Acetate Film Base Beginning in the mid-1920s, highly flammable nitrate film was slowly replaced with cellulose acetate film base (cellulose diacetate, cellulose acetate propiarate, cellulose acetate butyrate and cellulose triacetate). It became known as "Safety" film. Despite this name, cellulose acetates do have stability problems. Like cellulose nitrate, the deterioration of cellulose acetate is autocatalytic: once deterioration has begun, the degradation products induce further deterioration. It affects the plastic support of acetate film, causing it to become acidic, to shrink, and to give off of acetic acid producing a vinegary odor. A useful tool in helping determine the amount of acid vapor present, and gain an overview of the condition of acid vapors in an entire collection are "A-D Strips" (acid-detecting strips). They are acid-base indicator papers, which turn from blue to green to yellow in the presence of acid, and measure the extent of the acetate bas
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