Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 12:21:13 GMT -5
Hello,
The title says it all. I am having a terrible time with tumble batches going just fine all the way to the polish stage, and then during polishing the batch self destructs in a spectacular way. The damage is impact related and turns all the edges white and in some cases covers the stones with actual pock marks like pieces were chipped out in a small hole making tiny pockets all over.
I had this problem a while back when I was tumbling only glass cullet. It took a lot of trial and error but I finally figured out a formula that worked. I have been using that formula in a longer version now for jasper's and quartz's. I have had great successes with yellow aventurines and apatite and fancy jasper where I used my formula and everything went perfectly all the way to high gloss, and the glass still works perfectly.
But some batches just "decide" that suicide is the way to go and everything goes south at the polishing. The most recent blow-out was a batch of mixed "premium" stones. All the stones were Mohs 7; a mix of amethyst, clear quartz, jaspers, sunstone, and others I don't recognize. The batch was looking great between all stages. I followed the formula for the polish and WHAMO! Garbage out.
I am using a Lortone QT66 (two 6 pound barrels) and a severely modified Chicago Electric with two 3 pound barrels. The QT66 barrels are loaded with 2 pounds of stone per barrel and media up to about 1.5 inch from the top. Water filled to just under the top layer of media. In the CE I use one pound of stone per barrel and media up to about 3/4 full. Water filled to just under the top layer of media. When the damage happens, it happens the same way on either machine.
Mohs 6 to 7 Tumbling Formula:
1: 60/90 Carbide Grit, Large Ceramic Media, run for 6 to 8 days 2: 120/220 Carbide Grit, Large Ceramic Media, run for 6 to 8 days 3: 500 Carbide Grit, Large and Small Ceramic Media, run for 6 to 8 days 4: (Optional) 1000/1500 Carbide Grit, Large and Small Ceramic Media plus X shaped Plastic*, run for 6 to 8 days 5: Aluminum Oxide Polish, Large and Small Ceramic Media plus X shaped Plastic*, run for 6 to 8 days
* The X shaped plastic is those little spacers that are used for setting the spacing when laying tile. I buy the 1/8 inch size.
The above formula in very short rough grit run times works great for glass cullet. The run times shown above work well for Mohs 5 to 7 stones. Forget calcite. I can't seem to do that at all. It's just too soft at Mohs 3. It either wears away to nothing, or turns to frosty snow balls on polishing, usually both.
Grit Amounts:
For the QT66 barrels I use 5 to 6 tablespoons of grit. For the CE barrels I use 2 to 3 tablespoons. In all cases I add 1/4 cup of Borax to suppress gas buildup.
Before anyone suggests it, I cannot use a vibe tumbler for polishing. I live in an upper apartment and I couldn't isolate the noise well enough. The rotary tumblers I can isolate to near silence.
Okay, all that said, can anyone think of why some stone batches spontaneously go bad on the polish stage while others work perfectly?
I have had a suggestion to use corn-cob media and run the polish dry, but all my experiences with trying to run anything dry in a rubber barrel have been bad. Usually both the material and media end up coated in black rubber and a total loss.
Any help here would be appreciated.
Thanks, -Jim-
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Post by captbob on Aug 13, 2015 12:36:13 GMT -5
Can you post pictures?
You are getting Mohs 7 stones shaped in 6 to 8 days??
I'd pull ceramic media from your polish stage and go with strictly plastic filler. Fill barrel darn near to the top when polishing. You want to lessen the extra room to reduce the tumbling action. If you can hear the rocks tumbling in the polish stage they are dying in there.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 13:07:57 GMT -5
The damage is pretty had to photograph well, but ... This is just a few ... The ones circled show the most obvious impacts, and as a whole these now look like I just picked them out of a river. That wasn't the case. Before polishing they were smooth and beautiful when wet. The little one below the green stone on the left is sunstone and now it looks like a snowball. The green one on the left (don't know what it is) was all sparkly before. The real bummer is that every time I have to backup to 500 grit to remove the damage the batch gets smaller and smaller and smaller ...
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 13:11:51 GMT -5
Yes, I tend to like them to be closer to the original shape. I only tumble them to round by accident. LOL ... I did that with apatite by running the 60/90 too long since it's a Mohs 5. I converted 1 pound of stones into 9 ounces in one 60/90 run of 8 days.
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Post by johnjsgems on Aug 13, 2015 13:18:13 GMT -5
Very strange. I quite often get the same question from beginners that let their barrels run lower through the stages until they have half loads by polish. Then they get the frosting, pitting, etc. Are the rocks completely smooth before polish? Looks like fissures to me. Maybe not long enough in coarse to completely smooth rocks and carrying grit along in those fissures. Seems like the rocks are hard enough to use ceramics with no problem. Unless your ceramics are metal finishing ceramics with abrasives (would be grey or other than white).
