Caput mortuum

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Caput Mortuum is a Latin term meaning 'death's head'. In alchemy, it signified a useless substance left over from a chemical operation such as sublimation. Alchemists represented this residue with a stylized human skull, a literal death's head. In its current limited usage, the caput mortuum represents decline and entropy.

Caput mortuum (also spelled caput mortum or caput mortem) is the name given to a purple variety of iron oxide pigment, an "earth color". It is used in oil paints and paper dyes. The name for this pigment may have come from the alchemical usage, since iron oxide (rust) is the useless residue of oxidization.

It is the name of a browish paint that was originally made from the wrappings of Mummies. It was most popular in the 1600's. It was suddenly discontinued in the early 19th century when its composition became generally known to artists [The Artist's Handbook, p. 52]. A London colorman claimed that he could satisfy the demands of his customers for twenty years from one Egyptian mummy [The Chemistry of Paints and Painting, p. 236]. In recent years, it has been made with iron sulphate and impurities obtained from the residues of the distillation of scisti piritosi in the fabrication of sulphuric acid. The paint color is also known as Colcothar, Mummy Brown, Mummy, Egyptian Brown, and by combinations like Caput Mortem Violet.