[ATM] Re: ATM Digest, Vol 3, Issue 5

[artbianconi at blast.net (artbianconi@blast.net)]

Date: Wed, 03 Mar 2004 10:08:32 +0800
From: Ian McKernan <mckernan@murdoch.edu.au>
Subject: [ATM] RE: Glass Slumping

"I'm thinking that the way to go is heat it to the "slumping temp" of
704C and soak it till its well slumped, then open the door of the 
oven and cool it a couple of hundred degrees."

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Shock cooling is the way we create oil hardened metal tooling. You 
can do that with certain metals.

Too sudden a cooling of glass however, will shrink the outer surface 
and thus create internal stresses that will increase further as it 
cools. The glass closest to the door will cool first so the stress is 
uneven. That's even worse. Then as the glass cools down the stresses 
increase until it creates lots of broken glass.

There is nothing wrong with simply turning off the heat and allowing 
it to cool down slowly. In fact it's preferred.

I'm puzzled why you would invest so much time and effort in such a 
low grade glass.

Art Bianconi