International projectionist (Jan-Dec 1950)

and-down motion. This latter tactic utilizes excess cement, and will only cause trouble, usually a 'bumpy' patch. "Once the cement is applied, it is important that the pressure clamp be brought down immediately: lower it slowly but firmly instead of with an abrupt clamping-down, which tends to splash the cement and thicken the splice. Splicing Duplitized Prints "The removal of the sub-layer is somewhat more critical on safety than on nitrate base and requires close attention on the part of the projectionist. Duplitized film, whether safety or nitrate, has emulsion on both front and back surfaces and is much more difficult to splice than single-coated stock. All duplitized films (Trucolor, Magnacolor, Cinecolor, etc.) must have both emulsions and both subbases scraped . . . before a secure joint can be made."6 FILM cements are not glues or mucilage-type adhesives. They are solvents of film base, and are able to join two pieces of film by softening them so that they flow together and harden to form a weld. There are many solvent chemicals which may be used in the formulation of 6 "Safety Film: Projection Factors," by Henry B. Sellwood; IP for November, 1948, p. 9. Theatre-Goers APP&QH and 15? ACCLAIM SOUNDMASTER m IN-A-CAR SPEAKERS That's Why Over 280 Drive-ins Installed Them in 1949 Alone. This same popular speaker now offers several important improvements, yet is available 3t a lower tost than ever before. The deluxe speaker (above) with tinted plexi-glass ramp marking light in the junction box is also available. Glowin-the-dark volume control knob is optional on all speakers at no extra cost. See it today at any Ballantyne Dealer, or write for details. Ballantyne Drive-in Theatre equipment is availab'e either in "packaged" combinations, "packaged priced" for any size drivein, or, in the Ballantyne "Turn-Key" drivein, the original plan for completely building and equipping a theatre at a low contract price. THE BALLANTYNE CO. OMAHA, NEBR. film cements. Following are some of the simple solvents which can be used alone as film cements for the various types of film. Nitrate film: Methyl alcohol, acetone, methylethyl ketone, "cellosolve," methyl "cellosolve" acetate, diacetone alcohol, glacial acetic acid, ethyl a< etate, isoamyl acetate, and butyl acetate. Diacetate (old-type) safety film: Acetone, methylethyl ketone, methyl "cellosolve" acetate, diacetone alcohol, dioxane, glacial acetic acid, and chloroform. Triacetate (high-acetyl) safety film: Diacetone alcohol, dioxane, glacial acetic acid (especially when warm or mixed with other solvents), and chloroform. Most film cements however, are mixtures of several solvents in which a small quantity of film-base material has been dissolved. Multiple Solvents Desirable Two or three solvents mixed together are usually more effective than any of them used singly. Film-base material is usually dissolved in the solvent mixture to increase the viscosity of the liquid, to hasten the "biting" and "setting," and to permit stronger splices to be made by preventing an excess of film-base from being dissolved and subsequently lost when it squeezes out from the join. Occasionally a trace of some "plasticizer" such as castor oil, camphor, butyl phthalate, or tricresyl phosphate is added to insure supple, non-buckling splices which retain their strength and flexibility indefinitely. Only the kind of cement compounded for the type of film being spliced should be used — regular nitrate cement for nitrate film, triacetate cement for highacetyl safety film, and "double-purpose" cement for either type of film or for both in mixed splices. Film cements made for the old-type diacetate safety film should not be relied on for splicing the new high-acetyl (triacetate) film. Only small quantities of film cement (no more than one pint) should be kept on hand, as some types are chemically unstable and deteriorate with age. Stock bottles should be kept tightly stoppered at all times, and, most important of all, the dispensing bottle kept on the filmrewinding bench should not have a capacity greater than one fluid ounce. Nearly all film cements are hygroscopic, readily absorbing water vapor from the air. The frequent exposure of the cement in the dispensing bottle to the air allows moisture to be taken up by the fluid, and also permits certain of the solvents to evaporate, thickening the liquid and changing its composition. Film cement which contains moisture and dirt, or which has lost a large percentage of the more volatile of its ingredients, is manifestly unfit for use. In the early days of the projection art, it was not unusual for the projectionist The first major screen improvement in 30 years! CYCLMMIC Custom Screen 'Patent applied for NO PERFORATIONS 20% MORE LIGHT and BETTER VISION from EVERY SEAT! B. F. 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