This article is about a purple pigment. For the brown pigment, see
Mummy brown.
Caput mortuum (
Latin for 'dead head', and variously spelled caput mortum or caput mortem), also known as cardinal purple, is the name given to a purple variety of
haematiteiron oxide pigment, used in
oil paints and paper
dyes. Due to the cultural significance of its deep purple colour, it was very popular for painting the robes of religious figures and important personages (e.g. art patrons), with its popularity peaking in the 18th and 19th centuries.[1][2]
The name for this pigment may have come from the alchemical usage, since iron oxide (rust) is the useless residue (caput mortuum) of oxidization. It was originally a byproduct of
sulfuric acid manufacture during the 17th and 18th centuries, and was possibly an early form of the
copperas process used for the manufacture of
Venetian red and
copperas red.[3][4]