International projectionist (Jan-Dec 1945)

residue, and it must not cause corrosion. Effectiveness can always be determined by trial and error; the other two points will require either some understanding of the actions involved or else a small bit of memorizing. As to harmful residues: any substance which does not evaporate completely is going to leave a residue, which may 01 may not be harmful. Soap, unless most thoroughly flushed away, will leave a soapy film. Tri-sodium phosphate an J similar detergents, unless thoroughly flushed away, will leave crystalline deposits. Hot oil used for cleaning bearings and grease cups is almost certainly going to leave an oily film behind — that is why only the same lubricating oil should be used. Kerosene is for that reason less satisfactory; some will remain to dilute the new lubricant at first. However, it is slowly volatile and in time it will all evaporate. Carbon tetrachloride will evaporate promptly. Acetone, alcohol and carbon tet all evaporate much faster than water. They leave no residue. Water leaves none, neither does hydrogen peroxide. However, water and hydrogen peroxide are a little slow to evaporate, and they may cause some corrosion before they disappear completely. Hydrogen peroxide has a corrosive effect on metals; this applies to water also, but to a somewhat lesser extent. Soapy water not thoroughly flushed off is particularly corrosive because any film that remains behind will be a film of water as well as soap, and the water won't dry off for a very long time. The soap will hold it in contact with the metal, keeping the metal moist, possibly for weeks. Stirring kerosene into water, up to about one part kerosene to two parts water, reduces the possibility of the water causing corrosion of metal with which it comes into contact. Kerosene and hot oil, alcohol, acetone and carbon tetrachloride produce no appreciable corrosion. Lye is extremely corrosive. Acetone an! even alcohol have a solvent effect on motion picture film, and should not be used, or used only with care, in cleaning film or grease. Hot water exercises a solvent action on the emulsion of film, tending to soften or dissolve it. Even cold water may cause the emulsion to swell after a period of time, but can be used for cleaning film with perfect safety unless the film is going to be left wet for hours. The "organic" solvents — carbon tet, alcohol, acetone — should not be used in cleaning compound lenses. Should they be able to seep into the cement that holds the lenses together, they may dissolve it. Many of the aids here named are used in commercial cleaning compounds. In order to avoid their mis-use, always apply such compounds strictly according to directions, and only for the purposes and conditions specified. Many of these aids also can be obtained in commercial form under other names. Impure carbon tet is used in fire extinguishers; mixed with kerosene or naptha it is found in popular dry cleaning and sta"in removing compounds. Acetone is a component of many film cements, and is found also in nail polish remover and in varnish and lacquer removers. H. W. FORSTER DIES Herbert W. Forster, 47, advertising manager of Western Electric Company, died suddenly on March 30 at the Roosevelt Hospital, New York, following a heart attack. Mr. Forster lived in Rockville Centre, Long Island, and is survived by his widow and two children. He became the company's press representative in 1930 and later as information manager conducted its information service both to the public and to employees. Articles by him have appeared in the popular, trade and technical press in this country and throughout the world. He became West em Electric advertising manager in 1940. THOUGH you may not neglect your best girl to read your copy of the RCA Theatre Television Handbook — you will be vitally interested in learning the what, how and why of theatre television from the booklet's timely articles and discussions. The Handbook was designed for projectionists, but also contains news of television developments of interest to exhibitors and theatre managers — such as television reception and largescreen projection. There are chapters dealing with the commercial possibilities of television, handling of programs, audience response. RCA'S television experience is backed by a quarter centurv in the field of electronics and includes television installations at the New York World's Fair in 1939, and demonstration large-screen television projection at the New Yorker Theatre in 1941. This new book is offered by the RCA Service Company as an aid to projectionists and exhibitors in preparing for the advent of theatre television. Send for vour free copv, today! Address: RCA Service Companv, Inc., Box 70-177 M, Camden, New Jersey. RCA SERVICE COMPANY, INC. A Radio Corporation of America Subsidiary FREE! NEW BOOK ON THEATRE TELEVISION Don't wait — get your copy of this informative book on Theatre Television right away. No obligation. i_ . RCA SERVICE COMPANY, Inc., Box 7C-177 M.Camden, N. J. Name Theatre Are you: Manager? Projectionist? Address City State APRIL, 1945 27