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Aug 13, 2015 13:23:43 GMT -5
You have to dry the rocks out every step and inspect them for frost damage like that. Can NOT be seen when wet. Especially quartz like the ones you are tumbling enigma. Agate hardly frosts, crystalline quatrz like that will much easier. captbob made a fine suggestion. Your rocks have been hitting too hard.
To fix that you need to wear off the frost damage. Guessing a week in your 120/220. And then your 500/1500/polish. Some may go all the way back to 60-90. Probably better. Yes, bad news.
I tumble a lot. About happy just doing bulletproof agates and jaspers and petrifications. Life too short. Those crystalline quartz's require at least a fuller barrel like 80%, and padding like captbob suggested in polish mode. Then they are easy.
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Post by adam on Aug 13, 2015 13:46:01 GMT -5
Well, maybe the stones can't be polished anymore? Is there such a thing as too much aluminum polish? Perhaps. I re-tumbled a certain batch of jaspers and agates and they didn't seem any better than before.
I hope you find your answers here.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 14:44:30 GMT -5
Are the rocks completely smooth before polish? Looks like fissures to me. Maybe not long enough in coarse to completely smooth rocks and carrying grit along in those fissures. Seems like the rocks are hard enough to use ceramics with no problem. Unless your ceramics are metal finishing ceramics with abrasives (would be grey or other than white). I completely remove and wash the stones and clean out any fissures or grit traps and inspect them dry before moving on. By the end of the 500 or 1500 stage they are very smooth with no evidence of damage at all. On some stones it looks like they get fully polished and then the edge damage happens late in the run. The polished sides look like a coating of plastic that is peeling near the edges.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 14:47:22 GMT -5
You have to dry the rocks out every step and inspect them for frost damage like that. Can NOT be seen when wet. ... Your rocks have been hitting too hard. I completely remove and wash the stones and clean out any fissures or grit traps and inspect them dry before moving on. By the end of the 500 or 1500 stage they are very smooth with no evidence of damage at all. It puzzles me that there is never any damage in earlier stages, only ever happens in the polish stage.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Aug 13, 2015 14:54:13 GMT -5
You have to dry the rocks out every step and inspect them for frost damage like that. Can NOT be seen when wet. ... Your rocks have been hitting too hard. I completely remove and wash the stones and clean out any fissures or grit traps and inspect them dry before moving on. By the end of the 500 or 1500 stage they are very smooth with no evidence of damage at all. It puzzles me that there is never any damage in earlier stages, only ever happens in the polish stage. Good that you know that it is the polish stage that is causing the problems. I personally polish with a thickened sugar like syrup. Lots of people have problems doing the sugar. captbob's suggestion about using plastic pellets sounds like the way. or some form of padding.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 14:55:52 GMT -5
Well, maybe the stones can't be polished anymore? Is there such a thing as too much aluminum polish? Perhaps. I re-tumbled a certain batch of jaspers and agates and they didn't seem any better than before. Any stone will polish up to a point and then stop getting better. I recently ran some Australian pink opal and it polished out to a point and stopped. Under a magnifying glass the surface had a texture not unlike human skin, but to the naked eye they were acceptably glossy. This is not what's happening here. These were nice right up to the end of the 500 stage with NO damage. They were high gloss when wet and showed no damage when dry. In the final stage these never reached much of any polish on most, while some polished out okay with no damage. Those few I am re-polishing in a 3 pound barrel. The others look like I just picked them off of the street after they ricochetted out from under a truck tire. It's something weird that happens ONLY in the polishing stage.
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Post by adam on Aug 13, 2015 15:05:52 GMT -5
Not enough water? Not enough cushioning? The suspense is killing me. Is it the media?
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 15:29:56 GMT -5
Not enough water? Not enough cushioning? The suspense is killing me. Is it the media? LOL ... that's why I'm asking all of you out there. I don't know. Read the first post details for water level, media, and everything else. Like I said, my formula works perfectly, then it doesn't ... and it can be on the same type of stones that previously worked perfectly without any change to the formula.
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Post by glennz01 on Aug 13, 2015 17:04:58 GMT -5
I get that when the stones are softer than the other stones (I throw everything in together mostly ) it does this the most with feldspar for me
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,711
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Post by Fossilman on Aug 13, 2015 17:26:39 GMT -5
I am new at this tumbling game too-I never use filler of any kind,just slurry and different stages of grits.... I wash through every load,even the equipment.... I tumble for two weeks or more on most stages of tumble too,but that's my perference ....... Hope you find the problem and continue on with the world of great tumbling.......
