incult
off to a rocking start
Member since October 2010
Posts: 24
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Post by incult on Oct 25, 2010 21:41:20 GMT -5
I'm new to rock polishing and by now I mostly polished beach pebbles. I was wondering if anyone has some formula to polish the softer rocks, the ones that scratch with a pocket knife.
Thank you!
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Post by Hard Rock Cafe on Oct 25, 2010 21:50:00 GMT -5
I don't polish soft stuff myself, except by accident. What I have learned is that if you mix hard and soft, only the hard rocks will polish.
Chuck
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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 1:41:39 GMT -5
This can be a tough gig, frankly because not all soft rocks will take a polish. Once you get below about 6.5 MOHs, it can really be hit or miss. It's not entirely the hardness that counts, but rather the types of rock that really matters. One of the tricks is to make sure you're working with all the same rocks and it's also usually best to leverage a fair amount of cushioning. (Like over 50% ceramics/pellets) Also, a lot of the time, your average CO or AO isn't going to coax a polish...you sometimes have to get into some of the more obscure polishes like tin oxide, chrome oxide and high grade aluminum. Consult this table for some recommendations. www.utahrockhounds.com/tooelegem/tips/stonepolish.htmlI've personally only worked with a couple soft materials. I tried Flourite, which is in plentiful supply around here and is known to take a polish, but it was a pain to say the least. I won't even bother working with the material again because it was such a pain...but I was finally able to get a reasonable haze, though nothing like your harder rocks. Wonderstone was a similar experience for me, which is really too bad because I've got a fair amount from a slag pile I dug through and it would look awesome with a good polish. Personally, I take my softer rocks that are worth keeping and run them through a short stage of rough until they're smooth/rounded. I then use them in pots with various high desert succulents I've found around these parts. Don't mean to discourage you - and others may have some good advice - but I do wish you well and it's a fun challenge when you've mastered harder rocks and mixed loads. 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 9:01:26 GMT -5
Had a nice piece of common opal, solid and easy to shape, but couldn't get better than a smooth haze finish. I tried all kinds of polishes, and finally tried cheap white toothpaste, it worked great. This was a hand polish project not a tumble, but it might work. Use plenty of cushioning mtl.
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Post by susand24224 on Oct 29, 2010 1:47:58 GMT -5
I've tumbled quite a bit of softer materials, with fairly good results. It really isn't that different from harder materials, although some of it won't polish.
If it's really soft, skip the 60/90 stage and go straight to 120/220.
Add something to the water to thicken it; I used to add borax, but recently had a problem with it "dulling" fluorite. I tried again with fluorite and Ivory Soap shavings, and it worked well.
Check each new grit stage after three days rather than the usual week or so--softer materials wear down very quickly.
If your material is both soft and brittle (turquoise and fluorite are examples) fill your barrel a little more than 2/3rds--this also lessens the "impact" of the stones.
I add 1/3rd to 1/2 volume ceramic shapes. I rarely use plastic pellets, but others do with success.
Always add a 1000 grit stage.
AO polish from the Rockshed has always worked well for me but it often takes several weeks.
Susan
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Post by johnjsgems on Oct 29, 2010 8:04:36 GMT -5
I would try Susan's methods but spring for finer aluminum oxide (.5 or .3 micron). Tripoli will work instead of 1000 alumina prepolish also. You might want to try a mix of submicron aluminum oxide and chrome oxide.
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gstan30117
off to a rocking start
Member since March 2011
Posts: 4
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Post by gstan30117 on Jul 16, 2011 1:29:59 GMT -5
I've tumbled quite a bit of softer materials, with fairly good results. It really isn't that different from harder materials, although some of it won't polish. If it's really soft, skip the 60/90 stage and go straight to 120/220. Add something to the water to thicken it; I used to add borax, but recently had a problem with it "dulling" fluorite. I tried again with fluorite and Ivory Soap shavings, and it worked well. Check each new grit stage after three days rather than the usual week or so--softer materials wear down very quickly. If your material is both soft and brittle (turquoise and fluorite are examples) fill your barrel a little more than 2/3rds--this also lessens the "impact" of the stones. I add 1/3rd to 1/2 volume ceramic shapes. I rarely use plastic pellets, but others do with success. Always add a 1000 grit stage. AO polish from the Rockshed has always worked well for me but it often takes several weeks. Susan When I get to the polish stage from here I switch to my TV-5 and add enough corn cob to fill it up. Add 3 teaspoons of AO polish and a handful of stones and let it go. Remember, this is a dry polish. About two days should do it. Should give you an nice shine on Fluorite, Apatite and Apache Tears. Calcite Will shine but still look scuff over the shine. I'm going to try it alone next time and use TO in the corn cob. I've started using corn starch to thicken the wet stages, work extremely well but start of slow and see how it works., might take more water. Good luck
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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 Jul 16, 2011 12:36:42 GMT -5
Revco, I don't know how to tumble polish Rhyolite Wonderstone but I have got a polish on it by working individual pieces on diamond cabbing wheels. I have 3000p and 8000p wheels, and they seem to work OK.
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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 Jul 18, 2011 19:50:00 GMT -5
I hate polishing soft stuff but do occasionaly do it and I prefer a high grade tin oxide for the polish with soft materials. I don't mix types in these loads if I can avoid it and I used lots of plastic pellets in every stage except coarse. I only do the last three stages for soft materials in a vibe tumbler as rotaries can be a bit rough...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 Jul 19, 2011 8:05:12 GMT -5
I have nothing to add except some reinforcement of others ideas.
I use a 1000AO for softer materials(actually I use it for almost everything except the hardest PW and Agatees)
I would try Tin Oxide for polish
Anything that tends to frost, like beach pebbles, seem to defrost with extra cushioning. I use plastic pellets; others here sear by ceramic.
If you do use plastic they are reuseable but segregate the pellets for each grit stage or they may carry contaminants.
Charlie
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stonemaster499
noticing nice landscape pebbles
Member since July 2014
Posts: 97
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Post by stonemaster499 on Sept 27, 2014 19:14:54 GMT -5
I agree with gstan30117: FOR SOFT STONES: use DRY POLISH method with CORN COB media - which is listed on RS site "how to polish fluorite or soft stones". www.therockshed.com/instructions3.htmlI get a high lustre polish on labradorite and apatite so far using this method. I'm shocked there is so little info on this site for softer stones!! I'm even more floored by those that inform others it cannot be done. (labradorite, apatite, fluorite, calcite...etc. Mohs 3-6) with less than impressive results. Apatite requires stabilizing, like turquoise).
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