Abstract
Portuguese archaeological excavations dated to the 17th century onwards are extremely rich in glass artefacts, with this being a reality from the north to the south of the territory. Contrasting with this reality, no glass production locations from this period have been discovered or excavated so far, which makes the provenance attribution a challenging endeavour. One specific archaeological location, the Monastery of Santa Clara-a-Velha in Coimbra, held one of the largest glass archaeological assemblages dated to the 17th century unearthed in Portugal so far. Due to the large variety of objects’ shapes, glass colours and decorative features, this assemblage is a valuable candidate to hold glass artefacts produced in Portugal. Lacking archaeological excavation on glass furnaces in Portugal, the study of glassmaking raw materials is the most promising research line to investigate the provenance of glass circulating in Portugal. In this study, sand and pebbles from six different locations in the north/centre of Portugal were collected and melted to produce glass samples. The resulting glass samples were chemically characterised using LA-ICP-MS, to obtain the composition of the samples in major, minor and trace elements. The obtained results were compared with the composition of 37 historical samples from the Monastery of Santa Clara-a-Velha previously studied. Additionally, the thermal properties of selected synthesised glasses were analysed by Differential Scanning Calorimetry, allowing new insights on melting temperatures and glass workability. Results indicate that three artefacts with stylistic features attributed to a Portuguese production were locally made with sands collected in Coimbra.
Highlights
In the last few decades, the study of historical glass concerning its provenance, origin and nature of the employed raw materials has experienced considerable evolution
Portuguese archaeological excavations dated to the 17th century onwards are extremely rich in glass artefacts, with this being a reality from the north to the south of the territory
The Monastery of Santa Clara-a-Velha in Coimbra, held one of the largest glass archaeological assemblages dated to the 17th century unearthed in Portugal so far
Summary
In the last few decades, the study of historical glass concerning its provenance, origin and nature of the employed raw materials has experienced considerable evolution. Natural sand results from the accumulation of mineral quartz of high insolubility that is composed, by silica, and by other insoluble minerals All these minerals constitute the composition of the glass. These secondary minerals bring to the glass variable contents of aluminium, iron, titanium, zirconium and rare earth, among others, that differ from one sand deposit to another depending on Minerals 2022, 12, 193 nium and rare earth, among others, that differ from one sand deposit to another depending on the type of rock source [3,4]. Historical Background—the Glass from the Monastery of Santa Clara-a-Velha as a CaseStHudisytorical Background—The Glass from the Monastery of Santa Clara-a-Velha as a Case-Study
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