[ATM] Re: Annealing

[vorblesnak@peak.org]

Having begun the long ramp to understanding glass so I can slump it and
make a mess of it, I have done a bit of study on Pyrex and how to make it
work.  I still know nothing.  BUT!  I did get some info from two
individuals on this list about Pyrex.  Neither name is on this PC and my
mind is Swiss cheese these days, so if they recognize me or the allusion,
maybe they will reply.

One is in Portland Oregon and is making a furnace to process Pyrex.  He
talked about the need to allow the Pyrex to fully 'bubble', that is allow
the bubbles to percolate out of the mix before casting the blank. 
Annealing was not just a soak at one temp, but a gentle cascade through a
range of temps to allow crystal growth and positioning.  Anneal is the top
end, strain is the bottom end of that temperature range.

The other is down south somewhere and the comment that comes to mind is
time per thickness.  The numbers were, I think, 1 hour per inch of
thickness, including the thickness of the shelf used, per soak point.  So
on a 2 inch blank on a 1/2 inch shelf, you would need to soak, (hold that
temp), for two and one half hours.  And the same at the next point.

Now it seems to me that a good glass kiln with proper controls could pay
for itself very quickly doing annealing.  That is assuming the glass is as
bad as it is reported to be.

David Davis
Toledo, OR  97391

_______________________________________________
ATM mailing list http://www.atmlist.net/