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Old 05-07-2018, 01:40 PM
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Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 21,924
Pete VanderLaan is on a distinguished road
Linear expansion Coefficient L.E.C describes the linear expansion of a glass, nominally in a 4.000 length approx 4mm in diameter heated from 19C to 300C.
That's where your number comes from.

Coefficient of expansion doesn't even say what kind of expansion. C.O.E. I believe was an expression Theresa at C&R Loo used way the hell back when, and she was trying to get some useful information out there about what might fit what when information was in short supply. It does not mean anything however, thus my objection. Lani MacGregor queried about this and you can find the thread on that in Antiques and Classics.

Since varying thermal guides have been used in various tests, the temperature range has varied. Some systems tested from 19C to 300C, some tested from 200C to 400C. There's a lot of odd stuff but it becomes apples and oranges. So you get to where SP87 is actually a 96... E &T never tested colorants at all. Winkleman and Schott did do an enamel study back around 1925 for that industry on many metallic oxides but the temp ranges were not comparable. A major mistake was made in 1975 or so when Paul Manners put together an article for Glass Magazine called "Custom Made to Fit" which was a very helpful application of Algebra to the issue. There was however a fatal flaw and Paul co-mingled the different studies into one chart. Then Henry Halem canonized that mistake by including it in Glassnotes 3. Fortunately Henry removed that at my urging before Glassnotes 4 was taken to print. Appen does have a far more complete set of factors but it does assume you will calculate your glass using mole chemistry to really be accurate.

Where are we going and why am I in this basket?
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