Re: [ATM] glass blank

[Mark Holm <mdholm@telerama.com>]

Actually it is a sodium calcium silicate.  That is why they call it soda 
lime glass.  Sodium from the soda.  Calcium from the lime.  Silia from 
really clean sand.

Pyrex substitutes a smaller amount of boron for the calcium.  The 
melting and annealing temps of Pyrex are significantly hotter than soda 
lime glass, and it is considerably more viscous.

You can certainly melt soda lime glass in a well designed charcoal 
fired, furnace.  Maybe well dried wood would work.  Probably a 
reverberatory design or a recuperative design to maximize heat use as 
Ellen suggested.  Almost certainly forced draft.  Now, whether you can 
control the heat well enough and long enough to get a usefull product. 
That is a major challenge.  I think I'd use the wood to heat my house, 
and hook up the natural gas line to the glass furnace.  Cleaner and a 
lot easier to control.  Plus, I could let a pyrometer and controller 
tend the fire so I wouldn't have to tend and stoke the thing 24/7 
through the annealing schedule.
-- 
Mark Holm
mdholm@telerama.com
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