milfordman
starting to shine!
Member since August 2004
Posts: 32
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Post by milfordman on Dec 18, 2005 13:31:45 GMT -5
Enthusiasts:
I can not for the life of me get Obsidian to "wet shine." Most other gemstones I can polish to a wet shine with titanium oxide almost every time. I'm hoping someone here can help. I do the 60/90 until ready, 120/220, 500, 1000 AO, Polish, each for one week. The polishes I have tried so far are Titanium Oxide, Cerium Oxide, Tin Oxide. None of these get me much past a nice luster polish, but not the sought after wet shine. I'm going to try Aluminum Oxide Polish next.
Any ideas where I may being making a critical mistake? I have tried the same formula above for a 4 day cycle at 120/200 till polish. Any other polish I should try?
Happy Holidays to all,
MM
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Post by Alice on Dec 18, 2005 13:37:34 GMT -5
Have you tried throwing them into tripoli, then into polish? Sometimes it helps
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rallyrocks
fully equipped rock polisher
Member since November 2005
Posts: 1,507
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Post by rallyrocks on Dec 18, 2005 14:30:04 GMT -5
From what I've read here and am starting to catch from experience myself, "1 week" should really be considered more as a minimum duration, rather than a rule of thumb in any of the phases of tumbling.
Especially when dealing with hard rocks or challenging materials like obsidian, I'm finding that 2 week cycles are giving me more complete use of each grit, and I think that gets to be a critical aspect of the challenge approaching the pre-polish stages.
One other pesky aggravation is that some obsidian has tiny little gas pockets that release "larger than polish" sized shards, and I thinkk your best weapon against that is again going to be more duration in each phase leading up to polish.
Tumbling certainly is not an "immediate gratification" type of hobby- lessons take sometimes several weeks to learn "the hard way" it rewards patience. (a skill which I am not particulalry adept at myself)
I might add that I have yet to acheive the glassy finish on any of my obsidan, so maybe someone who has can call me on this...
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Post by LCARS on Dec 18, 2005 16:42:48 GMT -5
Obsidian isn't much different from beach glass & I had some trouble shining it at first as well.
I would recommend using as fine an A.O. as possible & then move to a high grade of C.O. polish to get a shine. If you go right from AO pre-polish to a fine polish you will be waiting a long time for it to eat all the fine scratches off the surface.
There may be other factors involved in your case that are affecting the finish as well. I'm sure someone with more experience doing obsidian will chime in with more advice... Good Luck! Hope it shines up nice for you!
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Post by Bikerrandy on Dec 18, 2005 17:31:36 GMT -5
Aluminum oxide seems to work on almost anything. The stuff that I get from the rock shed is great!
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Post by Cher on Dec 18, 2005 18:00:04 GMT -5
The obsidian that I've been tumbling was in coarse forever. I started it October 28 and finally moved it on Dec 8. It still didn't seem to have the smoothness that other rocks do coming out of 60/90 so I'm going to let it run longer in each stage. It's been in 120/200 for about 10 days now.
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Post by rockds on Dec 18, 2005 18:49:01 GMT -5
I'm doing tears right now and I skipped the 1st and 2nd stages and am doing a long 500 CS run to see how it goes. Was pretty happy with shape of the tears before they went in.
robert
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Pebbles
has rocks in the head
Member since November 2005
Posts: 557
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Post by Pebbles on Dec 18, 2005 19:21:04 GMT -5
MM -
I looked on the International Lapidary Assoc. Website and came across the following info. (Hope this may be of help):
"To tumble-polish Obsidian, do not use Cerium Oxide or Tin Oxide; these, being acidic, react with the obsidian, which is alkaline, and the best you can usually expect is a soft matte finish. (I can and have gotten good results with Tin Oxide using a very thick Tide (R) slurry, but that is because the TIDE is SO alkaline, it overcomes the weak acidity of the Tin Oxide. Don't rely on it; it takes a long time.
My best success has been with Raybrite (R), which is Aluminum Oxide, Octagon Process (R) liquid detergent, smashed Walnut shells, screened thru 1/8" mesh, and only enough water so that the whole mass will move. (I use a teaspoon!) Put it on and forget it for a week. (Unless you're using vibratory tumbler, which I don't recommend because Obsidian spalls like crazy unless you're using so much carrier that there is no chance for obsidian to strike obsidian) Open it up and look.
Here is the trick that very few people know. OBSIDIAN, ONCE POLISHED, UNPOLISHES READILY! So, once it has almost polished, look at it every hour or so until it has reached the shine you want. Turn it off at night. I know; that's a sin you're not supposed to commit, but if it's polished at hour 3, it would probably be unpolished by hour 8!
It's mighty persnickety stuff, but the results are worth the extra care. Oh - and pellets are a poor choice for carrier on obsidian; walnut shells or rice hulls work much better. Leather punchings are good, too."
Good Luck!!!
Pebbles
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Post by Cher on Dec 18, 2005 22:06:40 GMT -5
Thanks Pebbles, that's interesting.
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James
freely admits to licking rocks
Member since October 2003
Posts: 876
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Post by James on Dec 18, 2005 22:53:58 GMT -5
I'll tell you how I do it. It's actually very simple. I'd say that obsidian is the easiest stone to tumble. First if all, all the stones should be about the same size: 1-1/2" to 2" in diameter. They should be round in shape and have no sharp angles. This way the stones wont bruise.
Now that we've carefully selected the right rough, we can move on to the formula. Here it is. It is very basic, but it works. Put the stones in coarse grit for 1 month. Don't recharge. Don't even open the barrel. Just let them go for 1 month. Now, open the barrel and all the stones will be perfectly shaped and ready for 1000 ao. By leaving the stones in coarse for 1 month, you've allowed the grit to break down finer and finer eliminating to need for 120/220 or even 500 grits. OK, leave the stones in 1000 ao for 10 days with LOTS of plastic pellets. And finally, the last and critical stage. This is where most people fail. You HAVE to let to stones go in polish for 2 weeks. This is the key. Tin oxide is essential. Use LOTS of pellets!
I actually finished a batch of obsidian today. I will (weather permitting) post the pics tomorrow.
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stefan
Cave Dweller
Member since January 2005
Posts: 14,095
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Post by stefan on Dec 19, 2005 9:16:45 GMT -5
From the mouth of james- Seems like a great recipe-
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