A unique recipe for glass beads at Iron Age Sardis

Abstract

In large parts of the Mediterranean recipes for the earliest man-made glass changed from melting mixtures of crushed quartz pebbles and halophytic plant ashes in the Late Bronze Age to the use of quartz sands and mineral soda during the Early Iron Age. Not much is known about this transition and the experimental materials which would inevitably have been connected to such technological change. In this paper we present a unique snapshot of developments in glass technology in Anatolia during the Middle Iron Age, when glass is still a relatively rare commodity. The present work focusses on black glass beads decorated with yellow trails from eighth to seventh century BCE Sardis, glass beads that are very rare for this period, and on this site. A full elemental analysis of the beads was made, and Sr, Pb and B isotope ratios were determined. This study reveals the use of a combination of a previously unknown source of silica and of mineral soda, giving rise to elevated (granite-like) Sr isotope signatures, as well as high alumina and B concentrations. The yellow trails of glass on the beads consist of leadtin yellow type II, lead stannate, showing the earliest occurrence of this type of opacifier/colourant so far, predating any other findings by at least four centuries. The production of these glass beads may be local to Sardis and experimental in nature. It is therefore suggested that Sardis may have played its role in the technological development of the glass craft during the Iron Age.

Early Iron Age ‘black’ glass in Southwestern Iberia: typology, distribution, and context

“…Beads with waved line decorations are, on the other hand, rare in the Mediterranean. 'Black' and yellow examples from the Lydian capital of Sardis (Turkey) have recently been reported (Van Ham-Meert et al, 2019), which can now be added to a few blue and white examples previously known from other coastal Turkish sites (Matthäus, 1983: 64), as well as to the residual brown and white examples known from Cyprus (idem: 86). Still, the type remains rare in the Eastern Mediterranean as a whole.…”

The chemical composition and manufacturing technology of glass beads excavated from the Hetian Bizili site, Xinjiang

“…Antimony-based opacifiers were used in Late Bronze Age Egypt and Mesopotamia from the mid-second millennium BC [18], in yellow lead-antimonate and white calcium antimonate. Tin based opacifiers were introduced from the second century BC and earlier [31][32][33], and from around the fourth century AD they tended to be the dominant opacifier used in glasses in the west [34].…”

“…The earliest lead stannate has been found in a glass bead from Sardis (the eighth to the seventh century BC) [33] and in glass beads from Poland [32].…”

The chemical composition and manufacturing technology of glass beads excavated from the Hetian Bizili site, Xinjiang

“…The latest research tested lead stannate in a glass bead from Sardis (the eighth to the seventh century B.C. ), which is the earliest known occurrence of tin-based opaci ers so far [31].…”