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?
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.
They even went so far as to write “The range of fusing compatibility is plus or minus 1. Therefore, Bullseye #101F [now #1101F] with a coefficient of 90 would be fusing compatible with other glasses whose coefficients range from 89 to 91. Outside this range, undue stresses will develop in the glass.”
They soon learned that this was only true if the base formulas of the glasses being matched were the same. It was NOT true when mixing different glasses like opals and transparents. They learned, in fact, that sometimes the COE had to be different for the glasses to match.
How did they learn that lesson? The hard way, of course.
They’d been having a horrific run of a blue and purple streaky glass, a combination of an opal and a transparent. It was breaking up as it came out of the annealing lehr. The breaks were obvious incompatibility – along the interfaces of the two colors.
2105 – The glass that taught the Bullseye guys that matching COEs does NOT insure compatibility.
Samples of the blue opal and the purple transparent were sent off to a testing lab to check their expansions. The report showed that the LEC of the opal was slightly lower than that of the transparent. Problem solved: the formulas were adjusted in order to match their expansions.
Result? The breakage got WORSE. The COEs matched perfectly, but the two glasses were now even MORE incompatible.
Now what? When in a corner it’s sometimes a good idea to ram it into reverse. They reformulated the opal to make it even LOWER – to increase the differences in the COEs of the two glasses.
It worked. By making sure that the COEs did NOT match, they could insure that the two glasses fit.
But, before anyone gets the idea that the authors of Glass Fusing Book One were idiots, please read the original text. They knew that the COE wasn’t quite so simple. They cautioned that:
“…some glasses that have the same coefficient number, as determined by a laboratory, do not always fit each other when fused together.”
They went on to point out that how a glass behaved in the upper temperature ranges was also important.
But the damage was done. The EZ-users, the salesmen, the Fusing-for-Dummies set just grabbed the COE and made it into the astrological sign of our industry: “What do you use? 90 or 96?” It got worse:
“If you can fuse it to Bullseye and it doesn’t break, it must be 90!” Who cares if the manufacturer says it’s 94? Let’s just label it 90. It’s easier to sell that way.”
“Hey, this company says their glass is even closer to 90 than Bullseye. They say theirs is 90.0”
“Don’t you know that the standard in glassblowing is 96?” “Think of all the incredible combinations you can do by mixing all those color bars with a 96 glass!” “Wow, what FUN.”
A random sampling of chips from color bars by Reichenbach, Zimmerman and Gaffer fired against a base System 96 clear glass. Is this the same “compatibility” as the standard that Bullseye established for kilnforming so many years ago?
In the rush to make it all look so E-Z, users are being led astray from the basics of our field: the understanding of what compatibility means, especially as it relates to kilnforming. They are also being deprived of the opportunity to learn about a truly fascinating material. Glass, and the properties that make it so interesting to work with, can’t be reduced to marketing bytes without the user losing some of the rich potential that it holds for exploration, discovery and true creativity.
In the commercial carnival that has erupted in our field, essential, valuable, and necessary technical information is being sacrificed for sales dollars.
Does anyone care? You tell me.
Ed didn’t. He got pretty tired of living in a house full of obsessive glass fanatics and decided to bag it.
PS. Lest anyone think Ed ended it in a grocery bag, he didn’t. He was still alive – although a bit zoned in this shot – just enjoying one of his favorite activities on the day before his Big Check Out adventure.