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Old 03-31-2005, 09:34 AM
Lani McGregor
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Re: AP

Quote:
Originally posted by Tom Littleton
Lani,
From Frank Woolley (data from a Melt at the Studio at Corning in 1997). Softening point 666 degrees centigrade(1231degrees F), Annealing point-492 degrees centigrade (918 degrees F), strain point-455 (851 degrees F), expansion (0-300 degrees) 94.9.

CAVEAT- None of these figures should be taken as gospel, a holy grail, something that everyone is going to get every time they melt. Variations in raw materials, frunaces, melting techniques and other factors will cause differences in the glass. Not to mention Frank told me that the dilatometer measurements were plus or minus one point in accuracy.

Have I put enough qualifiers in here yet?
Perfect! Thanks heaps, Tom! So what you've got - IF all the qualifiers are taken into consideration - is a glass with a 94.9 COE and an AP of 918F.

I'd wager that any colored glasses that fit that base clear (i.e. show little stress in a ring, pull, Trident seal or BE chip/bar test) but have a much lower AP (such as a lead glass would) will NOT have a 94-95 COE. Their measured LEC (0-300C) will be lower.
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