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You're going to want to label this - otherwise - you're going to get it mixed in with your black.
Not that, if you are making solid, self-coloured beads, you'd actually be able to tell the difference!
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This is a very dark transparent grey, slightly streaky. You can see from this test paddle, I had to squish part of it with tweezers to get it thin enough to show that it is a transparent. (The thin part is 2.4 mm, the thicker part, by the rod, is 4 mm.)
It looks somewhat brownish when hot.
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Here - a spacer made with the Charcoal - it looks black!
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The two flanking spacers are both solid Charcoal - the one on the left was reduced, with no apparent effect.
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The Charcoal on white shows it's true nature - when melted very thin, it show a very nice, pure grey, with no overtones of blue, purple, or anything else.
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Closer examination shows that there has been some separation in the white, and that the Charcoal bleeds into the white.
Not what I'd call a hugely useful colour - as I am not a fan of grey (the whole point of glass is the colour!) - but it's very nice to know it's there if you want it!