What is celluloid?
(And why is it not the same as cellulose nitrate/nitrocellulose?)
Celluloid is usually cited as the first synthetic plastic. Its origins go back as far as the 1850s, but as a commercial product it is to be dated to the 1860s, with successful large-scale manufacture being more a development of the 1870s. It was only in the 1920s, however, that fountain pen makers wholeheartedly embraced the material. Unlike hard rubber, celluloid could be made in a huge range of colors and patterns, simulating almost any natural material imaginable. Although some cheap pens were made of molded celluloid, nearly all better pens were made of rod or plugged tube stock that was machined to shape.
Although the main ingredient of celluloid is nitrated cellulose, celluloid and cellulose nitrate (also known as nitrocellulose) are not the same. To make celluloid, cellulose nitrate must be plasticized with camphor, celluloid's other essential component.
In the modern world, true celluloid is almost extinct. Much of the colorful "celluloid" used in contemporary pens, eyeglass frames, and fashion accessories comes out of Italy, but it is in fact based on other forms of cellulose -- cellulose acetate, in particular. The manufacture of true celluloid is fairly hazardous, and many old-time factories were destroyed by fire. Although the nitration level of cellulose nitrate intended for celluloid rod and tube is much less than that used for celluloid film or the nitrocellulose used in gunpowder, it is still a highly inflammable substance, worked in turn using inflammable solvents.