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Post by opalpyrexia on Jan 9, 2019 14:13:37 GMT -5
I cabbed some mahogany obsidian recently and encountered bubbles that were not at all apparent on the slab that I had purchased. To the eye from a distance they aren't very noticeable, but a photo really makes them stand out: I'm considering mixing up some blackened epoxy and filling the holes, and after curing taking off the excess with a very high grit wheel. How common are these bubbles/cavities? Common to all obsidian?
Is this a reasonable treatment? Should I have asked the slab seller about bubbles prior to purchasing? (Doh!) I would of course disclose the treatment to prospective buyers. Thanks for any guidance.
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Post by Drummond Island Rocks on Jan 9, 2019 14:34:51 GMT -5
I cabbed some mahogany obsidian recently and encountered bubbles that were not at all apparent on the slab that I had purchased. To the eye from a distance they aren't very noticeable, but a photo really makes them stand out: I'm considering mixing up some blackened epoxy and filling the holes, and after curing taking off the excess with a very high grit wheel. How common are these bubbles/cavities? Common to all obsidian?
Is this a reasonable treatment? Should I have asked the slab seller about bubbles prior to purchasing? (Doh!) I would of course disclose the treatment to prospective buyers. Thanks for any guidance.
Can't help with fixing them but I have had those bubbles show up a bunch in my mahogany obsidian tumbles. I have not had them show up in any other variety. Chuck
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Post by Deleted on Jan 9, 2019 14:36:34 GMT -5
Yes, common to all obsidian, particularly at the edges of flows where less pressure allows gases to expand, though not always of a noticeable size. No telling where the larger ones will pop up within a piece, and I doubt the seller could have detected what was further down in the slab if it is opaque. In some obsidian, bubbles are actually features (such as in much of the sheen obsidians where entrained and stretched into micro-thin streams and/or tubes that produce the shimmer), though you certainly don't want large bubbles that will appear as pits. If you are going to tint epoxy, I'd suggest that just a bit of black + brown be used, rather than straight black, since the black in obsidian is almost never pure black. I'd be concerned that a pure black would also stand out on close examination. If you have any dark chips you can grind down to a fine powder and combine with epoxy, you might try that to match the brown-black color (either way, test on a scrap piece before deciding to use on your pretty cab, though).
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Post by miket on Jan 9, 2019 15:55:17 GMT -5
Glad you posted this, I have a load of mahogany going now. It should be done in a week or two, I'll have to watch for bubbles- and not freak out if I see them.
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Post by opalpyrexia on Jan 9, 2019 17:58:21 GMT -5
If you are going to tint epoxy, I'd suggest that just a bit of black + brown be used, rather than straight black, since the black in obsidian is almost never pure black. I'd be concerned that a pure black would also stand out on close examination. If you have any dark chips you can grind down to a fine powder and combine with epoxy, you might try that to match the brown-black color (either way, test on a scrap piece before deciding to use on your pretty cab, though).
That's an excellent suggestion. Thank you!
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Post by rockjunquie on Jan 9, 2019 18:02:54 GMT -5
I think you could use a dark brown fine point sharpie (if there is such a thing) on the pits and fill them crazy glue, but it would depend on what you plan to do with it, I guess. The pits are so small that that should work fine.
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Post by Pat on Jan 9, 2019 18:22:37 GMT -5
I’d be tempted to call them DESIGN ELEMENTS. 😀
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Post by opalpyrexia on Jan 9, 2019 19:11:02 GMT -5
I’d be tempted to call them DESIGN ELEMENTS. 😀
That's funny, but also funny that you would suggest that! Rather than hiding them, I had thought about providing a sciency description that just might appeal to some people. Something along the lines of this —
"Obsidian is primarily volcanic quartz that has cooled to produce this glass-like mineral. The light colored spots are natural cavities caused when gasses that were dissolved in the molten glass naturally form tiny bubbles as it cools (sort of like the bubbles you see in a carbonated beverage)."
I don't know. I think that the number of people who would find that appealing is pretty small.
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Post by rockjunquie on Jan 9, 2019 20:38:22 GMT -5
I’d be tempted to call them DESIGN ELEMENTS. 😀
That's funny, but also funny that you would suggest that! Rather than hiding them, I had thought about providing a sciency description that just might appeal to some people. Something along the lines of this —
"Obsidian is primarily volcanic quartz that has cooled to produce this glass-like mineral. The light colored spots are natural cavities caused when gasses that were dissolved in the molten glass naturally form tiny bubbles as it cools (sort of like the bubbles you see in a carbonated beverage)."
I don't know. I think that the number of people who would find that appealing is pretty small.
I can see that, but maybe something simpler like, a few tiny molten lava bubbles break the stone's surface in a few spots. I think I have seen them called surface features.
