Verbs

(v)harden, induratebecome hard or harder“The wax hardened”
(v)harden, induratemake hard or harder“The cold hardened the butter”
(v)temper, hardenharden by reheating and cooling in oil“temper steel”
(v)season, hardenmake healthy“This trip will season even the hardiest traveller”
(v)inure, harden, induratecause to accept or become hardened to; habituate“He was inured to the cold”