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Tips, Techniques, and Questions -- Technical questions or tips

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  #1  
Old 2024-05-06, 11:19am
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jesnbec73 jesnbec73 is offline
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Default Selenium Glass Looses UV Reactivity?

Got a bit of a conundrum, thought maybe somebody here might know something about it...

I recently ordered some glass shards that a guy excavates from an old glass factory site on the shores of one of the great lakes. It is a yellow glass, originally made for some type of lenses, and is very UV reactive, and glows a really bright orange. I got excited about making some UV reactive minis out of it, ordered a decent amount of it and when I heat it up, it strikes to a red-orange and completely looses it's UV reactivity.

I'm pretty sure it is a selenium based glass, but that is an educated guess at best. Does anyone know why it is losing it's UV reactivity when heated, and maybe if there is some method of working this glass to retain it? Never seen a prettier red-orange colored transparent but once it shifts from yellow to orange, the UV reactivity is gone.
Argh!!!

*There are also some shards or a red glass that glows pink in UV light, haven't heated it yet to see if it is going to be the same, and there is some purple-ish glass from the same location that the guy says is UV active also but it must be responding to a different wavelength because it doesn't fluoresce in my blacklight at all.
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Old 2024-05-06, 2:26pm
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OK, so here's what I know and I'll wait for others to add to the knowledge base. Selenium melting point is lower than most glass torch/crucible temps. The longer it's worked the more selenium it loses. So work fast and low temp as possible to retain any UV reactivity. That doesn't allow for much finesse, but so be it.
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Old 2024-05-07, 5:41am
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The red/orange UV active colors are notorious for burning out in the torch flame unless handled extremely carefully. Just as ESC says, the selenium burns out or reacts to for a different glass. A few boro folks have made it work by sleeving the UV reds and Oranges in clear before working it, then making sure to keep the working heat extremely low, but even enough heat to build up a gather can burn out the UV reaction
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Old 2024-05-07, 1:21pm
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Dangit! I'd try encasing it but I've not got a clue as to the COE. It does seem to be a softer glass though. I'll have to see if I can figure out what temp it starts losing the activity at, maybe I can still do something with it in the kiln. If I can get it to fire polish, and slump or fuse before it looses the UV properties, maybe it won't be a total loss. That red-orange it strikes to is pretty stuff as well so if worse comes to worse I guess I could make a bunch of spacers or something with it LOL

Sounds kind of interesting though, make you wonder how in the world they batch this stuff, must have been a dangerous process. All I know for sure about it is that it was used to make some kind of industrial lenses, you can still see the little indentations on the surface. Don't know who the manufacturer was, but it must have spent a pretty good bit of time on the lake shore, there is some erosion on the surface.
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