Government discovers method to preseve film. Folding endurance test, The flexibility is measured in this folding endurance tester. A strip of film is folded back and forth under tension until it breaks, and the number of folds it withstands is counted. Three types of films have been studied, termed accoring to the chemical process of making them, acetate, viscose, and nitrate. The acetate base proved to be very stable on heating and is considered suitable for permanent records if properly made. The nitrate base became brittle quite raipidly and is considered unsuited for record purposes. The viscose base is in an intermediate position similar to that of record papers made from ordinary bleach wood fiber, 7/8/38