Abstract
AbstractThe subject of this study consists of 17 ancient glass fragments from the island of Ustica (Palermo, Italy) obtained from local museums. All the 17 glass fragments are stratigraphically decontextualized, as they were collected by archaeological surface surveys. Each fragment was analyzed by Electron Micro Probe Analyzer coupled with an Energy Dispersive X-Ray System (EMPA-EDS) and by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to obtain the composition of major, minor and trace elements. Surface analyses revealed the presence of corrosion layers in most of the glass fragments which was evident also in the chemical data. Nevertheless, reconstruction of the glassmaking processes and the approximate period of production was possible for almost all the glass fragments. Less than half of the examined fragments are attributable to recognizable typologies as unguentaria, beakers, bottles, and vases; all the other small fragments are typologically undetermined. Out of 17 fragments only one fragment is of HLLA composition possibly being produced in 17th–18th century AD, while all the others can be attributed to soda glass with different periods of production: natron glass from Roman and Early Medieval period, plant-ash glass from High or Late Medieval period with the exception of possible Byzantine glass from 6th century AD, and synthetic soda glasses typical of modern era. These data confirm the discontinuous habitation of the island from the Roman period as well as the import of glass objects to the island.
Highlights
This work provides the first archaeometric study of ancient glass fragments found in Ustica
Out of 17 fragments only one fragment is of high lime-low alkali (HLLA) composition possibly being produced in 17th–18th century AD, while all the others can be attributed to soda glass with different periods of production: natron glass from Roman and Early Medieval period, plantash glass from High or Late Medieval period with the exception of possible Byzantine glass from 6th century AD, and synthetic soda glasses typical of modern era
Nowadays we know that the typical ancient glass recipe requires mixing three fundamental components which are heated up to their melting point: a silica-based vitrifying agent (SiO2) as the lattice former; a flux based on alkaline and alkaline earth compounds (Na2O, K2O, MgO) to lower the high melting temperature of silica; and a stabilizer such as calcium oxide (CaO) to slow down the processes of glass alteration over time (e.g., Freestone, 2005; Gratuze & Janssens, 2004; Wedepohl, Simon, & Kronz, 2011; and references therein) (Figure 3)
Summary
This work provides the first archaeometric study of ancient glass fragments found in Ustica. Nowadays we know that the typical ancient glass recipe requires mixing three fundamental components which are heated up to their melting point: a silica-based vitrifying agent (SiO2) as the lattice former; a flux based on alkaline and alkaline earth compounds (Na2O, K2O, MgO) to lower the high melting temperature of silica (around 1700°C); and a stabilizer such as calcium oxide (CaO) to slow down the processes of glass alteration over time (e.g., Freestone, 2005; Gratuze & Janssens, 2004; Wedepohl, Simon, & Kronz, 2011; and references therein) (Figure 3). Legend tells that the first glass was made accidentally in ancient Phoenicia by exposing the glass ingredients to fire After this fortuitous discovery, human intelligence would have perfected glass processing in an empirical way, by trial and error, as reported by Pliny the Elder in Natural History (XXXI, 107 and XXXVI, 193–4, English edition edited by Rackham & Jones, 1962). It was possible to reconstruct, in broad terms, the technological evolution of glass production over the millennia (Wedepohl, Simon, & Kronz, 2011) (Figure 4)
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