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Old 02-01-2019, 10:05 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,258
Pete VanderLaan is on a distinguished road
Cut it out.

It strikes me that one needs to consider the classic formations that help define what is and what isn't a glass. If I look to a material that seems to have no softening point and seems to have an irregular molecular structure that doesn't crystalize forming regular molecular structures then I want to see what makes it stop being a glass. Do you think adding 5lbs of cobalt oxide to 20 lbs of a good formula will still be glassy? 5lbs of clay? 5lbs of alumina?

If I added 15% alumina to many glasses, I don't expect it to be a glass anymore. If I added 20% china clay, I wouldn't expect it. Those are clearly higher limits but the eutectic as shown by Scholes gives direction to various materials that can be and are added to the material and the general direction the material is heading. So, do please read Scholes, Modern Glass practices and look at the illustrated page showing the tendencies.

I understand the error, sort of. The difference between .2 and 2% is large and not noticing the error is worrisome in itself, particularly if one is asking a question about devit, the formation of regular crystals in an irregular molecular structure.
If I went back to the early period in modern studio glass, I tend to think that Bullseye was right about looking for a 90 L.E.C. instead of the 96 that we have but 96 is never going to go away. So, we have this stuff which is a bit less stable than their glass and when you dink with it in ways that industry never contemplated, heating and cooling forever, chances are you'll have problems. Again, crystals grow, they collapse, they grow again until spent and your visual experience with that glass is altered. The color's gone. The opacity is muted or gone. Glass is not static. It gives you some elbow room but it does not have infinite patience with you.

I would think that bathing the chrome in lithium , assuming it is introduced as a sodium or potassium dichromate would really help flux it but even so, there are limits. When Gaffer makes a rod, they don't endlessly heat and cool it. They make rod based on sound chemical expectations that the studio inevitably screws with.

Recently, I've gone around with the issue that this is somehow being kept secret as a sort of plot. It's not. I don't have a fix it answer about the chrome. I don't have a fix it answer for making people quit using boron as a universal flux . I just know the kinds of troubles to expect from it when present in glasses containing other molecular compounds. Not unlike Calcium and phosphorous. We know what will very likely occur combining those two materials. Avoid it.

It's confusing though.
Where are we going and why am I in this basket?
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