Cellulose Nitrate (Extra)

This will be my final blog on materials we may use or encounter in the workshop...so enjoy!

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The plastic cellulose nitrate was invented in the early 19^th century, and is often thought of as the earliest synthetic polymer or plastic. The uses of cellulose nitrate range from everything including cutlery handles, toys and dolls, photographic film, and many other cosmetic, household and toiletry items. It was even used by Kodak, and other suppliers, from the late 1880s as a film base in photograph, X-ray films and motion picture films; and was known as nitrate film. After numerous fires caused by unstable nitrate films, safety film started to be used from the 1930s in the case of X-ray stock and from 1948 for motion picture film.The colour of an untouched, unprocessed cellulose nitrate plastic is transparent and colourless, and until about the 1920, the only cellular nitrate plastic available was light coloured or translucent.

An old, rusted, rolled up film reel made from Cellulose Nitrate

The stability of cellulose nitrate is strongly influenced by the amount of nitrogen present, the more nitrogen content, the more unstable the product. Therefore, products with high nitrogen content (usually more than 13%) are likely to explode on contact to heat, friction, or shock, whereas objects with a lower nitrogen content (typically less than 12%) are not explosive.

There were two main types of Cellulose Nitrate Guncotton and Nitrate Film: 

Guncotton:

In general, cotton was used as the cellulose base, and is added to concentrated sulphuric acid and 70% nitric acid cooled to 0 °C to give cellulose trinitrate (or guncotton).

While guncotton is dangerous to store, its risks can be reduced by storing it wet or in oil.

Nitrate Film:

Cellulose is treated with sulfuric acid and potassium nitrate to give cellulose mononitrate. This was used commercially as Celluloid, a highly flammable plastic used in the first half of the 20th Century for lacquers and photographic film.

However, cellulose nitrate degrades to produce acidic and oxidizing nitrogen oxide gas. In enclosed spaces with restricted ventilation, these gases can build up, causing metal to erode, and discolour organic materials, as well as accelerate the process at which objects decay. Cellulose nitrate is additionally a very flammable material and must be isolated from heat and ignition sources.

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                                  Thank you very much for reading my post on Cellulose Nitrate.

                                                 Next up, will be a post on Sustainability!