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Reinventing the Celluloid Tortoise

Reinventing the Celluloid Tortoise

by Henry Stocek

Originally published in American Lutherie #61, 2000 and Big Red Book of American Lutherie Volume Six, 2013

Celluloid is a dinosaur, and making it is a disappearing art. Only musical instruments and ping-pong balls require it anymore. Yet it is the only plastic that can resemble organic materials, have a beautiful depth in its look, and be sliced into thin sheets that remain stable. Acetates and resins still cannot achieve the look and remain stable at the thicknesses required for pickguards.

Its composition is very simple: cellulose soaked in a nitric acid solution and plasticized with camphor. Cellulose is derived from the cell walls of any plant. Cotton used to be the source of the cellulose used to make celluloid, but I think wood is the main source today because it’s the cheapest. In 1846, it was discovered that if cotton was soaked in a nitric acid solution, they got nitrocellulose. With a lot of nitric acid, it becomes an explosive — gun cotton. The Navy shoots big guns with this even today. With a less acidic application, the nitrocellulose is a nonexplosive stuff that can be molded into solid shapes, although it is very brittle. About 1860, John Wesley Hyatt accidentally discovered that by adding camphor, an aromatic paste from an Asian tree (think Vicks and mothballs), the nitrocellulose became a moldable solid that did not get brittle. Hence, celluloid. Today, solvents like acetone and alcohol are used to blend it. It’s cooked under pressure once the color composition has been established. It is an approximate science — more art and intuition than exactness. Hence the difficulty in achieving a tortoise pattern and color that come out right.

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