Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to include the hardening of other (synthetic) rubbers via various means. Examples include silicone rubber via room temperature vulcanizing and chloroprene rubber (neoprene) using metal oxides. Vulcanization can be defined as the curing of elastomers, with the terms 'vulcanization' and 'curing' sometimes used interchangeably in this context. It works by forming cross-links between sections of polymer chain which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material. Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible. The word vulcanization is derived from Vulcan, the Roman god of fire and forge. History Rubber—latex—had been known for thousands of years in Mesoamerican cultures, used to make balls, sandal soles, rubber bands, and waterproof containers. Rubber was processed for specific applications within the Aztec Empire — rubber and latex goods were processed and constructed, and then shipped to the capital for use or further distribution. Early rubber tube tires in the 19th century would grow sticky on a hot road, until debris would get stuck in them and eventually the tires would burst. Charles Goodyear, in the 1830s, was working to improve those tube tires. He tried heating up rubber in order to mix other chemicals with it. This seemed to harden and improve the rubber, though this was due to the heating itself and not the chemicals used. Not realizing this, he repeatedly ran into setbacks when his announced hardening formulas did not work consistently. One day in 1839, when trying to mix rubber with sulfur, Goodyear accidentally dropped the mixture in a hot frying pan. To his astonishment, instead of melting further or vaporizing, the rubber remained firm and, as he increased the heat, the rubber became harder. Goodyear quickly worked out a consistent system for this hardening, which he called vulcanization because of the heat involved. He obtained a patent in the same year, and by 1844 was producing the rubber on an industrial scale. Applications There are many uses for vulcanized materials, some examples of which are rubber hoses, shoe soles, toys, erasers, shock absorbers, conveyor belts, vibration mounts/dampers, insulation materials, tires, and bowling balls. Most rubber products are vulcanized