The windows of Elgin Cathedral have been empty of glass since the 1600s, leaving the colour and pattern of the stained glass up to the imagination of visitors.
Now, scientific testing of the cathedral's window glass has revealed more about its colour, origin and Scotland's trade routes in medieval times.
Thirty shards of medieval window glass from Elgin Cathedral were tested by scientists at Heriot-Watt's Edinburgh campus. The shards were tested using the university's state-of-the-art electron microscopy facility and x-ray fluorescence to identify the elements present, which give glass its colour.
If we can find what the windows looked like, it can tell us about what religious orders and fashions came in to Scotland, what saints were idolised, who funded the construction of churches, and where the builders, glass and glass decorators came from.
Funding from the Society of Antiquaries of Scotland and Historic Environment Scotland led to the first laser-ablation spectroscopy analysis of medieval Scottish glass, and revealed the trace and rare earth elements present in a concentration of less than one part per million in the fragments.
Helen Spencer, a PhD student in Heriot-Watt's School of Energy, Geoscience, Infrastructure and Society, said: “Worship was a major part of medieval life, and the importance of decorations on church windows cannot be overstated. Depending on the time of day, different windows would illuminate the worshippers. Evensong would have a different colour and character to morning worship.
“If we can find what the windows looked like, it can tell us about what religious orders and fashions came in to Scotland, what saints were idolised, who funded the construction of churches, and where the builders, glass and glass decorators came from.
“Unlike most countries in Europe, there is no surviving medieval window glass in situ in monastic or ecclesiastical buildings in Scotland.
“This means we rely on recovered fragments to learn more about glass from this period.
“The tests we carried out have shed light on the colour and origin of the window glass of Elgin Cathedral. We now know, for example, that in the thirteenth century much of the glass came from northern France, while a smaller group may have been manufactured in Germany.
“We identified two distinct blue glasses, both containing cobalt. While one was very dark and rich in potassium, the other a light blue that is richer in calcium, sodium, phosphorus and aluminium. The lighter glass was coloured with bronze, while the darker blue most likely had brass filings added. Both these blue glasses were sourced from different parts of Europe.
“We also found that the brown and amber glasses had quite different base glass 'recipes' to the greens and pinks, meaning they were likely made at separate locations before being imported to Scotland.
“Scotland didn't manufacture glass in the medieval period, although several regions in England produced white 'colourless' glass. At the beginning of the 13th century, much of the white glass came from Normandy and by the 15th century it was coming primarily from Flanders.
“Monastic connections and new trade routes from present day Belgium that connected to east coast ports like Leith, Perth and Aberdeen all had an impact on the glass that was commissioned and used for these beautiful cathedrals.
“Understanding more about these sites brings them to life. The more we discover about our historic buildings the more we can appreciate our history, how people lived, the connections between Scotland and Europe at that time and the craftsmanship involved.
“The next time you visit a ruin in Scotland, take a look at the window spaces and imagine them filled with blue, pink, yellow, green and amber glass from across Europe. It will change how you think about and experience these buildings.”
Dr Simon Gilmour, director of the Society of Antiquaries of Scotland, which funded the laser ablation testing carried out by Helen and the wider Heriot-Watt team, said: “The Society of Antiquaries of Scotland was proud to fund this project.
“The lack of research about window glass used in Scotland during the medieval period was highlighted in the Scottish Archaeological Research Framework and this project has been able to use cutting edge technology to enhance our knowledge of how these ancient windows were made.”
The Heriot-Watt team is testing medieval window glass from across Scotland, in the first comprehensive study undertaken since the 1980s. The team hopes new, advanced testing techniques will uncover more secrets from Scotland's cathedrals.
The research was funded by a generous grant from the Society of Antiquaries of Scotland, and was co-funded by Historic Environment Scotland.