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Post by adam on Aug 13, 2015 18:00:54 GMT -5
Hey, does the amethyst and quartz come out in worse quality than the jasper? Polish always finds its way into crevices in quartz, but jasper is very ceramic-like after final polish and the media is less likely to stick to jaspers/agates. Maybe tumble the quartz and sunstones together separate from the jaspers/agates? See if that improves the final polish? I'm sorry if that sounds backwards. Is it possible for quartz and chalcedony to not have the exact same hardness of 7?
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 13, 2015 18:45:49 GMT -5
Hey, does the amethyst and quartz come out in worse quality than the jasper? Polish always finds its way into crevices in quartz, but jasper is very ceramic-like after final polish and the media is less likely to stick to jaspers/agates. Maybe tumble the quartz and sunstones together separate from the jaspers/agates? See if that improves the final polish? I'm sorry if that sounds backwards. Is it possible for quartz and chalcedony to not have the exact same hardness of 7? I haven't tried a lot of amethyst or clear quartz yet. There were a few pieces in this "suicide batch" and they didn't do well. I have done yellow aventurine, jasper, blue apatite, opal and a lot of glass with great results. Not so good is calcite (too soft). Difficult is indigo gabbro. Impossible is hickoryite. It's possible for stones with the same hardness to act much differently. Apatite is a 5 and so is glass and obsidian, but apatite will wear away to nothing in a heartbeat, yet it acts like a 7 in finer grits and develops a great gloss. Sunstone is a 7 like other quartz, but it acts like a very porous stone and wears much faster than other 7's. Indigo is a 5 like obsidian but it's a composite stone so parts of it are harder than other parts so it's very difficult to get it to grind evenly across a surface. I think it does better with hand grinding and polishing. I'm doing this for commercial purposes so I have to work out formulas that work consistently every time, then pick the stones I can do well and stick to those.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,547
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Post by tkvancil on Aug 14, 2015 10:41:48 GMT -5
The green stone looks to be aventurine. Often has mica flakes in it I believe. The blue rocks look to be blue quartz. I have had both of those go wrong on me in the polish stage. They look and feel smooth out of previous stages but develop what I call micro pits. My opinion is that the slurries in the first stages prevent this. The polish slurry is thin enough to allow rock to rock contact knocking loose those softer or looser parts of the rock.
I have also experienced something similar in post polish burnish. I use borax for the burnish. Nice looking polished piece is all pitted after the borax burnish. When it happens it always seems to be with quartz family rocks. The 1/4 cup of borax you are using seems like a lot to me. I have had a slurry go too thick on me in my QT66 with only 1 tablespoon added borax. I do however use less water than you. I no longer add borax to any stage except burnish.
It sounds to me that you may be a little under loaded and a little over watered. I fill my 66 to about 3/4 or so below the rim. Roughly 4 & 3/4 to 5 & 1/4 pounds. I use 3/4 to 1 cup water which isn't visible without tilting the barrel. When I used to polish in a 3# rotary I always filled to 80 to 85% with rock and or ceramic only. I also used 6 tbs. polish, Lortones suggested amount, with 5/8 cup water and no thickener. I arrived at this formula over time and got better results than my earlier efforts. Some rocks still went bad on occasion but only a few and the rest came out fine.
Hope this provides some food for thought.
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peachfront
fully equipped rock polisher
Stones have begun to speak, because an ear is there to hear them.
Member since August 2010
Posts: 1,745
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Post by peachfront on Aug 14, 2015 12:08:41 GMT -5
I've had this issue with blue aventurine not my green aventurine, amethyst, or quartz. So I dunno...at the moment I'm handling it by not polishing any more blue aventurine. My green actually takes a great polish. I might gather my remaining blue av. rough together and sell it to somebody else. That isn't solving our problem, though. It's just passing it on to somebody else...
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Aug 14, 2015 13:03:09 GMT -5
I've had this issue with blue aventurine not my green aventurine, amethyst, or quartz. So I dunno...at the moment I'm handling it by not polishing any more blue aventurine. My green actually takes a great polish. I might gather my remaining blue av. rough together and sell it to somebody else. That isn't solving our problem, though. It's just passing it on to somebody else... LOL ... I have a list now of banned stone types for the same reason; hickoryite, any calcite, anything softer than Mohs 5, etc. I've had good luck with yellow aventurine but haven't tried the other aventurines except for rogue pieces which did okay. For the purposes of this thread, I am thinking I may have to amend my formula to use only plastic media in the polish stage and in some cases split the batch in half and polish each half separately with less water to thicken the slurry and more fill level to decrease tumbling action. What I REALLY want is a variac voltage dimmer (variable output) so I can dial down the rotational RPM on the polish stage. Both the QT66 and CE machines have always seemed too fast to me and slowing it down by at least a third should lessen stone action during the sensitive polish stage. Maybe I can make one using a wall dimmer suitable for a ceiling fan.
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