a brand name for a material generically known as hard rubber, and is obtained by vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as an artificial substitute for ebony wood.
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Hard rubber was used in early 20th century bowling balls; however, it was phased out in favor of other materials (the Ebonite name remains as a trade name for one of the major manufacturers of polymer balls). It has been used in electric plugs, tobacco pipe mouthpieces (in competition with Lucite), hockey pucks, fountain pen bodies and nib feeds, and saxophone and clarinet mouthpieces as well as complete humidity-stable clarinets. Hard rubber is often seen as the wheel material in casters
detached the plug of the electric lamp by his bed, and picked it up winding the flex round it. It was a chromium affair with a heavy ebonite base—a useful weapon
Agatha Christie. And Then There Were None. p.160 (1939)