DIY Rock Tumbler

Roan Art

Roan Art

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Oct 7, 2005
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I'm setting up 3x75g tanks with a Papua New Guinea river/lake theme. Currently I am using a 36g bowfront with about 58# of Black Pearl soapstone in it. I really like the look of the stone, but it's quarried and therefore a little jagged and there are cut sides. I want to smooth them out a bit to give them that large "river rock" look.

The soapstone is really steatite and yes, it's inert. I've tested it with hydrochlorite acid. They are about a 4-5, sometimes 6, on the MOH scale. I'm an artist and normally use these for carving. I had a few large pieces I wasn't using and threw them in the tank. I love the look :)

Some of the pieces I want to use are 30-40#. Those ones I could probably smooth by hand, although it's rather tedious :)

What I want to do is make a "temporary" rock tumbler that can hold 10-20# stones, although being able to put 30-40# stones in it would be ideal. I don't need a polish, just a smoothing of the rough edges and faces. I have no real clue how to go about this.

I was thinking of using one of those large 10 gallon white plastic paint buckets, clamps on the lids, and some sand as grit. Afix that to a spit-like device and manually turning it. Dunno if that's how it's done or not :)

Can anyone help? Offer suggestions?

Roan
 
Sounds OK, but I think sand might break down too fast. I'm thinking for your first grit, for such larger stones, if you could even get pebbles (or the very small aquarium gravel) that might work better.

I do lapidary (rock tumbling) and the first coarse grit is silicon carbide (of 60 to 90 grit size), but these are just small stones, the biggest 1 inch diameter. After 10 days that grit breaks down and becomes a sludge. Now, in a rock tumbler, it's going 24/7 for 10 days on each successive grit and then finally the polish. You'd be sitting there a long time turning the thing to get any good results. Might build up some good muscles.
 
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kveeti said:
Sounds OK, but I think sand might break down too fast. I'm thinking for your first grit, for such larger stones, if you could even get pebbles (or the very small aquarium gravel) that might work better.
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Good idea.

I do lapidary (rock tumbling) and the first coarse grit is silicon carbide (of 60 to 90 grit size), but these are just small stones, the biggest 1 inch diameter. After 10 days that grit breaks down and becomes a sludge. Now, in a rock tumbler, it's going 24/7 for 10 days on each successive grit and then finally the polish. You'd be sitting there a long time turning the thing to get any good results. Might build up some good muscles.
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I was hoping someone who did that would read this and offer some suggestions :)

Is there any way to motorize it? I was thinking of getting a pully and some belts and hooking it up to the snowblower :)

Roan
 
Ok, first I was looking up soapstone, and it is soft - a "1" on the MOHS scale. So, therefore, the sand might be all right after all.

The MOHS scale is the relative hardness of any mineral, stone, etc, which is determined by a scratch test. i.e. Silicon carbide I mentioned is a hardness of 9-1/4 a fingernail is a hardness of 2-1/2. Can you scratch the stone with your finger nail?

Edit. Oh. How a rock tumbler works for best results. You would also need a waterproof lid. The tumbler is filled 3/4 with stones. Then your grit, which should fall between the stones. Then you fill with water to the BOTTOM of the top layer of stones. So I assume the same proportions would hold true on a larger scale.

Do NOT pour any sludge that forms from the process down any plumbing, etc. You will effectively ruin it, it will harden like cement.
 
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kveeti said:
Ok, first I was looking up soapstone, and it is soft - a "1" on the MOHS scale. So, therefore, the sand might be all right after all.

The MOHS scale is the relative hardness of any mineral, stone, etc, which is determined by a scratch test. i.e. Silicon carbide I mentioned is a hardness of 9-1/4 a fingernail is a hardness of 2-1/2. Can you scratch the stone with your finger nail?
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As I said, it's more of a steatite and not real soapstone. It's about a 4 on the MOHS, some pieces are 5s.

Not all soapstone is a MOHS 1. It really depends on the locality found and mineral content. MOHS 1 is pretty much straight talc. Quarried stone varies a lot even within the same quarry. Different veins will produce harder or softer stones within the same quarry.

Most Brazilian soaps I can cut on my bandsaw. Catlinite (or pipestone) is supposed to be MOHS 2. Minnesota Catlinite can be cut on my bandsaw, but Utah and Black Ontario catlinite, remove the teeth :) The Black Pearl not only removes the teeth, but breaks the band.

So, yes, gravel would probably be best.

Edit. Oh. How a rock tumbler works for best results. You would also need a waterproof lid. The tumbler is filled 3/4 with stones. Then your grit, which should fall between the stones. Then you fill with water to the BOTTOM of the top layer of stones. So I assume the same proportions would hold true on a larger scale.
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Cool. Thank you. Now to figure out how to build it. I just ordered the stone from the quarry and it should be here next week. If I can't figure out how to tumble it, I'll just chisel a few and use some sponge sandpaper to smooth the edges.

Roan
 
Some more points. I dug out my lapidary pamphlet, and they had this to say about barrels:

quote
As barrel diameters get larger and capacity increases, it becomes necessary for the barrel walls to help the rocks "turn". This is accomplished by internal flat sides making the inside wall look 6 sided (hexagonal) on up to 10 sided (decagonal). The rotating speed of the barrel is dependent on the barrel diameter. A 4 to 4-1/2 inch barrel will rotate at 50 to 60 rpm; a 7-1/2 to 8 inch barrel should rotate at 25 to 30 rpm.
unquote

Hmmm.

There are new-fangled polishers out there that use vibrating rather than rotating. Maybe that would be something to look into, but I have no info on it, other than a new vibrating 'tumbler' was very expensive.
 
I don't have a clue about how to go about polishing stones, so please don't take this as such.

But... for a general stupid idea, how about hooking up whatever drum you intend to use, say, a barrel on it's side... you could mount it in a 3+ sided box with roller skate or skateboard trucks and wheels against it... then just drive the thing with a stationary bicycle. At least it would be good excersize. =) The noise might drive you batty though.
 
Maybe I missed it but you asked how to Motorize it.. hmms considering I remember grandfather doing rock tumbling and the days it took you would want something not too loud.. a bucket with rocks I imagine get pretty heavy and the mixture to help smooth them out as well.. wish I had idea's but the one I do is just as a silly..

Seal the washer and dryer shut and poof!.. Rock tumblers :) ..actually if you were to somehow do it as a river rock / aquarium business a motor from one of those probably not a bad idea :)
 
I've done this for an entirely different type of project (tumbling a coat of maille), but you can rent a portable motorized cement mixer from Home Depot for a day. It's not that expensive and you won't ruin your dryer.
 
Raskolnikov said:
I've done this for an entirely different type of project (tumbling a coat of maille), but you can rent a portable motorized cement mixer from Home Depot for a day. It's not that expensive and you won't ruin your dryer.
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OH, YOU ROCK!
Heh, another pun for the Roanster :)

Yah, if I tried doing something like that AGAIN with the drier . . . let's just say I already broke it once drying a buffalo hide :huh:


I'll check into that, Ras. GREAT idea!

Roan
 
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