SEM-EDXA of 132 examples of medieval red window glass reveals the presence of around 1% copper oxide in all cases. SEM and TEM of selected samples confirm the presence of Cu nanoparticles. Two structural categories of red glass sheet are identified. Sheets comprising a single layer of red glass from a few tens to around 300 pm thick overlying a supporting substrate of white glass, with or without a protective cover of white glass, are typically found from the fourteenth century onwards. However, in 12th-14th century England, France and Spain, and perhaps elsewhere, typical red glass sheets have a complex microstructure comprising multiple coloured striae about 1 gm thick in a white background. SEM-EDXA, TEM and LA-ICP-MS have been used to characterise and investigate the technologies of the two types in detail. The single-layered glasses were produced using an approach analogous to that of copper red glass in the modern period, where a red glass is flashed onto a colourless base. In contrast, the multi-layered glasses were formed by the incomplete mixing of an oxidised high-Cu and a reduced low-Cu glass. The red colour forms due to the diffusion of oxidised copper into the reduced glass and the nucleation and growth of metallic copper during heat-treatment. This represents a previously unrecognised medieval glass technology, where red was created by mixing two weakly coloured glasses, a complex, arcane and mysterious procedure which must have reinforced the exclusivity of the craft. The occurrence of the technique has implications for dating windows and the identification of glass which has been inserted in early restorations and repairs, for the trade in coloured glass and for the transfer of glassmaking technologies in medieval times. It provides a link between stained glass window technology of the high medieval period and the glass-colouring practices of the late first millennium CE. (C) 2013 Elsevier Ltd. All rights reserved.
Na podstawie badań ponad 900 fragmentów średniowiecznych szkieł witrażowych, pochodzących z różnych miejsc i okresów (od XII do XVI w.), omówionych zostało kilka wybra¬nych zagadnień związanych z metodyką badawczą i interpretacją wyników. Poruszona proble¬matyka dotyczy dziewiętnastowiecznej restauracji witraży i ich współczesnej interpretacji, badań pojedynczej kwatery, okna i zespołu okien oraz szkieł barwnych. W ostatnim przypadku, dokład¬niej zostały omówione szkła czerwone oraz dwunastowieczne szkła niebieskie, wytwarzane przy użyciu rzymskich tesserae
Twenty-seven samples of glass from panel 2e of John Thornton’s Great East Window (1405–1408) at York Minster have been analyzed using energy dispersive x-ray analysis in the scanning electron microscope. This paper highlights our findings. Inserts and replacements of early modern and medieval glass have been identifi ed. White (colorless) and colored medieval glass differ significantly in composition, suggesting diff erent sources. Eleven samples of white glass original to the window are identical within analytical error, suggesting they came from the same batch, but the head of Christ is from another panel. Blue and flashed red glass were each the product of more than one batch of melting. Primarily, the condition of the glass is dependent upon silica content. Further investigations of other panels from the Great East Window, and of other windows by Thornton, are ongoing.
Twenty-seven samples of glass from panel 2e of John Thornton’s Great East Window (1405–1408) at York Minster have been analyzed using energy dispersive x-ray analysis in the scanning electron microscope. This paper highlights our findings. Inserts and replacements of early modern and medieval glass have been identifi ed. White (colorless) and colored medieval glass differ significantly in composition, suggesting diff erent sources. Eleven samples of white glass original to the window are identical within analytical error, suggesting they came from the same batch, but the head of Christ is from another panel. Blue and flashed red glass were each the product of more than one batch of melting. Primarily, the condition of the glass is dependent upon silica content. Further investigations of other panels from the Great East Window, and of other windows by Thornton, are ongoing.
