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Old 03-30-2005, 10:45 AM
Lani McGregor
Posts: n/a
Originally posted by Pete VanderLaan
I really think that L.E.C. works so well for glass blowers that the viscosity issues have just about never concerned them.
Pete, IMO what works well for glass blowers is glass blowing. Not LEC. I happen to know three glassblowers who started a glass factory and found out – while trying to fit different colored glasses together in streaky sheets – that after sending in numerous tests to laboratories (late ‘70s) they could only make the glasses match by INCREASING the difference in their COEs (0-300C). Everything they thought they knew about expansion and fitting colored glass had only taken them in the wrong direction.

Where I think the problem lies, is in the gross generalization that such things as "96" guarantee you a clear blue sky and great sailing.
Exactly. COE is half of it. Viscosity is the other half. One without the other is certainly a place to start, but is misleading. Matching COEs only works if the base compositions are the same or very similar. Who can make a broad color palette with only one base composition? Bullseye has at least five different base compositions for its line of colored glass. If we made the expansions the same on each of these they’d be grossly incompatible.

At the time BE developed its Tested Compatible line Boyce (ever the salesman) liked to call it “90 COE” and, IMO, intended to take over the kiln world at that “expansion”. Dan was never completely comfortable with the corruption of glass science entailed in that kind of marketing. Of course they could have called the glass “990 AP” instead of “90 COE” and been equally right – and equally wrong. For accuracy, it would have been more accurate to call it a 90/990 glass.

I’m just curious as to where the COE as a synonym for compatibility first entered the marketplace and hot shop. When did color bars or batch start to be listed/distributed in those terms?

And I’m talking measured (i.e. at 0-300C) not theoretical or calculated COE. Lots of people were doing calculations. But to our knowledge the practical testing done in factories on a daily basis has always measured the “fit” between glasses, i.e, the combination of expansion and viscosity – NOT the COE.

When did SPB first list a measured COE? I’m pretty sure that what Tom and Henry are talking about in terms of Labino’s formula is calculation.
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