211-255

Workshop for the manufacture of pigments in the ancient agora of Kos

Σύμμεικτα

• Καντζιά, Χάρις
• Κουζέλη, Καλλιόπη

A. THE EXCAVATION The remains of a late Hellenistic workshop for the preparation of pigments, using metals as the raw materials, were discovered in 1987 in a room on the east side of the Hellenistic Agora on Cos. The south part of the Agora has been recently excavated in the building plot belonging to the Damtsas brothers in Vy- ronos, Meropidos and Peisandrou Streets in the town of Kos. Along a low wall the remains were found of three hearths and a collapsed kiln made of clay bricks. The large quantify of «tubed» litharge (some 50 rods) and the many lumps of smelted lead, chiefly in the shape of drops, that were found in the area of the kiln, lead to the supposition that the kiln was used for the reduction of litharge and the production of lead. The main product of the workshop was Egyptian blue (Pompeianum or Ve- storium blue), of which a considerable quantity was found in the form of small balls the size of a walnut among the remains of intense burning in the west hearth. Pine branches and cones had been used as fuel in ths hearth, where some 90 pellets of Egyptian blue were found.Egyptian blue, a combination of copper, silicon, lime and oxygen (CuCa- S14O10), known as blue frit, is a synthetic pigment that was probably invented in Egypt at the beginning of the 3rd millennium BC and was used in the Mediterranean in antiquity, chiefly for frescopainting. It is produced by heating a mixture of siliceous sand, copper, carbonate of lime and nitric salts to a temperature of 84ÔC. Vitruvius (VII. 11) describes the method of established by Vestorius at Puteoli in Italy. A considerable amount of Eguptian blue in the form of pellets and powder that was found at Pompeii is thought to have been imported fromB. THE CHEMICAL STUDY K. KOUZELIIn this study the chemical composition and microstructure of samples of Egyptian blue from the excavation in the Damtsas building-plot on Kos are examined, as well as samples of the by-products from its preparation. The techniques chiefly used were atomic absorption spectroscopy, X-ray diffraction spectroscopy, electron microscopy and mirco- probe analysis. The samples of successfully made Egyptian blue have a significant excess of silica and are rich in alkalis. Their calcium oxide content appears to be rather low. In the samples ofPuteoli.In the Kos workshop, which is perhaps the only one of its kind hitherto known other colouring substances were also found in smaller quantities: red, brown, purple, yellow and pink pigments.B. THE CHEMICAL STUDYIn this study the chemical composition and microstructure of samples of Egyptian blue from the excavation in the Damtsas building-plot on Kos are examined, as well as samples of the by-products from its preparation. The techniques chiefly used were atomic absorption spectroscopy, X-ray diffraction spectroscopy, electron microscopy and mirco- probe analysis. The samples of successfully made Egyptian blue have a significant excess of silica and are rich in alkalis. Their calcium oxide content appears to be rather low. In the samples ofPuteoli.In the Kos workshop, which is perhaps the only one of its kind hitherto known other colouring substances were also found in smaller quantities: red, brown, purple, yellow and pink pigments.unsuccessful Egyptian blue some green areas were observed in which quartz, christobalite and wollastonite were detected, and some dark areas in which, apart from quartz and christobalite, the formation of Egyptian blue had also begun.Production of Egyptian blue was also carried out in the laboratory and yielded some conclusions about the factors that may determine the course of the reaction (grain size of the raw materials, temperature, iron oxide content).

• History and Archaeology

• Ανασκαφές (Αρχαιολογία)

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