An evil person is like a piece of coal: if it doesn't burn, it blackens you. Anacharsis
Our disputants put me in mind of the skuttle fish, that when he is unable to extricate himself, blackens all the water about him, till he becomes invisible. Joseph Addison
I think I will go back to mahogany [wood, as layer for his paintings], the only stable wood, together with old oak. But mahogany is so heavy. And it has another drawback, it blackens even through the primers if they are not thick enough and applied in several coats. Eugène Boudin
Wearing the white flower of a blameless life, Before a thousand peering littlenesses, In that fierce light which beats upon a throne, And blackens every blot. Alfred, Lord Tennyson
Who paints me before blackens me behind. Italian Proverb
Who blackens others, does not whiten himself. German Proverb