Fouque411 showed that the azure-blue color of the pigment was due to the presence of a single crystalline compound, a calcium copper silicate having the composition represented by the formula CaCuSi4Oi0. Fouque was able to reproduce this pigment, but it was not until 1914 that the exact conditions necessary for its formation were determined by the detailed experiments of Laurie, McLintock, and Miles.412 An account of its manufacture given by Vitruvius413 indicates the general procedure that the ancients followed in making it.
Though blue frit undoubtedly originated in Egypt and was much used there, its use was actually very widespread, for many examples of the pigment have been found in nearly all the principal centers of ancient civilization bordering on the Mediterranean. Its use in Greece at the time of Theophrastus is certain; in the excavations at Athens specimens have been found both of the pigment itself and of objects colored with it ranging in date from the sixth or fifth century b.c. down into the Roman period.414 It seems unlikely, however, as is implied by the statements of Theophrastus, that this pigment was manufactured outside Egypt until a comparatively late date. Vitruvius415 states that the methods of making it were first discovered at Alexandria. This must be incorrect, since Alexandria was founded many centuries after blue frit was first known. He adds that Vestorius afterwards began to manufacture it at Puteoli, and it may well be that this was the place where it was first manufactured outside Egypt.
55. those who write the history of the kings of Egypt state which king it was who first made fused kyanos in imitation of the natural kind; and they add that kyanos was sent as tribute from Phoenicia and as gifts from other
411 F. Fouque, Comptes Rendus Hebdomadaires des Seances de VAcademie des Sciences (Paris), CV1II (1889), 325.
412 A.P. Laurie, W.F.P. McLintock, and F.D. Miles, Proceedings of the Royal Society of London, LXXXIX-A (1914), 418-29.
413 Vn, 11, 1.
414 E. R. Caley, Hesperia, XIV (1945), 152-56.
415 VII, 11, 1.
