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The ancient glass industry changed dramatically towards the end of the first millennium. The Roman glassmaking tradition of mineral soda glass was increasingly supplanted by the use of plant ash as the main fluxing agent at the turn of the ninth century CE. Defining primary production groups of plant ash glass has been a challenge due to the high variability of raw materials and the smaller scale of production. Islamic Glass in the Making advocates a large-scale archaeometric approach to the history of Islamic glassmaking to trace the developments in the production, trade and consumption of vitreous materials between the eighth and twelfth centuries and to separate the norm from the exception. It proposes compositional discriminants to distinguish regional production groups, and provides insights into the organisation of the glass industry and commerce during the early Islamic period. The interdisciplinary approach leads to a holistic understanding of the development of Islamic glass; assemblages from the early Islamic period in Mesopotamia, Central Asia, Egypt, Greater Syria and Iberia are evaluated, and placed in the larger geopolitical context. In doing so, this book fills a gap in the present literature and advances a large-scale approach to the history of Islamic glass

International audience The study of ancient and medieval glasses has identified distinct compositional groups as a result of the chemical characteristics of the raw materials used for its production. Archaeometric analysis can determine the provenance of the glass, and has demonstrated a large-scale production and commercialisation of raw glass throughout the Mediterranean during the ancient and medieval periods. Secondary workshops on the Iberian Peninsula imported raw glass from the Near East for the better part of the first millennium CE, following a similar pattern observed elsewhere in the Mediterranean region. However, there are some indications that point to a local production of glass and that deserve further investigation. In the ninth century, natron glass was replaced in al-Ándalus by plant ash and lead-rich glass that may represent a local production. Little is known about the production or use of glass in the Christian parts of the peninsula during this period.The increasing volume of analytical data on Spanish glass demonstrates the potential of an archaeometric approach to shed light not only on the production and trade of glass on the Iberian Peninsula but also on the ancient and medieval economy more generally. ; El estudio del vidrio antiguo y medieval ha permitido identificar distintos grupos composicionales que son resultado de las características químicas de las materias primas empleadas en su fabricación. Los análisis arqueométricos permiten determinar la procedencia del vidrio, demostrando que el vidrio primario fue producido y comercializado a gran escala a través del Mediterráneo durante la Antigüedad y la Edad Media. Los talleres hispanos importaron vidrio primario desde Próximo Oriente durante la mayor parte del primer milenio d. C. siguiendo un patrón paralelo al resto del Mediterráneo. Sin embargo, algunos indicios señalan que pudieron convivir con vidrios de fabricación local que merecen ser investigados. En el siglo IX el vidrio de natrón fue sustituido en al-Ándalus por vidrios ...

Naples assumed an important political and economic role within the region of Campania during the late antique period. LA-ICP-MS data of 285 glass tesserae from the catacomb of San Gennaro in Naples confirm that the surge in building activities in the late fourth and early fifth century CE was accompanied by imports of new materials for the production of mosaic tesserae. Our results from Naples identify a substantial number of Jalame-like Levantine glasses for which there is no parallel within the Italian Peninsula. Only few scattered examples of this type of base glass are found among the published data from Aquileia, Ravenna and the Villa of Faragola, pointing to a link between the supply of glass and the sites' connectivity and economic strength. This seems to have changed after the fifth century. Elemental analyses, combined with SEM-EDS and micro-Raman indicate that the mosaics dating from the fourth to the eighth/ninth century CE in the catacombs of San Gennaro were overwhelmingly made from reused first- to fourth-century Roman base glasses opacified with calcium antimonate. The reuse and recycling of Roman glass and Roman tesserae is a common feature of mosaic assemblages in Italy more generally. The definition of a Roman spectrum tesserae reference group revealed this dependence on old Roman material throughout the first millennium CE.

Analytical data of Roman and early Islamic glass established several primary glass production groups linked to glassmaking centres in the Levant and in Egypt. In contrast, the activities of secondary glass workshops are largely invisible in the compositional fingerprint of first millennium glass. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of 261 glass finds from the Visigothic settlement of Tolmo de Minateda (Spain) revealed a site-specific contamination pattern due to secondary glass processing and recycling, namely the enrichment of the glass batch by a unique combination of rare alkali elements (Li, K, Rb, Cs). With a median of 21 ppm, Li is particularly distinctive. Elevated lithium contents (Li>30 ppm) are also one of the characteristic features of Iberian plant ash glass from the Islamic period. The earliest known examples of this type of glass were found among the ninth-century remains from Tolmo. ; This project received funding from the European Research Council under the European Union's Horizon 2020 Research and Innovative Programme (ERC-CoG-2014, grant number 647315 to NS), as well as from the "El contexto como herramienta: escalas de aplicación en los procesos de cambio en la Alta Edad Media (CONTEXT)" PID2019-108192GB-I00 funded by the Ministry of Science and Innovation; "Cerámica y Alimentos. Paleoeconomía de la Alta Edad Media en el sureste peninsular" APOSD/2020/2016 funded by the Regional Government of Valencia and the European Union through the European Development Fund R.

Portus Ilicitanus (Picola, Alicante) was the main sea harbour of the Roman Colonia Iulia Ilici Augusta and as such played a crucial role in the supply of fundamental commodities to the Iberian Peninsula. Excavations yielded large quantities of glass in fourth‐ and early fifth‐century contexts. Elemental analysis of 60 samples by laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) confirmed that the glasses were imported from the Eastern Mediterranean. A majority of the glasses correspond to the HIMTa primary production group, which originates from Egypt. The statistical evaluation of published data of 589 HIMT glasses further revealed differential distribution patterns of the HIMTa and HIMTb subtypes between the Eastern and Western Mediterranean, suggesting chronological trends that are linked to wider geopolitical changes. This demonstrates the need for systematic large‐scale approaches to identify supply patterns and possible factors underlying geographical differences and/or chronological developments. ; This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 647315 to NS).

Glass mosaic decorations were used throughout the medieval Mediterranean as a powerful medium to convey religious and political agendas, yet we know next to nothing about the source of the materials and the transmission of the necessary technical know-how. Mosaics are generally considered a Byzantine art form, not least due to their prominence in Byzantine church architecture and because medieval Islamic textual sources assert that the glass tesserae of some of the most important early mosques were of Byzantine origin. This article provides solid analytical evidence that glass used in the tenth-century mosaics of the Great Umayyad Mosque of C´ordoba (Spain) came from Byzantium. Most of the tesserae have high boron contents, for which the only compositional match are Byzantine glasses made with raw materials from Asia Minor. In addition, some of the glass has a chemical fingerprint that suggests that it was prepared by mixing local raw materials with imported high boron glass, indicative of local mosaic glassmaking. Our study thus illustrates the value of analytical studies in re-assessing long-held assumptions about the making of mosaics as well as the movement of materials and people across cultural barriers. The presence of Byzantine materials and craftsmen in C´ordoba demonstrates that Muslims and Christians were interacting the length of the Mediterranean, corroborating the close diplomatic ties between the Caliphate of C´ordoba and the Byzantine Empire during the tenth century. Our findings further underscore the importance of glass in trade and diplomatic exchange, reflecting its cultural and economic value in the medieval world.