Production technology and replication of lead antimonate yellow glass from New Kingdom Egypt and the Roman Empire

Lead antimonate was used to produce opaque yellow glasses from the beginnings of glass production in the Near East and Egypt around 1500 BC through into the Roman period. The composition and crystallographic structure of lead antimonate particles present in a small group of New Kingdom Egyptian and Roman glasses were investigated using analytical scanning electron microscopy and X-ray diffraction. The results showed that the particles were of the type Pb2Sb2O7 with a cubic structure and with the antimony partially replaced by iron and zinc in the case of the Egyptian glass, and by iron and tin in the case of the Roman glass. Synthesis in the laboratory of lead antimonate pigments, animes (i.e., lead-antimony-silica mixtures) and yellow glasses established that New Kingdom Egyptian and Roman yellow glasses could have been produced by stirring, respectively, lead antimonate pigment or anime, containing excess lead oxide, into a molten colourless glass. It is further shown that yellow lead antimonate particles are stable in glass up to operating temperatures in the range 900-1000 °C before converting to white calcium antimonate, and that their stability is enhanced by incorporating small amount of impurities such as iron, zinc and tin. The effect of different synthesis parameters and compositions on the colour of the glasses is investigated using UV-vis reflectance spectrometry.