waterboysh
spending too much on rocks
Member since April 2021
Posts: 386
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Post by waterboysh on Feb 28, 2022 13:04:58 GMT -5
Recently I purchased some Mahogany Obsidian, Midnight Lace Obsidian, and some Apache Tears. The Mahogany came in multiple big pieces and I was pretty successful using my Dremel to score all the way around it and then break it with a chisel and hammer. So now the Mahogany is a more manageable size (I think anyway). You can see the pictures here. The Midnight Lace came in a single 1.5lb chunk and was to thick to make any noticeable dent with the Dremel. So I just took a hammer to it and smashed it into smaller pieces. Most of the smaller pieces were still to big, but were small enough to now score with the Dremel. Unfortunately, I forgot to take a picture and these are now tumbling in 60/90 in a 3lb barrel. Anyway, I had a small handful of shards that I thought would be to thin to put in the rotary, so I put them in the Lot-o. I ran them through 120/220 in the Lot-o for 3 days and the sharp edges rounded off pretty well. Then I ran them through 500 AO and then AO polish for 2 days each. This is how they turned out.     Initially, it looked like they had turned out good. When I hold them up to the light, the frostiness you can see in the pictures is less noticeable, but it's very hard to get a good picture like that. It wasn't until I set them down I realized they have a slight frosty glaze across the whole surface. For media, I was using aquarium pea gravel. I thought I had a picture of it somewhere, but I don't seem to. Everything seemed to go pretty well, so I was a little disappointed when I saw the haziness, and I'm not sure what I can try changing. |
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Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,512
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Post by Brian on Feb 28, 2022 14:05:38 GMT -5
It looks like you got them just the right size to show off the transparency without losing some of the color.
I’ve only tumbled a few pieces of obsidian. It’s neat material and I have a whole lot more the work with when I get the chance. Most of mine are large pieces so I’m glad to hear the Dremel and chisel worked out well (in case I don’t feel like dragging out the tile saw).
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waterboysh
spending too much on rocks
Member since April 2021
Posts: 386
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Post by waterboysh on Mar 1, 2022 11:40:58 GMT -5
For reference, here's what my media looks like  |
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nursetumbler
Cave Dweller 
Member since February 2022
Posts: 992 
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Post by nursetumbler on Mar 1, 2022 11:42:15 GMT -5
The Obsidian I picked up out here in New Mexico on the side of the road is bloudy. I spoke with a native at the local rock shop and she said i shouldn't believe in pure Obsidian. She said it was lava flow that created it so as the lava moved and cooled past melting the silicait continued to pick up material in it. I dont know how true that is but thats what the lady told me. Maybe run it through prepolish and polish again but longer. I don't really know for sure because I havent polished mine yet. 🤷♀️
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hnhstngs
noticing nice landscape pebbles
Member since September 2018
Posts: 93
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Post by hnhstngs on Mar 3, 2022 13:38:30 GMT -5
I have a different rough grind process but finish all my obsidian in a vibe as well (UV3 not a Lot-o). Couple of things you could try - First, add a 1000 AO step between the 500 AO and polish. Obsidian is soft and I've seen better finishes with smaller "steps" between grit. I also use a 600 SIC step before I go to the 500 AO but that is in a rotary tumbler. Second, have at least 50% of the volume of the tumbler be media. I used to get lots of surface "bruising" in the polish stage before I started doing this. Stone would look pretty good before going into polish but afterward I'd see all these tiny little fracture marks when looking at the stones through a 10x loupe. I also started adding a Tbs of sugar to my "slurry" mix in the vibe to make the stones stick together a little and not bang around so much. Got that one from reading posts from jamesp. He's done a lot of work with glass and his finishes are my gold standard. |
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,717 
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Post by Fossilman on Mar 3, 2022 13:48:16 GMT -5
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,589
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Post by jamesp on Mar 5, 2022 10:33:32 GMT -5
hnhstngsSome people seem to have problems running sugar in their Lot-O. As if they have different actions. they may bog down.. My Lot-O can final polish glass with a perfect polish but I have only used Borax in the Lot-O on glass and OB. I have a modified Vibrasonic that can really move a thick sugar slurry easily and gets all steps done quickly. Glass and obsidian can be a real quick tumble if the vibe is tuned for it. Well, the well tuned vibe is my theory anyway. The finer the abrasive the easier it is to bruise the surface in my experience. Polish is the step that has to be done gently to avoid 'micro-bruising', however any bruising done from prior steps can not be removed with polish. So the problem can be complicated. I see people using other abrasives like tin and cerium oxide. Aluminum oxide does a great job on polishing glass/OB. That is a fact. Use 50% tumbled quartz pea gravel(like the photo above) and do not tumble anything bigger that 20 grams. A single 30 gram chunk of glass or OB in the batch starts to bruise the edges of my glass/OB. I magnified this photo so the surface can be seen clearly. The white spots are bubbles in the glass, not bruises. And this glass is crystal clear which makes it much easier to see bruising/hazing/frosting or whatever word used to describe impact damage. And this is a softer glass, soda lime, hand blown. Glass and obsidian vary in hardness quite a bit. Mahogany obsidian is by far the hardest obsidian i have ever tumbled. The softests was grey/black obsidian. It must be iron in Mahogany that hardens it.  This is cast glass. Not blown. It is the softest of the art glass that I have ever tumbled. If the slurry is not managed carefully it will have to be redone in say AO 220. Basically start over with finish steps. It was cast with all kinds of decorative garbage in the glass. The upper right piece has copper wires in it. Where the wire exits the glass it always chips there. 
