Editing Celluloid (section)

==Environmental hazards==

===Deterioration===
[[File:A Fungi damaged photographic slide.tif|thumb|A fungus-damaged photographic slide]]
Many sources of deterioration in celluloid exist, such as thermal, chemical, photochemical, and physical.  The most inherent flaw is as celluloid ages, the camphor molecules are ‘squeezed’ out of the mass due to the unsustainable pressure used in the production. That pressure causes the nitrocellulose molecules to bind back to each other or crystallize, and this results in the camphor molecules being shoved out of the material. Once exposed to the environment, camphor can undergo [[Sublimation (phase transition)|sublimation]] at room temperature, and the plastic reverts to brittle nitrocellulose. Also, with exposure to excess heat, the nitrate groups can break off and expose nitrogen gases, such as [[nitrous oxide]] and [[nitric oxide]],<ref>Springate, Megan E. (1997) "Cellulose Nitrate Plastic (Celluloid) in Archaeological Assemblages: Identification and Care,"Northeast Historical Archaeology: Vol. 26 26: Iss. 1, Article 5.
</ref> to the air.

Another factor that can cause this is excess moisture, which can accelerate deterioration of nitrocellulose with the presence of nitrate groups, either newly fragmented from heat or still trapped as a free acid from production. Both of these sources allow the accumulation of nitric acid. Another form of deterioration, photochemical deterioration, is severe in celluloid because it absorbs [[ultraviolet]] light well. The absorbed light leads to chain-breakage and stiffening.<ref name="cool.conservation-us.org"/>

Among collectors of antiques, the deterioration of celluloid is generally known as "celluloid rot." The chemical processes involved are not perfectly understood, but it is widely believed that the gases released by a piece undergoing celluloid rot can trigger celluloid rot in nearby articles of celluloid which were previously intact.<ref>{{Cite web|url=https://acousticguitar.com/ask-the-expert-all-about-celluloid-rot-and-what-to-do-about-it/|title=Ask the Expert: All About Celluloid Rot—and What to do About It &#124; Acoustic Guitar|date=9 September 2021}}</ref>