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Old 08-10-2019, 09:22 PM
Paul Stout Paul Stout is offline
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Question Blue Sulphur

Weyl, in Coloured Glasses (pg. 257-258), and Volf, in A Chemical Approach to Glass (pg. 538), describe making a pure "ultramarine sulfur blue". They both point out that this is done in "borate melts". So my questions are a)has anyone here ever tried this? And b) Is a "borate melt" a batch that contains borax/boric acid or is this implying that it's only attainable in borosilicates? Im going to be doing some sulphur melts/experiments in the next month and thought I'd give the sulphur blue a try, if anyone has any experience to share, I'm all ears. Thanks!
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Old 08-11-2019, 07:18 AM
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Pete VanderLaan Pete VanderLaan is offline
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I have never done a melt in sulfur that did not do one of two things.
A: make an Amber
B: Really stink up the joint.

I'll read about it. If it does do what you suggest, it would likely be in a boron based glass but I have never heard of it.
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Old 08-11-2019, 10:58 AM
Paul Stout Paul Stout is offline
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ďThe process for making these glasses is quite simple. Sulphur, or an alkali sulphide, is dissolved in molten borax, and into the brown melt excessive boric oxide or phosphoric oxide is stirred. The color changes at first to dirty yellow, then to Grey and finally into a pure blue. This blue color being due to elementary sulphur cannot be obtained in glasses which contain major amounts of zinc, cadmium, or other ions of heavy metals with a pronounced affinity for sulphur.Ē
-Coloured Glasses, Weyl, pg. 258
Sounds like a fun, if stinky, experiment if nothing else!
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Old 08-11-2019, 02:37 PM
Bradley Howes Bradley Howes is offline
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A borate glass, as I understand it, is a single component glass that is made up of B2O3. It melts into a vitreous soup at 450ļC (842ļF). Strangely, it has a coordination of 3, that means for every boron atom, it is bonded to 3 oxygens.
I've used boric acid as a flux to purify some gold. The gold formed a bead at the bottom of the crucible and the glass above it dissolved most everything that wasn't gold. When this glass is poured out of the crucible, it starts off perfectly clear and transparent but within an hour, the surface becomes cloudy because it absorbed water from the air. For any glassblower that primarily uses silica as their glass former, borate glasses aren't compatible in any way.
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Old 08-12-2019, 12:54 PM
Josh Bernbaum Josh Bernbaum is offline
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Copper and cobalt donít smell.
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Old 08-13-2019, 10:10 AM
Paul Stout Paul Stout is offline
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Thatís true, and I do love copper blues, but Iím going to be using sulfur in the traditional way anyhow, so why not try (in the quest for knowledge and understanding and such). Also supposedly the blue comes from elemental sulfur which doesnít stink, only itís compounds do, so theoretically this sulfur blue wouldnít smell either. But not having done it yet, I donít know. Iíll post results, good, bad or indifferent just in case anyone else is interested.
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