wi54880
starting to shine!
Member since March 2009
Posts: 33
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Post by wi54880 on Sept 21, 2010 23:09:59 GMT -5
Should I have used something besides AO on these? The are perfectly smooth after going through all the cycles, everything else in the batch looks great, but these are just dull!
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Post by connrock on Sept 22, 2010 5:29:42 GMT -5
I don't think it's the AO,,,,,,
when you say "everything else in the batch looks great but these are dull"
This makes me suspect that you are mixing obsidian (Apache Tears) with some other type of rock(s)?
Obsidian should be done alone and also with a bit of care as it will chip and crack easily.
When obsidian is done in a rotary plastic pellets are used as a cushion in all of the stages after they are roughed in and in. Separate pellets are used in each stage to prevent cross contamination of the various grits and of course the polish.
If you haven't mixed different types of rocks in this load then there's another problem we'll have to address.
Hey,,,,ya gotta start somewhere??
connrock
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,466
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Post by Sabre52 on Sept 22, 2010 7:10:03 GMT -5
I haven't had a lot of luck with tears myself but a buddy of mine over in Gatesville, TX has been experimenting around and just sent me a sample he had finished in his UV-10 vibe. They were the best tears I've ever seen polished. After coarse grind, he put them in 220 for a few days with ceramic beads as filler, then ran four days each in tripoli prepolish and tin oxide polish with lots of plastic pellets for a buffer. He as conn has said, ran them alone, just tears with no other rock and they had a perfect mirror shine when done.....Mel
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chassroc
Cave Dweller
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
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Post by chassroc on Sept 22, 2010 8:11:19 GMT -5
Some TLC needed but they should shine like Glass(ha ha).
I also use plastic pellets after coarse grit stage. Washing more carefully between stages might have merit with these.
I use 1000AO between fine grit and polish.
I believe I use AO for polishing Apache Tears... when I have doubt I try Tin Oxide next.
Charlie
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Post by johnjsgems on Sept 22, 2010 9:06:04 GMT -5
Somewhere around here is a coffee can with my attempt at Apache tears. They looked better before I did them. All of the advice above will get you there. I'm tempted to find mine and try again. They were back in my beginner days. The best I've seen finished in a rotary were polished with cerium in Karo syrup. The best obsidian I've seen finished in a vibe were polished with Myers Rapid Polish with ceramic media as cushion. Good luck. Obsidian is probably the most frustrating material for beginners.
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wi54880
starting to shine!
Member since March 2009
Posts: 33
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Post by wi54880 on Sept 22, 2010 9:43:52 GMT -5
I did have them mixed with some other rocks, so maybe that was my problem. They still feel smooth, so how far back should I go in the process? I have plastic pellets lying around somewhere too that I can throw in with it. Thanks for the advice, hopefully they turn out better because I've seen some pretty great pics of them all shined up!
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Post by 150FromFundy on Sept 22, 2010 9:44:06 GMT -5
Everything you need to know has been answered. Obsidian is both soft and brittle. It is a rock for the "advanced", rather than the "beginner", and is a good test of even a veteran tumbler's skills.
Remeber: (1) separation (no other rocks) (2) pellets (25% to 50% of the load) (3) additional stage (1000F as a pre-polish) (4) additional burnish (between every grit/polish change)
It's a simple recipe. If you carefully follow all the tips & tricks, it will work for you.
Darryl.
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Post by susand24224 on Sept 22, 2010 10:52:06 GMT -5
Now that you have all the proper methods down, I will throw a wrench in. Absolutely tumble with nothing else, though. I successfully tumble Apache Tears doing the following: 1. 50% ceramics in each stage. 2. A run in 1000 3. Borax added as a thickener, Ivory would probably work as well. 4. I polished successfully with AO from the Rockshed (NOTE: all AO is not created equal), but it took about three weeks in polish in a rotary. Also, the ceramics and thickener are to prevent chipping, etc., but the shine should still be there without them. Susan
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wi54880
starting to shine!
Member since March 2009
Posts: 33
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Post by wi54880 on Sept 22, 2010 11:03:33 GMT -5
I'll be honest, I don't really understand why they'd have to be left alone to polish them, but I have only been polishing agates up until now. I have about 70 pounds of random stuff that is finally done with the first three stages, so hopefully I don't run into anymore snags when I start polishing them this fall.
But, if I do, I'll be back!
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chassroc
Cave Dweller
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
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Post by chassroc on Sept 22, 2010 11:27:52 GMT -5
Agate and Pet Wood are relatively easy to shine.; They are hard( and even the petrified wood by the final stage) and durable and take a wicked shine. The softer the rock, the harder it is to shine, especially in mixed batches.
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Post by susand24224 on Sept 22, 2010 13:20:39 GMT -5
To respond to your question about why they need to be tumbled alone:
There are several factors that affect how rocks tumble. One is the hardness, and I think Apache Tears are Mohs 6.5 or harder, but would appreciate correction if I am wrong.
The second factor is how brittle the rock is. Apache Tears are *very* brittle. Other "brittle" rocks are some crystalline quartzes and the dreaded tumble for me, which is turquoise. Brittleness causes internal fracturing, spalling, and chipping, although other things can cause this as well.
In a perfect tumbling world, we would only tumble one type of rock at a time, and even more perfect, that rock would all be from the same location. Most rocks give us a fair amount of margin of error, though. Agate has a huge margin of error. Apache Tears do not. I don't even tumble them with obsidian, although I have seen a few photos here of people that did and they turned out quite well.
I have a "mixed Mohs 7" tumbler going constantly. I always get a few that don't polish the way that I would like. I save these, and when I have a barrel full, tumble them alone. Most of them respond to this. I don't remember any agates going this extra step.
Susan
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Post by jakesrocks on Sept 22, 2010 14:05:13 GMT -5
Susan, Obsidian ( Apache Tears ) vary from Mohs 6 to 7. Most being on the softer end of the scale. They are very brittle. The first batch I tumbled, it took me over an hour with tweezers and my OptiVisors to get all of the splinters out of my fingers. They should only be tumbled by themselves with lots of pellet filler, and are best done in a vibe. Don
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Post by Hard Rock Cafe on Sept 22, 2010 14:54:28 GMT -5
In lay terms, when you polish softer rocks with harder rocks, the harder rocks will polish, but the softer ones will just wear away. That's why you need to separate them.
Chuck
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