Webster's Revised Unabridged Dictionary · 1913

Whiten

Whiten , intransitive verb

[Old English whitenen; compare Icelandic hvītna.]

To grow white; to turn or become white or whiter; as, the hair whitens with age; the sea whitens with foam; the trees in spring whiten with blossoms.

Whiten , transitive verb

To make white; to bleach; to blanch; to whitewash; as, to whiten a wall; to whiten cloth.
The broad stream of the Foyle then whitened by vast flocks of wild swans. — Macaulay