VERY FINEST PROJECTOR PARTS ARE MADE BY There's nothing like them for precision manufacture, close inspection, efficiency in operation, dependability and long life. Obtainable from your Theatre Supply Dealer. SINCE 19 0 8 MACHINE WORKS 463S W. LAKE ST., CHICAGO 44, ILL. TELEPHONE— AREA 312— ES 8-1636 13