danr
off to a rocking start
Member since October 2010
Posts: 1
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Post by danr on Oct 25, 2010 22:04:21 GMT -5
Hello, I am a "newbie" and could use some advice. My son and I bought a 6 lb. Lortone tumbler and have been working on our first batch of stones for a couple of months. It is a mix of quartz, jasper, agate and tiger-eye in varying sizes, but of similar hardness. We did a few one week stages of course 60/90 grit, one week of 120/220 medium/fine grit, one week of 500 pre polish grit, one week of 1000 grit (aluminum oxide) and finally one week of cerium oxide polish. We tried to be very patient and followed all of the steps carefully; the rocks seemed to be proceeding well. The polish step included a good quantity of plastic pellets. When we removed and cleaned the rocks after the the polish stage, we were disappointed to find that although the "faces" of the rocks were well polished, the "edges" of many of the rocks were rough. By "edges" I am referring to the thinner, radiused portions of the rocks. I have attached a photo of a sample piece of tiger-eye. I am wondering if the tumbler was too full and the rocks did not adequately tumble, or if perhaps the rocks scratched against each other. It seems that these rough edges are rougher than they were after the 1000 grit; we did not notice any differences between the faces and the edges of the rocks after the previous stages. We are not sure if we need to try to sort the rocks by type and tumble them separately; if we need to try again with less rocks in the tumbler; if we need to put them in the polish stage longer, etc. If just polishing the rocks longer will not work, which I expect that it will not, what stage do you suggest we go back to. Could we restart with the 1000 grit or the pre-polish stage, or do we need to go all the way back to the medium/fine grit? Any advice you can give would be appreciated. Thank you, Dan Attachments:
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revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
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Post by revco on Oct 26, 2010 3:01:47 GMT -5
That almost looks like undercutting, but if it's been incredibly consistent amongst all the rocks, I'd say that's not very likely.
Did you take care to insure that there were no broken rocks before moving into polish? Anything with really fine edges? (I toss anything that may be risky in polish.) Did you have a good amount of small rocks in the mix?
Usually too full is better than not full enough, but there can be some undesirable effects from an overloaded barrel. The aim is to get right around 2/3 total, as close as possible, to promote a proper tumble. Usually I use somewhere around 3-6 tablespoons of pellets in polish...more, if required, to get to 2/3.
I haven't tumbled that specific combination of rocks, but I do heavily mixed loads on a regular basis and while I have some oddballs, most turn out well. I use nearly an identical process as well. I don't really see anything wrong with your mix, so it would probably be a last ditch effort to separate them.
Based on the picture, I would probably say that you need to look at 500 again, mainly because you need to remove a little bit of rock to clean them up. Your 1000 may do it over a couple weeks as well and could save you a step, albeit not much time.
Hope that helps and you find out what's going on!
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Post by tanyafrench on Oct 26, 2010 6:17:06 GMT -5
On many hard stones I have recharged the barrel in coarse 4 or 5 times (weeks). I check each stone before moving it on to 120/200. If the stones are pit free and looking smooth then they get moved on but not before. When I first started my goal was to move the whole load forward but discovered I can't always do that. You can use plastic or ceramic pellets to complete the load as the stones get reduced. This may help. Welcome to the RTH. We try to answer questions and you won't find a better source. I am also fairly new but there is some real experience on this board.
Tanya
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Post by johnjsgems on Oct 26, 2010 6:44:25 GMT -5
The last step (after polish) should be a burnish (wash cycle) with borax, Tide, or another powdered detergent, If only the tiger eye looked like that it could be a polish residue. Tiger eye is an agate replacement of asbestos so can be fibrous. When cabbing it will often break on a fiber line. If other types of rock are also "beat up" looking on outer edges I would rerun the batch in 500 and examine them after rinsing and letting them dry. You may want to use a magnifier. Rocks are tricky by nature and will hide scratches when wet so they show up after polish stage. This is true of tumbling, cabbing, etc. Good luck.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Oct 26, 2010 9:13:10 GMT -5
Other than with rocks that will "fiber out" regardless [some tigereye], or are somewhat porous, our experience is that we didn't use enough cushioning in the polish and soap burnish cycles.
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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 Oct 26, 2010 17:51:59 GMT -5
Tiger eye is famous for that problem especially in a rotary tumbler which knocks rock together a lot. You have to use lots of plastic pellets and it's best to have the stones spend a long time in rough grind and get the edges well rounded for best results...Mel
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Post by deb193redux on Oct 28, 2010 14:31:33 GMT -5
You can test to see if this effect is there before polish by rubbing a little polish slurry on the rock. In some cases, these imperfections only show up when the very fine AND white polish gets into the imperfections.
