American cinematographer (Jan-Dec 1955)

TOUGHEST, THINNEST FILM . • • Du Pont’s new Cronar polyester film base, now in production and soon to be made available in motion picture negative and positive films, holds many benefits for the motion picture industry. Thinner, tougher, and out-performing present cellulose triacetate film base in many ways is Cronar — new poly¬ ester film base developed by Du Pont. Cronar, brother of Mylar polyester film and half-brother to Dacron polyester fiber, is at least two times stronger than conventional film bases. In the realm of motion pictures, the film promises more durability, improved optical quality, and chemical and dimensional stability. It promises the industry a film base that will not break as easily as today’s motion picture film. A six-foot loop of Cronar base showed virtually no sign of perforation failure after more than 3,000 projections, while the film base now in use failed after 1.500 projections. Tests at Du Pont’s Photo Products Research Laboratory showed that Cronar base could be flexed more than 15.000 times before breaking. Present film base on the other hand, broke after forty flexings. Cronar is destined to be the film base of the future, sup¬ planting the present triacetate film. Early last month the Du Pont Company announced that it had licensed Eastman Kodak Company to manufacture polyester photographic base and film under Du Pont patents. The license, which is non-exclusive and non-transferable, grants Eastman and its subsidiaries the right to make polyester film base and use it in making photographic film. Du Pont has been producing pilot plant quantities of Cronar for the past three years and is currently starting up a large-scale unit to manufacture the new base at its Parlin, N. J., plant where existing facilities will be used to convert it into finished photographic film. Du Pont has given its AT PRESENT, splicing of Cronar film is by means of adhesive Mylar tape, as demonstrated here by DuPont's Wilton R. Holm (center). Alternative splicing techniques are in final stages of development and will be announced prior to full com¬ mercialization of Cronar film. polyester base and the photographic film made therefrom the trademark, Cronar. Dr. Deane R. White, at the opening session of the Society of Motion Picture and Television Engineers at Lake Placid Club, New York, last month read a paper on the subject of this new film base which he had prepared in collabora¬ tion with Charles J. Gass, Emery Mescbter and \K ilton R. Holm. Among other things the paper points out that very early in the development program of this new film base it be¬ came apparent that, because of the outstanding strength and durability of polyester base, it might be feasible to reduce the thickness of motion picture film support signifi¬ cantly below the 5.5 mil standard thickness used for pres¬ ent film bases. “A survey was made within the industry,” the paper states, “and the consensus was that such a reduc¬ tion in film thickness would be desirable since it would re¬ sult in such economic and film-handling advantages as more footage per reel, fewer reels and containers, and less shipping weight per picture. Early experiments led to the conclusion that a 4 mil polyester base would give satis¬ factory performance. All data accumulated to date indicates that satisfactory film structures can be made with 4 mil base. Actually, for 16mm film, still thinner base appears 646 American Cinematographer November, 1955