International projectionist (Jan-Dec 1955)

Cronar, New DuPont Film Base, Soon to Be in Production Winter field tests in theatres are scheduled as an additional check before distribution of this film. THE TIME when "Cronar," Du Pont's new film base, will be regularly used in the manufacture of motion picture release prints is drawing closer. Extensive field tests on this new base, which is a polyester plastic similar to Nylon, have been conducted in theatres scattered throughout the country. The film was found by projectionists to stand up well under hard use, but one objection was brought forth. Some projectionists found that they experienced difficulty in keeping Cronar film in focus. Further laboratory tests are now being made by Du Pont to determine the exact cause of this problem and eliminate it. Additional field tests will be held this Winter when Cronar-base prints of the film, "Desperate Hours," will be distributed to theatres in several areas. These tests will probably be the final check on Cronar before commercial distribution. A new Du Pont factory located at Parlin, N.J., will soon begin largescale production of Cronar film. It has also been announced that the Eastman Kodak Co. has been licensed to manufacture the film base under Du Pont patents. Thinner Than Acetate Cronar is different in a variety of ways from the cellulose triacetate base now used almost universally for motion picture release prints. Its principle advantage is that it is tougher than acetate, making it much more resistent to tearing and kinking. Because of its toughness, it can be thinner, allowing as much as 35% more film to be wound on a reel. Cronar base is 4 mils (a mil is a thousandth of an inch) thick, compared with the 5.5 mils thickness that is standard for acetate safety film. The cost of shipping film and the amount of storage space required are both reduced. More significant to the projectionist than shipping cost is the fact that this increased footage per reel will make for fewer changeovers per show. Probably the most important charac teristic of Cronar from the projectionist's point of view is its toughness. In laboratory tests using a 6-foot loop of Cronar film, it was found to endure 3,000 runs through a standard 35-mm projector under normal operating conditions with little sign of wear afterwards. A loop of acetate film withstood 1150 runs under the same circumstances. Both laboratory and field tests were conducted by the Du Pont Co., and the results were described in a paper read by Dr. Deane R. White, of Du Pont, at the Fall convention of the Society of Motion Picture and Television Engineers. The paper was written by Dr. White in conjunction with C. J. Gass, E. Meschter and Wilton R. Holm, all of Du Pont. Except for one case of equipment failure (the take-up belt broke), reels containing Cronar film were run for more than 300 times in the field tests conducted last Spring without any film breakage whatever, even in the leaders, according to the paper read before the SMPTE. "No perforations bioke out, and no repair splices had to be made on the polyester reels," il was said. Leaders of cellulose triacetate film, used for comparison tests in the same theatres, had to be re placed twice or more often before 300 runs had been completed. Focus Difficulties The field tests turned up only one difficulty, it was reported, a tendency of the 4-mil Cronar base to be difficult to focus in some projectors. "Additional high-intensity projection studies are now in progress, and it is expected that evaluation tests in the near future will demonstrate freedom from focus troubles," it was predicted by Dr. White. Two typical comments from projectionists who helped to test Cronar film in the field follow. Although reported independently and not incorporated in the paper read by Dr. White, these comments are in agreement with his findings. "This film is very pliable and extremely difficult to break or tear by hand even if folded double," states Jules Margules of the Criterion Theatre, New York City. "Since it is slightly thinner than ordinary stock, you can put about 1,350 feet on a 1,000foot reel. There is a certain resiliency to the film so that even the pull on the sprocket holes when the motor is started does not undercut or break the film. At the end of the test run, the leaders were not broken nor in need of any patches. We find it to be a big step in the advancement of our industry." The focus problem was noted by Ted Pylet, of the Hawaii Theatre in Hollywood. "I ran the test film for one 12-hour shift and found it to have a tendency to go in-and-out of focus," he said. "This I believe was due to 2 FRAMES \///S////////////.//////////A 2 FRAMES NOT CEMENTED z zzzzzzzzz A w-y j /'//>'/'/)/ y >// \ This is how extremely thin, adhesive-coated tape is used in splicing where Cronar film is involved. (A) is a butt splice and (B) a lap splice. Since no cementing or welding of the two ends to be joined takes place, Cronar can be joined to itself or1 to any other film base despite the difference in the chemical nature of the ends to be joined. The "Mylar" tape used for the splicing was also developed by Du Pont. This tape with its adhesive coating1 is only 1.5 mils, or 1.5 thousandths of an inch, thick. 16 INTERNATIONAL PROJECTIONIST NOVEMBER 1955