"Steve Firth" wrote in message
. ..

IIRC they showed a change over the period of their degree, which is IIRC
four years, either that or it was a change since the building was
compelted, I forget it was close to 30 years ago. The glass they were
looking at was the covering of their own building which used very large
vertical slabs of glass.

It was the first time that I had heard that glass flows so I remembered
it for that reason alone.

It's news to the field of glass technology. The original story is about
cathedral glass that has flowed to be thicker at the bottom over several
centuries. In actual fact it was probably installed with the thickest edge
at the bottom.

I've seen apparently cool glass that has flown out of cracks in a lead glass
furnace, but not actually flowing. The viscosity at room temperature is so
high that it has a relaxation time of a few million years, so it must have
been heated for a brief period of time, and then cooled again. It is
physically impossible for cold glass to flow.
--
Terry Harper
http://www.terry.harper.btinternet.co.uk/