put in paper containers for the market. Variations in this largescale process also occur. In some factories, copper turnings are mixed with the fermented marc and, after the reaction has taken place, the verdigris is separated from the copper that remains. The process is also conducted on a small scale by methods which probably differ very little from those employed in ancient times. The blue verdigris produced by this so-called French process consists chiefly of monobasic copper acetate, Cu(C2H302)2.Cu(OH)2. 5H2O.
Theophrastus, like Vitruvius,442 lists verdigris among the pigments, but Pliny nowhere mentions the use of it in his discussion of painting. Although verdigris has never been found in modern investigations of ancient pigments, this is no proof that it was not used as a pigment. Since basic copper acetate is not a very stable compound, any pigment composed of it would probably have changed completely in the course of the centuries to some more stable copper compound such as the basic carbonate. But the Stockholm Papyrus provides definite evidence of the use of verdigris as a coloring material and lists it as an ingredient in many of the recipes for the preparation of imitation gems. The statements of Pliny443 indicate that the compound was used extensively by the ancients in the preparation of various remedies.
58. There is also a natural and a prepared kind of cinnabar.
Theophrastus has previously shown that the blue pigments and the red iron oxide pigments are both natural and artificial. He seems to think that there are also two kinds of cinnabar, though all the available evidence indicates that this pigment was not produced artificially by the ancients. The earliest mention of the artificial preparation of cinnabar occurs in certain technical recipe books of the Middle Ages.444 The subsequent statements of Theophrastus in this section show clearly that the real difference between the two kinds was in their mode of occurrence: in some places cinnabar was found in a pure enough state to be used directly, but in others it was mixed with extraneous matter from
"2Vn, 12, 1.
««XXXIV, 113-15.
·*** Stillman, The Story of Early Chemistry, p. 186.