Quartz and tigereye is more likely to craze on edges. DO you have a pic of a piece of jasper that did this?
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arniflor
off to a rocking start
Member since December 2011
Posts: 2
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Post by arniflor on Dec 4, 2011 12:17:59 GMT -5
Have you found an answer to your question? I have the same problem and it is driving me crazy. I use beach stones that are very flat. They look fine until they come out of the polishing stage and then the edges are very rough and look horrid. If you have found a solution I would appreciate to hear about it.
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Dec 4, 2011 22:23:33 GMT -5
Greetings Ladies & Gents, a simple test to check if a stone is ready for polishing is by just dipping the stone in water, then take it out again and look at the stone. Question: Does the water bead on the stone? Yes, it is ready for polishing. No, it still needs further fine grinding. -- I hail from (The Barony of Seabegs) Bonnybridge, Stirlingshire, U.K, where aliens (15mb) sometimes come for a visit & about 4 miles west from this monstrosity! Sticky's: their contents are resource information 1#: Vendors worldwide (2mb), 2#: How to use the forum, 3#: How to identify rocks & minerals, 4#: Save money on expensive grits & polishes!
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arniflor
off to a rocking start
Member since December 2011
Posts: 2
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Post by arniflor on Dec 8, 2011 13:31:46 GMT -5
The problem is directly around the edges. Your water test is a great tip for in general. It is more difficult to test the edges in this way. The stones appear to be perfecly ready. One puts them through the polishing stage. They come out very shiney as they should but not around the edges. Once they are polished this is very clear, it does not seem detectable before then.
My question is for anyone who has experienced this particular problem and has found the solution.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Dec 8, 2011 22:35:25 GMT -5
Based on having the same problem, and still occasionally do, I think you aren't padding well enough in the polish stage. Seems some rocks will "rough edge" no matter what, especially flat ones. We use lots of air shot pellets, heavier ones that don't float, and chunks of leather about 1 to 1 1/2" square in the polish stage. The leather being about 20% of the load. Some people like using leather, some don't, works for us.
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 9, 2011 1:23:29 GMT -5
As already explained, some stones, like tiger eye, have long fibrous crystals. The important characteristic though is that fibers are all oriented (more or less) in one direction. Other stones, like any of the feldspar group, often cleave along planes corresponding to their crystalline faces. Both of those kinds of stones have an x, y and z orientation to them. Their surface characteristics are not the same in all directions. Stones like that will respond to tumbling (or any kind of polishing) differently in one direction, than another. In some directions they polish just fine, in other directions they are prone to undercutting, for example. Was that helpful? : -)
No? OK, what they said. It's the cushioning (I think).
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billg22
spending too much on rocks
Member since November 2011
Posts: 451
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Post by billg22 on Dec 9, 2011 1:32:21 GMT -5
That's interesting about leather. Can you cut up an old belt?
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bushkraft
having dreams about rocks
Public nuisance Number 1
Member since July 2011
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Post by bushkraft on Dec 9, 2011 2:51:23 GMT -5
That looks like a chunk of Brockman material, I make 3 or 4 cabs a day from Australian tiger eye ( including marra mamba) and it is quite usual for some areas to be softer than others, the trick is to test it on a grinder before working on it ( I use 50 grit for this) or alternativly hold it against the edge of a saw blade, the degree of silcification within a stone can change from a nice hard 7 down to perhaps a 3 within a few milimetres, sometimes I find a pocket of pure crocidolite dust which is not only annoying but also a bit unnerving.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Dec 10, 2011 21:55:35 GMT -5
In response to billg22, we get our leather at garage sales, etc. anything cheap will work, leather is leather. We do avoid really thin split leathers [process eats it up], and have found dyed mtls. will sometimes discolor the liquid, but have never dyed our rocks. Were one to use heavily dyed leather to pad some fairly soft and absorbent mtl. I suppose the rocks might get colored up.
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stefan
Cave Dweller
Member since January 2005
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Post by stefan on Dec 12, 2011 10:14:34 GMT -5
Just some thoughts. I have never had great luck with Cerium Oxide. Try as I might it just does not work well for me. I use Alum. Oxide, Titanium Oxide or Tin Oxide. Another thing is that all of my polishing cycles run for 3 weeks. New polish seems to need a break-in period. I always save my used polish and add a 50/50 mix (new/old) when running a batch. I liked your 60/90 cycles, but I tend to run all other stages for 2 weeks instead of 1 (no recharges), then of course the 3 week polish cycle. Also with a single barrel tumbler you gotta be EXTRA careful about cross contamination. THe first tumble is usually the most difficult!
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