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Re: Missing term



My text uses the example of the demarcation of liquid to solid at ~ 1E15
Poise.

A one inch cube supporting a man will deform ~ 0.1'' in a year. As soda
lime glass at 0 deg. C has a viscosity of ~ 1E20 I doubt that any window
would visibly self deform from the time glass was first made in ancient
Egyptian times to the present. [I wonder how "they" arrived" at 1E20.]


I grew up ina house with rippled windows and thought (HS - College?)
they had flowed. Until 1952 (Sir Alastair Pilkington), glass was
rolled and mine (ca 1910) rather poorly.



let's see: 1E5, a tenth million years. Maybe in Iraq it might be
1E4! Did a Mesopotamian scientist set up a glass sheet for us to find?


bc not an urban myth, but a science myth?

Brian Whatcott wrote:

At 10:03 AM 8/29/2003 -0700, BC, you wrote:


////
Regarding freezing, I think one should differentiate between the
increase in viscosity when glasses are cooled and other liquids
crystallize. Glasses are still liquids when called solids because they
still flow and there is not a demarcation in their properties.



///



bc




There seems to be quite a wide acceptance of the idea that
solidified glass flows. This position is supported
by the assertion that medieval church glass is thicker at the foot.

The creep, if I can call it that, apparently takes place over very
much longer time-scales, so the concept is not so clear cut.


Brian Whatcott Altus OK Eureka!