Glassy faience from the Hallstatt C period in Poland: a chemico-physical study.

Beads and pin heads made of glassy faience , often decorated with true glass , discovered at seven different cemetery sites in Poland and dated chiefly to the Hallstatt C period (c. 750/700–600 BC), were examined by the LA-ICPMS and EPMA methods. The analysis involved 48 samples from 39 objects. The main objectives were: (i) to characterize the glassy faience in terms of the physical structure and chemical composition of the glass; (ii) to evaluate differences in the chemical composition of the glass forming the glassy faience; (iii) to examine the chemical composition of the true glass in the decoration on objects made of glassy faience. Glassy faience was found to be made of glass and numerous quartz grains, inclusions and gas bubbles. Manifest in the true glass of the decoration were numerous minor inclusions of the colorant, represented mostly by a compound of lead and antimony. Two groups of glass forming glassy faience were distinguished based on the differences in chemical composition: LMMK and LMGGF. The first is characterized by a moderate concentration of K2O (average 2.7%), high Al2O3, Fe2O3 and some trace elements (e.g. B and Ti). The second has a generally lower content, compared to LMMK, of K2O, Na2O, Al2O3, Fe2O3, B2O3 and TiO2, but higher PbO and Sb2O5. True glass LMG contained little K2O, Al2O3, B2O3 and TiO2, but a large amount of PbO and Sb2O5. All of the glasses had a low content of CaO and MgO. LMMK glass was melted using sand and a flux that could not be easily identified (plant ash?), whereas LMGGF and LMG glass used sand and natron. The glassy faience is usually blue and was colored with cobalt compounds. The yellow glass of the decoration was colored with lead antimonate. [ABSTRACT FROM AUTHOR]