What is the act or process of imparting to caoutchouc, gutta-percha, or the like, greater elasticity, durability, or hardness by heating with sulphur under pressure called?

vulcanization — The act or process of imparting to caoutchouc, gutta-percha, or the like, greater elasticity, durability, or hardness by heating with sulphur under pressure. (Webster's 1913.)

Sources