How safe is expired film?
Using "expired" film All undeveloped films change over time, losing contrast and color balance. This is a gradual chemical reaction, the rate of which is a function primarily of storage conditions. High storage temperatures accelerate change; low temperatures slow it; freezing stops it. Humidity accelerates it; dry storage helps minimize it. Most film is sold in retail stores, which do not use refrigeration. For that reason, film factories print "process before" dates on their packages. The practice dates from the end of the 19th century, when air conditioning was unknown and refrigeration was uncommon. The factory "process before" date for film is, typically, two years from the month in which the film was packaged. This is always conservative, because the factory must assume that film on retail shelves is stored relatively warm. The "process before" date of fi