A Fragile Heritage
Cambridge - Wednesday 6th September 2017
Aspects of Historic Glass
article posted 12 Aug 2017
Laura Ware Adlington is a PhD researcher in archaeological materials science, based at the UCL Institute of Archaeology. Her work is focused on the study of medieval stained glass in England through a materials science approach; in particular she has focused on the development of a methodology using handheld pXRF to study aspects of the life histories of medieval windows.
Origins of stained glass in the Great East Window of York Minster
Ian C. Freestone1, Laura Ware Adlington1,
Jerzy J. Kunicki-Goldfinger2,
Matthew Thirlwall4, Heather Gilderdale-Scott4, Tim Ayers5
Created by the master glazier John Thornton of Coventry between 1405 and 1408, the Great East Window (GEW) is the largest expanse of stained glass in the UK, comprising 311 individual panels, each containing hundreds of fragments of glass. It tells the history of the World from beginning to end, based upon the Books of Genesis and Revelation. The window is currently the subject of a major conservation project, which has involved its dismounting and the removal of the glass from the lead cames. During the conservation process, the opportunity has been taken to sample glass from selected panels while they are in the conservation studio and subject them to physico-chemical analysis to determine their technologies, provenances and durabilities.
This paper focuses upon the provenance of the glass used in the window. The analysis progressed in a hierarchical fashion, so that large numbers of samples were analysed for major elements using SEM-EDXA or EPMA, a sub-sample for trace elements by LA-ICP-MS and a relatively small number for neodymium and strontium isotopes by thermal ionization mass spectrometry (TIMS).
A number of base glass compositions are recognized in the GEW. Two major glass types are original.
Both contain around 11% K2
O, but the blue, red and murrey colours have higher CaO (c. 22%) and lower MgO (c. 4%) than the whites (15% CaO, 7% MgO). The white glasses show a higher enrichment in light rare earth elements (LREE; La/Yb) and lower Zr/Cr. Analysis of glass from late medieval workshops in England reveals that the products of a number of these in both Staffordshire and the Weald show similar LREE enrichment and low zirconia. Elemental and isotopic data combine to indicate a specific workshop in the Midlands as the probable source of the white glass. The coloured glasses do not match the English sources and are likely to have been imported. Comparison of these results with a number of other windows attributed to John Thornton, from York Minster, Coventry Cathedral and Hampton Court (Hertfordshire) indicate that Thornton used the same sources of glass over a considerable period. As far as we are aware, this is the first time that it has been possible to assign the manufacture of glass used in a major medieval window to a specific workshop.
1 Institute of Archaeology, UCL, 31-34 Gordon Square, London WC1H 0PY
2 Institute of Nuclear Chemistry and Technology, Dorodna 16, Warszawa 03-195, Poland
3 School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, Wales, UK
4 Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
5 Department of History of Art, University of York, Heslington, York YO10 5DD, UK