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Post by Pat on Jan 9, 2019 20:40:21 GMT -5
I’d be tempted to call them DESIGN ELEMENTS. 😀 That's funny, but also funny that you would suggest that! Rather than hiding them, I had thought about providing a sciency description that just might appeal to some people. Something along the lines of this — "Obsidian is primarily volcanic quartz that has cooled to produce this glass-like mineral. The light colored spots are natural cavities caused when gasses that were dissolved in the molten glass naturally form tiny bubbles as it cools (sort of like the bubbles you see in a carbonated beverage)." I don't know. I think that the number of people who would find that appealing is pretty small.
Too many words. Keep it simple. Same idea.
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Post by Deleted on Jan 9, 2019 21:13:56 GMT -5
I can see that, but maybe something simpler like, a few tiny molten lava bubbles break the stone's surface in a few spots. I think I have seen them called surface features. Sort of the same situation one comes across with rutilated quartz, some moss agates, limonite in topaz, etc. You can disguise, but nothing (apart from serendipitous lighting) really hides those little breaks in the polished surface. I admit to hating online photos when it comes to such materials - they magnify flaws that are all but invisible at normal viewing distances.
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Post by rockjunquie on Jan 9, 2019 21:18:30 GMT -5
I can see that, but maybe something simpler like, a few tiny molten lava bubbles break the stone's surface in a few spots. I think I have seen them called surface features. Sort of the same situation one comes across with rutilated quartz, some moss agates, limonite in topaz, etc. You can disguise, but nothing (apart from serendipitous lighting) really hides those little breaks in the polished surface. I admit to hating online photos when it comes to such materials - they magnify flaws that are all but invisible at normal viewing distances. I have cut many a stone that, to the eye, were absolutely fine. But, as I sell online, I knew they would never look good in a close up picture. So, they go in the gift pile.
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Post by opalpyrexia on Jan 9, 2019 21:43:31 GMT -5
Thanks for all of your advice and suggestions. I'm going to try the epoxy treatment and see how that goes. I'll post a before/after comparison photo to this thread. If it goes well I'll still need to work up a very brief dislosure of the treatment and the reason for it.
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Post by stephan on Jan 10, 2019 23:42:01 GMT -5
That's funny, but also funny that you would suggest that! Rather than hiding them, I had thought about providing a sciency description that just might appeal to some people. Something along the lines of this — "Obsidian is primarily volcanic quartz that has cooled to produce this glass-like mineral. The light colored spots are natural cavities caused when gasses that were dissolved in the molten glass naturally form tiny bubbles as it cools (sort of like the bubbles you see in a carbonated beverage)." I don't know. I think that the number of people who would find that appealing is pretty small.
Too many words. Keep it simple. Same idea. Agreed. Make it mystical. Talk about the "pristine 300,000 year-old air" (or whatever the number) inside the bubbles.
And as for the number of people who find that appealing being small... I bet someone once said that about enhydro agates ("How the heck am I going to sell agates with WATER inside them??! Sheesh.")
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Post by lpl on Jan 11, 2019 9:52:34 GMT -5
I'll be curious to see how the treatment with epoxy works out!
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Post by hummingbirdstones on Jan 11, 2019 10:00:17 GMT -5
opalpyrexia I don't know if this would work or not, but you could try filling them with Hxtal. Since it has a very close RI to glass, it may just blend those tiny pits right in. Just a suggestion.
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Post by opalpyrexia on Jan 11, 2019 12:26:22 GMT -5
opalpyrexia I don't know if this would work or not, but you could try filling them with Hxtal. Since it has a very close RI to glass, it may just blend those tiny pits right in. Just a suggestion.
Thanks for your suggestion, but most of them appear to have some white mineral lining portions of the pits. I examined them at 100X thinking that they could be crystals, which might have had some appeal for potential customers. Unfortunately the stuff just looks like white crud.
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Post by lpl on Jan 11, 2019 12:31:29 GMT -5
Does the white mineral stuff come off? I know once in a while I get small pits in things and there's a bunch of whitish material in them that's actually caked on diamond paste/cloth from the polishing wheel and I can get it off with a waterpik.
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Post by MsAli on Jan 11, 2019 18:26:24 GMT -5
opalpyrexia I don't know if this would work or not, but you could try filling them with Hxtal. Since it has a very close RI to glass, it may just blend those tiny pits right in. Just a suggestion.
Thanks for your suggestion, but most of them appear to have some white mineral lining portions of the pits. I examined them at 100X thinking that they could be crystals, which might have had some appeal for potential customers. Unfortunately the stuff just looks like white crud. Trapped Ash?
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Post by opalpyrexia on Jan 11, 2019 19:22:23 GMT -5
Thanks for your suggestion, but most of them appear to have some white mineral lining portions of the pits. I examined them at 100X thinking that they could be crystals, which might have had some appeal for potential customers. Unfortunately the stuff just looks like white crud. Trapped Ash?
Could be. I think that it might be some mineral that was dissolved in the obsidian, came out of solution as a gas as the obsidian gradually cooled, and then condensed out at an even lower temperature. Beats me what it is.
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