Westminster Abbey helps shine light on Stained Glass Myth

In the January 2018 issue of the Journal of the American Ceramic Society, John Mauro, a researcher at Penn State University reports on his latest findings, inspired by a visit to Westminster Abbey, during which its surviving stained glass sparked a quest to better understand the science behind the myth that medieval window glass is thicker at the bot-tom because of glass viscosity, or its slow transition to a liquid.

The myth had been questioned and dispelled before, but Mauro and his team were able to establish that this science was off by 16 orders of magnitude: the windows are, in fact, transistorising to a liquid much faster than previously thought. These new findings are the result of a number of methodological improvements by Mauro. First, previous publications considered modern soda lime silicate and germania glass compositions rather than directly considering a real medieval cathedral glass composition. Previous work also did not include explicit fluid-flow calculations and was based on measurements conduct-ed decades ago in the former Soviet Union. Mauro’s own previous research experiences and observations of the behaviour and nature of Gorilla Glass at Corning, over 18 years, also led him to question earlier findings.

Conservationists and historians need not, however, panic too much. The transition is still far too slow for any noticeable difference. It would take billions of years to cause even nano-sized alterations to the shape of the glass. “It was a lot of fun to directly address an urban legend that has captured the imagination of the general public for so many decades,” said Mauro, professor of materials science and engineering. “Glassy materials have captured the attention of humanity for millennia, and I hope that this work will help draw more attention to the cutting edge physics and chemistry that are still hiding in these ancient and beautiful materials.”

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