The Exhibitor (Aug-Nov 1948)

TAIL FLAME OF THE NEW ELECTRONIC ARC RESEMBLES THAT OF THE OLD HIGH INTENSITY. St. Louis Sights Big TESMA Show Next Week Will Help Keep The Town’s Name Green PHYSICAL rilEAritE Volume III Number 10 September 22, 1948 Next week in St. Louis theatremen from all parts of the country will be high pressured with sales talks, pamphlets, broadsides, exhibits, and dem¬ onstrations extolling the wonders of all manner of equipment related to the industry. To help these conscientious operators block out their agendas at the annual TESMA trade show we’ve gathered some data on a few items — and they are only a few — which actually incorporate im¬ provements in basic design. The high-spot report, naturally, does not take into account the new gimmicks and little doohickeys put out by the gadget manufacturers, with whom novel plastic devices are epidemic. It does take into account, though, the major array pre¬ sented by projection and sound heads, arc lamps, chairs, theatre television, and drive-in theatre screen towers and toll systems. In St. Louis the movieman can find out how substantial the countless mechanical wonders that manufacturers kept promis¬ ing him throughout the late war are turning out to be. The varied collection of equipment will be spread out for his inspection on September 27, 28, 29 and 30 in the Jefferson Hotel under the banner of the Theatre Equipment and Supply Manufacturers’ Association, Inc., (TESMA) with headquarters in Chicago. Tail flame of the suprex arc, regularly em¬ ployed today in projection lamps, is a short angular one. It succeeds the high intensity. FOREST ARC LAMP A fine example of \Yhat we mean by a product being improved in ways more basic than appearance is the Forest arc lamp, according to our information. At the show the visitor should tear himself away from such catchy phenomenons as that of his image being instantly projected on to a television screen long enough to inspect it. More than a year ago, while putting the finishing touches on a new carbon feeding mechanism, Forest engineers stumbled on what looked like a startling new technique for burning the carbons — an improvement upon the so-called suprex or simplified high intensity method. It held out such bright hope for the future that the com¬ pany — after announcing the production of a new lamp — withheld the lamp from the market. Engineers went to work on the discovery. The result of their research will be unveiled at the TESMA show in Forest’s new “Electronic Projection Arc Lamp.” With the luminosity of the arc already second only to that of the sun, the new “electronic arc” is said to produce “much more light with the same energy con¬ sumption.” This, too, with “a marked saving in carbon consumption.” Just how much more brilliancy is produced seems to be a trade secret. The new light source is similar to the old high-intensity arc in that the tail flames of both are longer than the tail flame of the suprex arc, which has a short angular one. The white flame in the tail flame of the new electronic arc seems to be more intense than that in the tail flame of the high -intensity arc, however. Beyond this the similarity ends. The new arc does not rotate its carbons nor place them at an angle to each other. (All this is clearly outlined in the accompanying illustra¬ tions.) Quick Review Before entering into a more detailed analysis of the new electronic arc, it would be well for the theatreman to review the fundamentals of light production quickly. The primary source of arc light is the burning of rare earths and chemicals (their actual compositions being well guarded trade secrets) concentrated in the core of a carbon. These are burned in gaseous form after being volatilized by electric current. The action creates a saucer shaped depression in the tip of the positive carbon, called a crater. The secondary source of arc light is the col¬ lection and convergence by a glass con¬ denser of the brilliant light engendered by the burning of the gases. (More about this when we come to the superheat cre¬ ated by huge arc lamps at some drive-ins.) Forest says that “the very high intrinsic brilliancy” of their electronic arc is achieved by “compressing and confining {Continued on page 18) PHYSICAL THEATRE DEPARTMENT of THE EXHIBITOR PT-7