Answer: annealer

AnswerCrossword Clue
ANNEALERGlassworker, at times
ANNEALEROven for tempering glass.
ANNEALERTempering agent.
ANNEALEROne working with glass, at times
annealerto toughen or temper (metal or glass)
annealerone who anneals (to toughen (to make tough))