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,589
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Post by jamesp on Mar 5, 2022 10:43:04 GMT -5
For reference, here's what my media looks like Excellent media for obsidian. Best to run 50% with obsidian. |
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Post by broseph82 on Mar 9, 2022 12:51:18 GMT -5
Recently I purchased some Mahogany Obsidian, Midnight Lace Obsidian, and some Apache Tears. The Mahogany came in multiple big pieces and I was pretty successful using my Dremel to score all the way around it and then break it with a chisel and hammer. So now the Mahogany is a more manageable size (I think anyway). You can see the pictures here. The Midnight Lace came in a single 1.5lb chunk and was to thick to make any noticeable dent with the Dremel. So I just took a hammer to it and smashed it into smaller pieces. Most of the smaller pieces were still to big, but were small enough to now score with the Dremel. Unfortunately, I forgot to take a picture and these are now tumbling in 60/90 in a 3lb barrel. Anyway, I had a small handful of shards that I thought would be to thin to put in the rotary, so I put them in the Lot-o. I ran them through 120/220 in the Lot-o for 3 days and the sharp edges rounded off pretty well. Then I ran them through 500 AO and then AO polish for 2 days each. This is how they turned out. Initially, it looked like they had turned out good. When I hold them up to the light, the frostiness you can see in the pictures is less noticeable, but it's very hard to get a good picture like that. It wasn't until I set them down I realized they have a slight frosty glaze across the whole surface. For media, I was using aquarium pea gravel. I thought I had a picture of it somewhere, but I don't seem to. Everything seemed to go pretty well, so I was a little disappointed when I saw the haziness, and I'm not sure what I can try changing. Not enough time in your lot-o. Once you move to 500g go 3 days and polish try 4 days. Also, with obsidian less grit is more. Only use 1/2-1/4tsp of grit and or polish |
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waterboysh
spending too much on rocks
Member since April 2021
Posts: 386
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Post by waterboysh on Mar 9, 2022 13:20:46 GMT -5
The finer the abrasive the easier it is to bruise the surface in my experience. Polish is the step that has to be done gently to avoid 'micro-bruising', however any bruising done from prior steps can not be removed with polish. So the problem can be complicated. I see people using other abrasives like tin and cerium oxide. Aluminum oxide does a great job on polishing glass/OB. That is a fact. Use 50% tumbled quartz pea gravel(like the photo above) and do not tumble anything bigger that 20 grams. A single 30 gram chunk of glass or OB in the batch starts to bruise the edges of my glass/OB. , when you say nothing larger than 20g are you talking about the weight when it starts off in the Lot-o or the starting weight before running in coarse? I just went and checked several of my chunks of mahogany obsidian and they are all anywhere from about 60 - 100g. Should I try to cut them down smaller with my Dremel before I start tumbling them? |
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Tommy
Administrator 
Member since January 2013
Posts: 12,936
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Post by Tommy on Mar 12, 2022 23:29:59 GMT -5
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,589
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Post by jamesp on Mar 13, 2022 9:48:03 GMT -5
The finer the abrasive the easier it is to bruise the surface in my experience. Polish is the step that has to be done gently to avoid 'micro-bruising', however any bruising done from prior steps can not be removed with polish. So the problem can be complicated. I see people using other abrasives like tin and cerium oxide. Aluminum oxide does a great job on polishing glass/OB. That is a fact. Use 50% tumbled quartz pea gravel(like the photo above) and do not tumble anything bigger that 20 grams. A single 30 gram chunk of glass or OB in the batch starts to bruise the edges of my glass/OB. , when you say nothing larger than 20g are you talking about the weight when it starts off in the Lot-o or the starting weight before running in coarse? I just went and checked several of my chunks of mahogany obsidian and they are all anywhere from about 60 - 100g. Should I try to cut them down smaller with my Dremel before I start tumbling them? Yes. I can't avoid bruises on such large pieces but that's my experience. A broad mix from 6 to 20 grams works best for me. |
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