Molding (shaping) the rubber mixture. The rubber must be shaped prior to heating stage since cross-linking makes shaping impossible.
Heating the mixture to 250-400ºF (120-200ºC). Increased temperature speeds up the vulcanization process resulting in fast and complete cross-linking. C-S bonds replace C-H bonds linking chain polyisoprene molecules. Each link is formed by one to seven sulfur atoms.
Density of cross-links must be controlled in order to prevent formation of brittle rubber.