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Old 03-30-2005, 01:06 PM
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Pete VanderLaan Pete VanderLaan is offline
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Location: Chocorua New Hampshire
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Quote:
Originally posted by Lani McGregor
Pete, I’d still argue that you weren’t adjusting to a 96 COE, you were adjusting to fit SP87.

Do all glasses with a 96 COE fit SP87?

And you think viscosity is confusing?

BTW what’s the AP of SP87?



I don’t understand how the compatibility problem is even “seemingly” defeated if it’s only compatible until you cut into it.
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That's why I said that the viscosity issue has never gained any traction. Glassblowers seem to be content with the notion that they can't cut and grind their work made with a lot of german color rods. It's bizarre but people seem very accepting of it. I don't disagree with you. It would seem as long as it doesn't actually explode, it's OK. How many people have you seen who still try to use bright canary yellow opal from Kugler. It doesn't fit anything on the planet. It still sells and if you don't grind it, it holds together for some time if you use cullets that are nearer to a 90.

I have been a vocal minority for a loooong time that the glass made in the 70's and 80's well may be the cullet of this century in due time. It's like pushing back the tide. I am simply stating the way I perceive things to be.

As to all glasses that have 96 C.O.E. fitting Sp87, no I don't think that but I think it based on the thickness of the two glasses that are present. I make opals at 96 that saw and grind with SP87 just fine if they are under one inch thick. Go over that and they don't fit. Why? my hunch is annealing range, not point.

You live in a casting world where thickness is a day to day issue. Things crack. They don't crack in blownware and the schools have absolutely no technical interest in this crap at all anymore. They have all adopted Dale's out of sight out of mind approach to broken glass.

As to the argument about what we were aiming at, I measure my glasses as a 96 on a dilatometer. I do that because I can usually measure SP87 as a 96 or very close. I make the number my target these days. I don't actually have any SP87 in the building right now and haven't for about a year. If SP varies, and it does occasionally, I simply can't try to follow the day to day vaguries of the soap opera. I need to be within 1.5 ten thousandths., that's all.

The annealing RANGE of SP87 is about 890 to 945 depending on thickness and how fast you want to anneal it. I put away large grinding blanks that are thick at 995 for about an hour before dropping to 940. If I don't, I have really cracking issues on grinding them or I have to anneal them at 940 for way to long a time.

When Croucher and I made our presentations at Corning back in 2001, Frank Wooley, senior melt engineer at Corning was there and got into the Q &A very actively. I made the assertion that a substantial number of "Checks" in pieces were really being mistaken for incompatibility when they were actually annealing problems. Frank became very animated in agreement. We talked about it for some time.
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