Date:         Mon, 13 May 1996 15:44:00 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Maher, Steve (SD-MS)" <SMAHER@gi.com>
Subject:      Re: Front Glass


> According to information received, the glass should be stamped Sigla 
(which
>is the logo impressed on the broken pieces at the current time), it should
>- - - -
>
>FYI:   glass with the sigla logo is the laminated safety glass, specified 
for
>M america markets.   euro buses have tempered glass windsheilds, on which
>your head will break, if it comes to that.


I had a fireplace with glass doors once, in which I had to replace two 
panels, and I learned about glass that way (the hard way) after trying 
unsuccessfully several times to get it right (my best and only learning 
method). Some of this seemed to relate to auto glass:

On the first try, I put in what they called "tempered glass". Had two
appropriate size panels made, they fit, and there was much rejoicing. Lit
off the fireplace that night, and about twenty minutes later, POW! tiny
pieces of glass, more like little pebbles than slivers, scattered all over
the carpet for a distance of four or five feet from the fireplace.

Cleaned it up, went back to the glass shop the next day, described what
happened. They mentioned that the reason it was used in high-stress 
applications
such as fireplaces, was because when it broke, it turned into those little
not-so-sharp-edged pebbles instead of the long, razor-sharp slivers you get
from broken windows.

They were very apologetic, and cut me two panels of "safety glass". This,
they said, was similar to what you have in auto windshields. It's ordinary
glass, laminated on both sides with thin, clear plastic. If this stuff
breaks, it fills with cracks and slivers, but the plastic laminates keep
the shards from flying all over.

That night, I had the opportunity to find they were telling the truth-- POW.
And yes, the shards did mostly stay in one place, making cleanup easier
this time.

Back to the glass shop, and sought a meeting of minds. No, I did not tap,
bend, or otherwise stress the glass. Yes, I knew what thermal expansion
gradients are, and why a juice glass will break if you pour boiling water
into it. This is a FIREPLACE, and such gradients are inevitable. What's
wrong with this glass you keep selling me???

This time, I paid (relatively) big bucks for their fanciest pyro-ceramic
glass, guaranteed to withstand medium-sized nuclear devices. As I carried
it from the shop, the clerk asked, "By the way... what kind of insulation
are you using to cushion this glass where it sits in the metal frame?"

Quoth I, "Uh... gee... well... what?"

Seems that glass can be set off by ANYTHING hard that touches it when 
heated--
even just the weight of the glass leaning against the metal frame. So I
sheepishly bought some fireplace glass insulation from them (it was even
labelled that way on the package, adding self-insult to self-injury),
lined the glass with it, and never had another problem.

Moral of the story is, there are at least two kinds of safety glass. One
(which I gather is used in cars in Europe) breaks easily and shatters into
little, not-very-dangerous pebbles; and the other (used in cars in the U.S.)
is the plastic-laminate kind, somewhat more resistant to breakage, and which
keeps its pieces to itself when it does break.

The tempered glass, which shatters so spectacularly and showers everyone
with (nonlethal) pieces, is also used in Hollywood movies. They make it
very breakable so that Schwarzenneger won't break half the bones in his
hand when he punches through a car windshield trying to kill Linda Hamilton.
But they used the real stuff in Die Hard and Ghost... very carefully.

After wrapping a 240Z around a telephone pole in New Jersey a while back,
I decided I liked the U.S. kind better. Six months later, the shattered
windshield was still there in the tall grass by the side of the road,
all in one messy-looking unit. But no blood.

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______________________________________________________________________

 Steve Maher         smaher@gi.com           '80 V6anagon w/Chevy 2800
                                             '66 Mustang Coupevertible

            Check out the cars at http://www.wp.com/IrishMafia

              *** There are plenty of jobs around!
                     Hell, I have three of them! ***
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