Fossilman
Cave Dweller
Member since January 2009
Posts: 20,666
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Post by Fossilman on Nov 3, 2020 11:18:25 GMT -5
I have never had good luck running Obsidian in a rotary tumbler (twice)... Just doesn't bring up the shine Obsidian can do.. The best shine and polish are with a Vib tumbler... A buddy of mine is a beginner on a Vib and he nailed the polish to a T, from a recipe on this forum, that he followed... One day I might tackle Obsidian again, but for now - NOPE!
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Post by taylor on Nov 3, 2020 12:04:28 GMT -5
Your pictures reminded me of our experience running obsidian. After a couple of fails we sorted the obsidian more carefully and got super results. In our case we removed the mahogany obsidian and the opaque obsidian from the rest. We are running rotary and used cerium oxide to polish. We do use plastic pellets. The pellets are dedicated to a "grit." For example one set is used in 600, another set for cerium oxide, and another set for "clean after polish." Good luck!
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Post by Bob on Nov 3, 2020 16:06:15 GMT -5
Wow. Thanks to all of you for tips. It appears that it's not enough to just do obsidian and man-made glass separately, but even within those categories to separate types potentially! I did notice with my glass that some was nearly shiny and some was terribly frosted and some in-between. And those results are not random, the are associated with different types/colors of glass.
Oh man, this adds a whole new level of complication. Well, I'll try that and at least don't have to worry about wasting polish if I don't have a full load becasue I recycle polish anyway. And, I'll just make sure to fill out the load with plastic pellets. And if they don't work, I'll use ceramics. I only have a cup full maybe of those tiny ceramic beads. The owner of the Rock Shed told me they need not be prepped in any way before using in a polish run--but the thought of doing that makes me a bit nervous.
I think I'm going to wait until a few months from now to try again because it will take that long to get all my obs and glass through pre-polish. I also have some obs that it too large for a 12lb barrel and it's current in my saw pile. I'm going to move it up in priority and try to saw it in half this weekend and get it in processing also. Probably after eventually nailing this I'm going to shift back to other material for a few years! This is a royal pain.
It may be easier in a vibe, but I've seen both obs and glass done in a n old timer's tumbler that has a shine like no other. In fact, it's probably the most fantastic shine I've ever seen.
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Nov 3, 2020 18:13:15 GMT -5
I didn't have any trouble mixing obsidian types. I had mahogany, silver sheen, firework, snowflake, purple sheen, and plain old transparent and opaque stuff in my last successful batch. I may have been lucky on that batch, who knows. But I did run it with that little quartz and was disappointed, then ran it the same way without that lil bugger and made out like a bandit.
Every source varies though. I can see obsidian from one place having problems and another source being relatively "easy". Just like tiger eye having problems with fibers and amethyst chipping to kingdom come sometimes.
Glass varies a LOT. I decided not to tumble any more glass after my first success. It's infinitely more picky than obsidian if you ask me! If I did tumble glass again it would be one piece of glass in a sea of ceramic. It would have to be a really nice piece, also. Not just a shard of a beer bottle.
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Post by Bob on Nov 5, 2020 11:19:22 GMT -5
On that amethyst chipping to kingdom come...
I kept buying amethyst from different sources, and from different countries of origin thinking I was getting poor, fractured quality. But, after a couple of years I finally figured out that it appears to be the nature of the beast for it and smoky and rose quartz unless one were to buy gem quality. I did buy a small amount of almost that quality of Uruguayan amethyst once--it's pale purple but very uniform and clear, but fractures easily too so has to be dealt with very gently.
Finally I resigned myself to the following methods and for 2 years now doing this has allowed me to build up enough nice in pre-polish or almost all there. I tumble those only with themselves, or with glass or obsidian if I have any. I even do media filler in rough grind 50-70! I use previously rounded large ceramics. And, I really go after it to get the bad spots out, which can sometime take MONTHS! It common for me to grind away 50% of the starting size in this stage, especially for that chevron amethyst blades. Then, in 80, I almost always do more than 1 week to get those final fine cracks out, and also 50% ceramics. At this stage, you sometimes see that angering effect of grit going into some fractures, but that I've found really happens in 220 a lot.
At night, shining a very bright flashlight into the pieces has helped me at this point figure out those that ought to be cleaved before going on.
Before 220, I Opticon to help block those fine fractures, and run 220 until I believe either the fractures are gone or they will not leave because they just keep going. But, my success in prep has come from the pain of doing Opticon between EVERY batch starting with 220 all the way to pre-polish. Yes, that takes a while, but it works. I'm guessing that it might strengthen the upper edges of fractures. Then 600 and then 1,000 prepolish, and then Opticon one-last time before polish.
I've been tumbling for 6 years and frustrated that I don't yet have a big bowl of gorgeous tumbled amethyst, and smoky and rose quartz. But that last 2 years and all that work is leading up to me making some wonderful polish runs with it in the next few months. Then I'm going to stay away from it for a while! Just last night, I had another 6lb batch of smoky quartz and rose and rock crystal make it through pre-polish. The rose quartz almost glows--apparently something is going right with it and maybe it's that the refractive index of Opticon matches that of crystal quartz so as many of the internal fractures that it can reach almost disappear.
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Post by Bob on Nov 30, 2020 18:01:14 GMT -5
Well, I just had a 12lb barrel of amethyst, rose quartz, obsidian, and glass complete 80 grit with about half being large ceramic pieces for cushioning and no plastic beads. I like what I see. It was done in a week, whereas in cold weather this time of year it normally takes 8-10 days for it to reach this point with half plastic beads and need a recharge.
One question that always bugs me is which did I grind more, the rocks or the ceramics? Probably both the same as they are all in effect rocks. But with the plastic beads, I don't think they get ground much if at all, because even a year later they stay about same size.
Also, the ground surfaces of the rocks seem just a little better to me than had there been only plastic beads. It looks to me like just more got done--not a lot, but a little. One rock is a rose quartz a bit larger than a large lemon and the surface looks like more progress was made than in 2 runs with plastic beads.
So I'm going to take this all the way and see how it goes, but still change to plastic beads when I run the polish. Thanks for all for the strong suggestions to switch to ceramics for this material.
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Nov 30, 2020 18:16:53 GMT -5
If it was me, Bob, I would run ceramic all the way. Then you'll have your load of polish-only ceramic ready, and I believe you will probably say the polish is better than with plastic beads.
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Post by Bob on Nov 30, 2020 18:21:14 GMT -5
Might do that Eric. Probably would be able same as if I used some of my many polished smalls. It just amazes me how many different approaches we all take. Sure makes it fun to talk about! I had a recent batch of this material complete alum ox (to compare to prior one with cerium ox) and will post photos soon.
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