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Old 05-30-2012, 07:15 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
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The Steel work is done, courtesy of great work from Lawrence Duckworth. Charlie is finalizing the AZS liner stuff, which is the slow part. I think we'll see glass by Christmas. I would be surprised if it can be faster than that. It's quite the beast.

My belief about the borax which, keep in mind is a mix of sodium and boron, is that is that it becomes a dissolving catalyst when combined with barium in any glass. I cannot prove that but I've seen glasses that contain both before and they have all had this problem. I believe the nuggets are very close in formulation to the early Crystallica glasses that came out of Europe. Barium really loosens a glass up but most people use it for brightness. Couple that up with the effect that Borax has of both softening while maintaining Linear expansion pretty much and you have a material that is very fluid and can really get into the spaces between the tabular alumina grains in the pot. Frank Wooley used to say to me that no one glass is more corrosive than any other and that it was just a question of viscosity at any fixed temperature but this stuff seems to prove that generalization incorrect since the stuff seems to attack everything made of silica, alumina or fireclays. It reminds me of my fluorine melts is its aggression. SP87 does not contain borax but it does have barium and it is simply not reactive with furnace parts in such an aggressive way.

What seems to me (and I'm making an educated guess again,) makes the spectrum nuggets so corrosive is that they haven't actually completed the chemical reaction from being melted. They are still gassing off. So, when they get put in an electric furnace with no vents the furnaces , it's a recipe for dissolution. At the very least the furnaces need to be vented and none of the electrics were designed that way. Comparatively, electric furnaces are a fairly recent step in evolution and it just wasn't anticipated as a problem.

I recently rebuilt the door on mine and installed a vent and it's remarkable how much crap comes out of that hole in the form of yellow crystalline stuff. I plug the hole when I'm not charging. My glass formulation does have Borax in it although very little, 1.65 lbs in a 78 lb mix but it contains no barium. I don't have trouble with it beyond the pot slowly dissolving which is a cost of doing business.
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