Celluloid is a material used to make photographic and motion picture film until the late 1950s. Now, it's simply a word used to describe the classic genre of cinema. These days, films are being made out of new materials like polypropylene; celluloid is rarely used to make motion picture film anymore.
Celluloid is a class of compounds created from nitrocellulose and camphor, with added dyes and other agents. Generally considered the first thermoplastic, it was first created as Parkesine in 1856 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is easily molded and shaped, and it was first widely used as an ivory replacement.
The main use was in movie and photography film industries, which used only celluloid film stock prior to the adoption of acetate safety film in the 1950s. Celluloid is highly flammable, difficult, and expensive to produce, and no longer widely used; its most common uses today are in table tennis balls, musical instruments, and guitar picks.
Celluloid is made from a mixture of chemicals such as nitrocellulose, camphor, alcohol, as well as colorants and fillers depending on the desired product. The first step is transforming raw cellulose into nitrocellulose by conducting a nitration reaction. This is achieved by exposing the cellulose fibers to an aqueous solution of nitric acid; the hydroxyl groups (-OH) will then be replaced with nitrate groups (-ONO2) on the cellulose chain. The reaction can produce mixed products, depending on the degree of substitution of nitrogen, or the percent nitrogen content on each cellulose molecule; cellulose nitrate has 2.8 molecules of nitrogen per molecule of cellulose. It was determined that sulfuric acid was to be used as well in the reaction in order to first, catalyze the nitric acid groups so it can allow for the substitution onto the cellulose, and second, allow for the groups to easily and uniformly attach to the fibers, creating better quality nitrocellulose. The product then must be rinsed to wash away any free acids that did not react with the fibers, dried, and kneaded. During this time, a solution of 50% camphor in alcohol is added, which then changes the macromolecule structure of nitrocellulose into a homogeneous gel of nitrocellulose and camphor. The chemical structure is not well understood, but it is determined that it is one molecule of camphor for each unit of glucose. After the mixing, the mass is pressed into blocks at high pressure and then is fabricated for its specific use.
Nitrating cellulose is an extremely flammable process in which even factory explosions are not uncommon. Many western celluloid factories closed after hazardous explosions, and only two factories in China remain in business.
Most movie and photography films prior to the widespread move to acetate films in the 1950s were made of celluloid. Its high flammability was legendary since it self-explodes when exposed to temperatures over 150° C in front of a hot movie-projector beam. While celluloid film was standard for 35mm theatrical productions until around 1950, motion-picture film for amateur use, such as 16mm and 8mm film, were on acetate "safety base", at least in the US.
Celluloid was useful for creating cheaper jewelry, jewelry boxes, hair accessories, and many items that would earlier have been manufactured from ivory, horn, or other expensive animal products. It was often referred to as "Ivorine" or "French Ivory". For this use, a form of celluloid was developed in France that had lines in it to make it resemble ivory. It was also used for dressing table sets, dolls, picture frames, charms, hat pins, buttons, buckles, stringed instrument parts, accordions, fountain pens, cutlery handles, and kitchen items. The main disadvantage the material had was that it was flammable. Items made in celluloid are collectible today and increasingly rare in good condition. It was soon overtaken by Bakelite and Catalin. Table tennis balls were made from celluloid until 2014. "Parker Brothers... made some versions out of hollow Celluloid--which, because of its 'frictionless' properties, spun even faster than steel."
Shelf clocks and other furniture items were often covered with celluloid in a manner similar to veneers. This celluloid was printed to look like expensive woods or materials like marble or granite. The Seth Thomas clock company called its celluloid clock material "adamantine". Celluloid enabled clockmakers to make the typical late Victorian style of black mantel clock in such a way that the wooden case appeared to be black marble, and the various pillars and other decorative elements of the case looked like semi-precious stone.
Flaming celluloid pattern on an accordion.
Celluloid was also a popular material in the construction of slide rules. It was primarily used to coat wooden slide rule faces, such as in early A.W. Faber rules, as well as cursor end pieces, such as in Keuffel and Esser rules.
Celluloid remains in use for musical instruments, especially accordions and guitars. Celluloid is very robust and easy to mold in difficult forms and has great acoustic performance as a cover for wooden frames since it does not block wood's natural pores. Instruments covered with celluloid can easily be recognized by the material's typical nacre-like flaming pattern. Thick celluloid panels are cooked in a bain-marie which turns them into a leather-like substance. Panels are then turned on a mold and allowed to harden for as long as three months.