cendrar

An archaic, literary metallurgical verb meaning to refine or purify a metal (especially gold or silver) by removing dross with ash (cendra): el oro se cendraba para eliminar impurezas. Older literary Spanish also used it figuratively for purifying something abstract, like character or style. A verb met only in older texts or specialized historical writing, never modern conversation.

• Los orfebres cendraban el oro antes de trabajarlo. — Goldsmiths refined the gold with ash before working it.
• En textos clásicos, cendrar el alma significaba purificarla de vicios. — In classical texts, to 'cendrar' the soul meant to purify it of vices.
• El proceso de cendrar la plata requería calor y cenizas especiales. — The process of refining silver required heat and special ashes.

Treating cendrar as a common synonym for purificar or refinar — it's a specialized, archaic term almost exclusively tied to historical metallurgy; modern Spanish just says purificar or refinar.