Vulcanization is a chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulfur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains. Vulcanized materials are less sticky and have superior mechanical properties. The term vulcanized fibre refers to cellulose that has been treated in a zinc chloride solution to cross-link the cellulose fibers. Although the curing of rubber has been carried out since prehistoric times, the modern process of vulcanization, named after Vulcan, the Roman god of fire, was not developed until the 19th century, mainly by Charles Goodyear. Today, a vast array of products are made with vulcanized rubber including tires, shoe soles, hoses, and conveyor belts. Hard vulcanized rubber is sometimes sold under the brand names ebonite or vulcanite, and is used in making articles such as clarinet and saxophone mouth pieces, bowling balls and hockey pucks.