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glass cutting


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From:  gweaver [SMTP:gweaver-at-earthlink-dot-net]
Sent:  Saturday, February 28, 1998 2:13 PM
To:  Tesla List
Subject:  Re: glass cutting



Tempered safety glass is heat treated just like steel.  The glass is heated
in an oven to a certain temperature.  The glass comes out of the oven on a
rolling conveyor system and through a water sprayer system.  It takes
several sheets of glass to get the water sparyer adjusted accurately without
causing the glass to explode.  When the water is adjusted correctly it looks
like a fog blowing on the hot glass that turns into steam.  The glass is
impact tested and stacked into wooden boxes with about 200 sheets of glass
per box with a sheet of white paper between each sheet of glass.  Safety
glass has an impact rating of about 100 lbs. per square inch or higher only
on the flat surface of the glass.  Impact on the edge of the glass in very
low, only a few pounds. Tempered safety glass is very sensitive to SUDDEN
changes in temperature.  You can take a piece
of safety glass from a 70 degree F air conditioned room outside into the 95
degree F hot summer air and the glass will explode in about 15 to 30
seconds.  Tempered safety glass can not be cut.  I have never heard of
anyone removing the temper from safety glass but if you have an oven that
will heat the glass very slowly to about 1850 degrees F then let it cool
very slowly on its own it should
remove the temper. When tempered safety glass breaks it sounds about like an
explosion and the glass goes 15 to 20 feet in all directions.  I use to have
several 1000 sheets of tempered safety glass 27" x 76" and some other odd
sizes that were all rejects from the place where I worked about 18 years
ago.  I built 20 solar hot water collectors for my house and sold or gave
away all the rest of
the glass.  A friend of mine still has 600 sheets of glass in his barn that
he no longer wants that measures 25" x 27" x .150" thick.

Gary Weaver



At 10:45 PM 2/27/98 -0600, you wrote:
>
>----------
>From:  Eleanor Flood [SMTP:eflood-at-bellsouth-dot-net]
>Sent:  Monday, January 12, 1998 2:01 PM
>To:  tesla-at-pupman-dot-com
>Subject:  glass cutting
>
>If anyone out there is planning on making plate glass caps, please be
>warned, our neighbor gave us a couple of fine sheets of Hercules Safety
>glass.  The sheets were 24" long and 8" wide. Harold thought to saw them
>into 8" square pieces to make a glass cap. I do a bit of lapidary work,
>so we have a diamond edge abrasive saw that is used to cut rocks, glass
>and the like.  Harold marked the glass, donned a rubber apron, a hat and
>safety goggles, and turned on the saw.  He had not cut an eighth of an
>inch into that glass when it literally exploded.  There was not a piece
>of it left as big as a match head.  The glass was scattered all over the
>10' x 24' room.  We have no idea what was so different about this glass
>to cause such an event. He frequently saws regular window glass and
>glass bottles for salt water caps with no problem.  Anyway, if you plan
>to saw glass, just be careful.  We also wonder what might have happened,
>should he have had access to the size he needed, constructed the cap and
>put the high voltage to it.  Big explosion?  Anyone know anything about
>this type glass.
>
>Safe sparking, and safe sawing!
>Elli
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