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Window glass is one of our most important sources of medieval imagery, but our understanding of its production is limited relative to other media such as wall-paintings and sculpture. Furthermore, it represents the majority of the glass material used in the medieval period in northwestern Europe. This project aims to determine
(1) the variability in composition of English medieval window glass and its relationship to date and location
(2) if the glass used by a single medieval glazier over a series of commissions was constant, reflecting a preferred source
(3) the likely sources of English medieval window glass
(4) the relationship between these characteristics and the tendency to corrode
Chemical
compositions of some 860 samples of medieval window glass spanning the
mid-twelfth to early sixteenth century, mainly from sites in England
were determined using SEM-EDXA and trace elements measured in a subset
of 300 using LA-ICP-MS. They fall into two main groups: forest glass,
the predominant type from the 12th-14th centuries, and a new
calcium-rich glass type(HLLA), from c.1400. This unexpectedly early
occurrence of HLLA in stained glass windows strongly suggests that it is
was imported from the continent. Analytical work in support of this
two-source model has not previously been presented.
A particular
focus on the windows of John Thornton of Coventry and his contemporaries
confirmed a consistent relationship between maker, date and material. A
gradual change in composition between 1150 and 1400 probably reflects
the progressive replacement of fern ash by the ash of harder woods.
The
intensive sampling of panels from the east window at York allowed us to
map the use of different batches of glass as work had progressed, with
benefits for conservation in identifying displaced pieces. Evidence
that twelfth-century glass makers coloured their blue panels by adding
old Roman mosaic tesserae to contemporary potash glass is more
convincing than has been previously found, while red glasses appear to
have been made using a completely unanticipated method before 1400 AD,
effectively revealing a lost technology.
Related outputs
- Kunicki-Goldfinger, J.J., Freestone, I.C., Gilderdale-Scott, H., Ayers, T., and McDonald, I. (2014) Problematyka badań witraży średniowiecznych. Archeologia Polski 59 (1-2) 47-78.
- Kunicki-Goldfinger, J. J., Freestone, I. C., McDonald, I., Hobot, J. A., Gilderdale-Scott, H., & Ayers, T. (2014). Technology, Production and Chronology of Red Window Glass in the Medieval Period-Rediscovery of a Lost Technology. Journal of Archaeological Science 41, 89-105.
- Schibille N, Freestone IC (2013) Composition, Production and Procurement of Glass at San Vincenzo al Volturno: An Early Medieval Monastic Complex in Southern Italy. PLoS ONE 8(10): e76479. doi:10.1371/journal.pone.0076479
- Kunicki-Goldfinger J J , Kierzek J, Freestone I C, Małożewska-Bućko B, Nawrolska G (2012) The composition of window glass from the cesspits in the old town in Elbląg, Poland. 18th Congress AIHV Proceedings, 395-400
- Freestone I, Kunicki-Goldfinger J, Gilderdale-Scott H, Ayers T (2010) Multi-disciplinary Investigation of the Windows of John Thornton, focusing on the Great East Window of York Minster. In Shepherd M B, Pilosi L and Strobl S (eds) The Art of Collaboration: Stained Glass Conservation in the Twenty-First Century. New York: Henry Miller for the CVMA.