Tuesday, November 25, 2008

An update on medieval glass

My friend Carolyn saw my post about the stained glass windows still “moving” and sent me this link to a NYT article that says that is probably a myth:

It is well known that panes of stained glass in old European churches are thicker at the bottom because glass is a slow-moving liquid that flows downward over centuries.

Well known, but wrong. Medieval stained glass makers were simply unable to make perfectly flat panes, and the windows were just as unevenly thick when new.

Yet most people don’t understand why glass should be a liquid and so, well, solid-seeming. Even physics people are involved in this discussion, with Harvard physics professor David Weitz reported as saying, “It just can get so controversial and so many loud arguments, and I don’t want to get involved with that myself.”

One of the controversies involves why molecules in some part of glass move faster than in other parts—but to the eye, the glass appears the same in both regions.

If anyone can find the article I’m thinking of (circa 2001-02) that talked about conserving Europe’s stained glass, with the lead soldering suffering from the glass seemingly moving, please send a link. Thanks for this one, Carolyn! Lots of food for thought.

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