Ebonite is a very hard rubber first obtained by Charles Goodyear by vulcanizing rubber for prolonged periods. It is about 30% to 40% sulfur. Its name comes from its intended use as an artificial substitute for ebony wood. Ebonite is a brand name — it is also known as vulcanite or hard rubber.
It is often used in bowling balls, smoking pipe mouthpieces, fountain pen nib feeds, and saxophone and clarinet mouthpieces. Hard rubber is also often seen as the wheel material in casters. It is also commonly used in physics classrooms to demonstrate static electricity. Hard rubber was used in the cases of automobile batteries for years, thus establishing black as their traditional color even long after stronger modern plastics were substituted.