Caput mortuum
Composition and Properties of Caput Mortuum
Caput mortuum is either a relatively modern synthetically prepared iron(III)-oxide, but the name has also been used for natural hematite-containing material treated with heat which was found in antique and medieval paintings. The color can vary from dark brown to black-violet depending mainly on particle size.Iron oxides are stable at high temperatures but not resistant against acids, it is, however, absolutely lightfast.
Names
Venetian red, colcothar, Spanish brown, Falun red, burnt vitriolPR 101From Latin caput mortuum meaning death’s head. The name goes back to the alchemists who used it for the ultimate remains of an alchemical process signifying something not changeable and thus worthless.
Preparation
This iron oxide pigment can be prepared by calcinating (heating) iron sulfate.
History of Use
Recipes for the preparation of the pigment known as colcothar have been found in various medieval alchemist manuscripts.
Quote
I conceive it is a vulgar error in translating poets, to affect being fidus interpres... [for] poetry is of so subtile a spirit, that in the pouring out of one language into another, it will all evaporate; and if a new spirit be not added in the transfusion, there will remain nothing but a caput mortuum, there being certain graces and happinesses peculiar to every language, which give life and energy to the words... therefore if Virgil must needs speak English, it were fit he should speak not only as a man of this nation, but as man of this age. The Destruction of Troy (1656), Preface
Source: John Denham
The strata of fossil coal are found in almost every intermediate state, as well as in those of bitumen and charcoal. Of the one kind is that fossil coal which melts or becomes fluid upon receiving heat; of the other, is that species of coal, found both in Wales and Scotland, which is perfectly infusible in the fire, and burns like coaks, without flame or smoak. The one species abounds in oily matter, the other has been distilled by heat, until it has become a caput mortuum, or perfect coal.
Source: Theory of the Earth
