vulcanise

Verb

vulcanize (third-person singular simple present vulcanizes, present participle vulcanizing, simple past and past participle vulcanized)

1. (transitive) To treat rubber with heat and (usually) sulfur to harden it and make it more durable.
   • Local workers hike up the side of the mountain and down into the crater at the top to harvest its sulfur—a byproduct of the gas that escapes from the volcano’s vents and collects near the shores of an acidic lake at the crater’s center. The chemical is used in industry worldwide, from making...2015 February 25, Kevin McElvaney, “Inside Indonesia's Ijen Volcano”, in The Atlantic, archived from the original on 06 Mar 2016
2. (intransitive) To undergo such treatment.
   • These vulcanized hearts, they only become more resistant when you ask for mercy.1976 September, Saul Bellow, Humboldt’s Gift, New York, N.Y.: Avon Books, →ISBN, page 404