One hundred and forty-one glass fragments from medieval Ciudad de Vascos (Toledo, Spain) were analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The glasses fall into three types according to the fluxing agents used: mineral natron, soda-rich plant ash, and a combination of soda ash and lead. The natron glasses can be assigned to various established primary production groups of eastern Mediterranean provenance. Different types of plant ash glasses indicate differences in the silica source as well as the plant ash component, reflecting changing supply mechanisms. While the earlier plant ash groups can be related to Islamic glasses from the Near East, both in terms of typology and composition, the chemical signature of the later samples appear to be specific to glass from the Iberian Peninsula. This has important implications for our understanding of the emerging glass industry in Spain and the distribution patterns of glass groups and raw materials. The plant ash that was used for the Vascos glasses is rich in soda with low levels of potash, similar to ash produced in the eastern Mediterranean. It could therefore be possible that Levantine plant ash was imported and used in Islamic period glass workshops in Spain. Unlike central and northern Europe where an independent glass industry based on potassium-rich wood ash developed during the Carolingian period, the prevalence of soda ash and soda ash lead glass on the Iberian Peninsula indicates its commercial and technological interconnection with the Islamic east. Our study thus traces several stages leading to the development of a specifically Spanish primary glassmaking industry.

Significance: The Islamic conquest of the Mediterranean has long been associated with fundamental geopolitical and economic transformations that sundered the medieval world from antiquity. An eighth- to ninth-century glass assemblage from Cordoba provides new insights into the processes of technological innovation, adaptation, and dissemination contingent on the specific historical environment. Its compositional characteristics reveal the mechanisms underlying the development of a new glassmaking tradition that, based on lead isotope analyses, can be attributed to a local production, using raw materials from nearby ore deposits. Our study illustrates that the second half of the eighth century and the ninth century was a period of considerable technological development in al-Andalus, triggered by a rupture in glass supplies from the eastern Mediterranean.

Excavations at the Roman villa of Noheda (Spain) revealed the remains of an exceptionally elaborate fourth-century floor mosaic that contains a surprisingly large number of glass tesserae, representing a broad spectrum of colors. This paper presents the results of the chemical (LA-ICP-MS) and microstructural analyses (SEM-EDS, XRPD) of 420 glass tesserae from these mosaics. The high number of data allowed us to establish the compositional variability and to elucidate questions of supply in relation to a large-scale artistic campaign. The tesserae from Noheda were almost exclusively made from recycled mixed Roman Mn and Sb base glass, thus demonstrating that recycling of Roman base glasses was common practice in the fourth century, occurring on a near industrial scale. It also suggests that the workshops specializing in the production of mosaic tesserae might have been in the western Mediterranean. A limited number of coloring and opacifying additives (Mn, Co, Cu, Sb, Pb) were identified, which resulted in a wide range of hues. These were differentially associated with various trace elements, which implies the use of different raw materials. A sub-set of red, green, and orange tesserae reflect distinct base glass characteristics as well as coloring technologies that point to an Egyptian provenance.

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.

It has long been assumed that lead glazing technology preceded glassmaking in the Western world and that the technological transfer was from glazes to glass. Here, we present new evidence for the reverse, the indigenous innovation of glassmaking and its transfer to glazes in early Islamic al-Andalus (Spain). Compositional analyses show that Islamic lead glazes from Córdoba are intimately related to a distinct type of high-lead glass, suggesting a connection between the two technologies. The archaeological remains from a pottery workshop indicate that the glazing process initially involved the production of a lead glass and is not linked to earlier Roman or other contemporary glazing technologies. The data also demonstrate that the potters not only used the same materials and techniques but borrowed stylistic and decorative models from glassmaking.