International projectionist (Jan-Dec 1945)

Cleaning Aids in The Projection Room BOTH as routine, to keep his apparatus in decent and trouble free condition, and on special occasions, as when a generator bearing threatens to "freeze", the projectionist is faced with cleaning jobs. Mechanical aids, such as brushes, rags, lens tissue and vacuum cleaner are obvious helps. Liquid or "chemical" cleaning aids are not always so well understood because they are of several types, and the right type must be used for a given job. They act primarily by dissolving the dirt, and the kind of liquid to be used depends upon the kind of dirt to be dissolved. The type of apparatus on which the cleanser is to be used must also be considered. Classifying these "chemical" aids in the broadest possible sense, they are of PROJECTION ARC LAMPS Deliver the snow-white light essential to satisfactory projection of Technicolor pictures— twice as much light as the low intensity, with but slight increase in operating cost. rAN QUALIFY FOR NE W caTION. NATIONAL Division of Notional • Simple. • Blud worth. Int THERE'S A BRANCH NEAR YOU three general types. One, of course, is water — hot or cold. A second consists of non-aqueous solvents — liquids that dissolve substances which water won't attack; for example, carbon tetrachloride. The third and most numerous type might be called coupling agents — something that couples water with substances that normally do not dissolve in water, enabling the water to dissolve them. A more correct but narrower term for "coupling agent" is emulsifying agent. Common soap is an emulsifying agent, but by no means the best one for all purposes. What cannot be cleaned with water — as applied, for example, with a damp rag — may perhaps be cleaned by substances of the second type named, carbon tetrachloride, for example, applied by means of a rag. In the case of a motor or generator bearing, where the lubrication has gummed and must be removed and replaced, carbon tetrachloride also is used. So is kerosene, warm or cold; and hot oil — the same lubricating oil — is very useful. Wherever oil or grease must be removed water alone can be ruled out as ineffective. Oil and water don't mix. An emulsifying agent is needed to make them mix — soapy water will remove grease that plain water won't touch. But there are also direct solvents, as stated, depending on the type of oil. In addition to those already mentioned, alcohol and acetone may prove effective. Coupling' Agents Alcohol and acetone, although solvents in their own right, can act more or less as coupling agents — that is to say, some substance not soluble in water can often be washed away by mixtures of alcohol and water, or of acetone and water. Tri-sodium phosphate, or tetrasodium phosphate, which can be obtained either at the drug store or from the firm that supplies the theatre's porters with cleaning materials, are highly effective on some problems. Many commercial soap powders and cleansers, obtainable at any grocery, are mixtures of these phosphates and common soap. Hydrogen peroxide — which actually consists of about two percent peroxide and 98 percent water — acts as a coupling agent in cleaning out projector heads after film fires. The action in this case possibly is one of oxidation rather than an emulsifying action. Common lye has a very powerful action on some types of grease in still another wayit converts the grease to soap. The practical problem confronting the projectionist, however, in his choice of cleaning agents, boils down to three simple, practical points: the agent must be effective, it must not leave any harmful 26 INTERNATIONAL PROJECTIONIST