What is "fumage"

Fumage \Fu"mage\, n. [OF. fumage, fumaige, fr. L. fumus smoke.] Hearth money.

Fumage, or fuage, vulgarly called smoke farthings.
--Blackstone.

n. hearth tax

Fumage is a surrealist art technique popularized by Wolfgang Paalen in which impressions are made by the smoke of a candle or kerosene lamp on a piece of paper or canvas. Salvador Dalí later utilized the technique in his paintings, calling the technique "sfumato". The technique has been utilized by several artists such as Yves Klein, Burhan Doğançay, Jiri Georg Dokoupil, Otto Piene, Antonio Muñiz, Bimal Banerjee, Hugh Parker Guiler, Steven Spazuk and Adam Blakemore.