I know that one way they used to make window glass was to blow a big glass
bubble and then roll it flat. Pressure prevented flattening of the last
little bubble. I have seen examples of this kind of glass at Saint
Augustine FL.
Regards.
Max. K 4 O D S.
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----- Original Message -----
From: "J. Forster" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Monday, June 15, 2009 4:34 PM
Subject: Re: [time-nuts] Lifetime of glass containers
Interestingly, I recently had dinner with an archeology professor,
interested in the Etruscan period. She had just discovered a flatish piece
of glass i9n a dig, thousands of years old, and believes it was made
essentially like rolling out dough on a slab while red hot.
-John
=============
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Dave Carlson
Sent: Monday, June 15, 2009 12:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lifetime of glass containers
Not to charge in, but I've looked at ordinary window pane
glass in very old buildings and you can actually see the
rippling effect that occurred over time, showing the "flow"
of the glass toward the lower edge of the pane. One presumes
that the panes were relatively uniform when installed 120
years earlier. Sounds liquid to me.
Nope.. 120 years ago, I don't think they had modern float glass or even
continuous casting processes.
You blew a large cylinder, cut it open, and laid it flat in an oven, or
took molten glass, poured it onto a flat surface, rolled it flat, then
polished it (with a "plate" hence the name "plate glass")
Sometime early in the 1900's they started making glass in a sort of
continuous casting process with slots or rollers or some such scheme to
make sheets, but it wasn't very flat in an optical sense.
After WW II, they developed the float glass process, where the molten
glass is floated across liquid metal, giving you continuous production
AND
flat surfaces.
So, what you're seeing in old buildings is the fact that flat glass was
really hard to make and expensive. You might use it in a mirror, for
instance, if you didn't use polished metal instead.
I'm sure wikipedia has more than anyone would want to know about sheet
glass manufacture..
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