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The most common type of celluloid degradation is caused by camphor gradually working its way out of the product. Extreme heat will contribute to this process. This causes embrittlement, and in transparent or translucent items deep crazing will be evident. Items affected this way will crumble completely.
More serious degradation occurs when the nitrocellulose degrades, giving off oxides of nitrogen. These combine with water, usually also present when this reaction takes place, forming nitric acid. This is very corrosive to metal, fabric, paper, etc., and often results in substantial destruction of surrounding materials. The effects are worse when the celluloid products are stored in closed containers. The fumes are more concentrated, and the by-products catalyze further reaction, leading to further damage.
People often wonder whether anything can be done to treat celluloid buttons or other products to prevent these types of degradation. Proper storage, in ventilated containers, without excess humidity or high temperatures, will make degradation less likely. Unfortunately, once it has begun it is impossible to reverse. Many celluloid items are stable, but unfortunately it is not possible to know which these will be, although translucent and transparent celluloids are more prone to degradation initiated by ultraviolet light. (Colouring agents which prevent light transmission through celluloid objects appear to give some protection.) Most factors which make degradation likely are present from the time of manufacture, and only proper storage can minimize their effects. Some of these factors include: the purity of ingredient materials; the rinsing and drying processes, which may leave agents catalyzing degradation in the finished materials; the kneading process, which affects the celluloid structure; stability of added materials; and other manufacturing processes.
Celluloid must be stored in ventilated containers, protected from light and humidity. It must be kept separately from other materials, particularly metals, which are attacked by corrosive products of celluloid degradation. Celluloid buttons should be examined periodically and any showing signs of degradation, or affecting surrounding materials, should be discarded. On the bright side, many celluloid buttons have been around for 100 years without showing any signs of degradation, and with proper storage most will stay sound.