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Old 2007-09-03, 12:45pm
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Quote:
Originally Posted by Dennis Brady View Post
Assuming that COE 104 glass will have a viscosity difference from COE 96 glass sufficient to compensate for the COE difference is an assumption I would never make nor suggest others make. I'll stay with my original suggestion that making that assumption is a risk. Some are willing to take such risks, some are not.
And if you never take the risk, it will continue to be an assumption. I'd like to think that we're all, for the most part, artists. If we're not taking risks, and simply obeying the rules of some amorphous authority out there, we're shortchanging ourselves. And, quite frankly in my opinion, we cease to be artists.

Do I propose going about it all willy-nilly and just throwing glass into a piece and selling it? Of course not. What I am saying is that we shouldn't limit ourselves to some standard that really isn't all that standard. We insult ourselves as artists if we do so.

The concept of COE as it relates to compatibility wasn't even a consideration until some time in the 60's, wasn't widely known about until well into the 70's, and the flameworking world probably didn't glom onto it until the late 70's or perhaps even the 80's. Here is a marvelous anecdotal discussion of the genesis of COE in the states. Anecdotal, but quite valid, the discussion includes many of the players at that time.

As a small aside, one company that is currently at the forefront of compatibility research is Bullseye. A quote from one of the above links...

"Although Bullseye glasses are popularly referred to as being of a "90" expansion, Bullseye does not encourage the use of this designation in describing its glasses.

The "linear expansion coefficient" is determined by a laboratory test, which expresses the average expansion rate from room temperature to 572ºF (300ºC). It ignores the more important range of expansion for determining compatibility for fusing is the expansion through the annealing and softening ranges. It also ignores viscosity, an important element in determining whether glasses will "fit" each other on fusing. All "90" expansion glasses are not compatible."


While this addresses fusing, the points are valid to flameworkers as well. It would appear that Bullseye is looking toward the big picture, their glass is tested compatible. The COE of their glass is apparently 90-ish, but more importantly, the other factors are taken into account so as to create classes that fit.
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