Last week I got an email notice of a new podcast that promised to “Expand Your Mind and Explode Outworn Beliefs!” (more…)

It’s a weird business climate today. On the one hand, anything you write from inside a for-profit business is going to be met with skepticism. On the other hand, a lot of people still buy into commercial messages without question.

When will she quit??!?? Soon. Soon. Meanwhile, here’s a laboratory test glass with a measured COE of 89 (sorry, the 90 COE lab glass that we’d tested previously has been discontinued). According to popular understanding this glass should be within the range of expansion mismatch for a COE 90 glass (plus or minus 1 COE point). Not.

I’ve been ranting for weeks now about the misunderstanding of the Coefficient of Expansion within the studio glass community. Steve from Glasgow made the brilliant if obvious point in a comment to my April 11 posting that we’ll never get rid of this use of the COE as a shorthand equation for compatibility until it’s replaced with something else.
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After dragging you tediously through how we test for compatibility, what the COE is, how it is tested and what it does NOT tell us, the obvious question is: So, who ever suggested that matching COEs could identify compatibility in the first place?

We did.

GETTING OUT FROM UNDER SOME SERIOUSLY OLD INFORMATION. Written almost 25 years ago by my partner Dan and his then-partner Boyce, Glass Fusing Book One was the first – and is still the most definitive – book ever written on the subject of kilnforming. Today, even Annie is too smart not to dig out from under that old story.

Yes, this entire mess started at Bullseye. We made a mistake. We (actually, it was Dan Schwoerer and Boyce Lundstrom. I wasn’t here at the time, Your Honor) believed that matching the LEC would insure that glasses “fit” when fired together.
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READY, FIRE, AIM. Before you start kilnforming on this scale, you might want to understand what you’re doing.

I was about to unmask the fools who started the COE mess when I got a private email asking me why I was making such a fuss about compatibility standards when – by our own admission – Bullseye’s are likely tighter than they need to be.

First of all, that wasn’t quite the point of my rant, but I’ll take a momentary detour here to explain why this stuff matters…
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I’ve got a brilliant vet. She’s coming to our home to help Ed “pass over”. I wish there were a glass doctor who’d do the same thing for the sick old myth of the COE.

Fat chance. This misunderstanding about compatibility and the Coefficient of Expansion has been around for longer than many people have been fusing. They were raised on it. Sadly, it may be around forever, mucking with basic technical information in our field and making it harder for users to solve problems when they occur.

We’ve never labeled Bullseye glass as “90 COE”. At the beginning, we labeled the sheets – and still refer to them today as – TESTED COMPATIBLE. Due to the confusion that arose when other companies entered the market and adopted the term we’d coined, we now label our sheets BULLSEYE COMPATIBLE. My two earlier blogs in this series define exactly what this term means.
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