[time-nuts] Lifetime of glass containers

[Max Robinson]

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.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
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: time-nuts-bounces at febo.com
>>> [mailto:time-nuts-bounces at febo.com] 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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>
>
>
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