Science Gifts Unwrapped: the Rock Tumbler

I haven't done much with a rock tumbler since I was a child, when one of my father's brief enthusiams led him to play with one and to try and interest me in it as well. For whatever reason, I wasn't patient enough to be interested as a child, but, having worked around them and explained them to people for a year and a half, now, I found myself wanting to try one out for myself.

Strangely enough, therefore, one appeared under the tree for me this year, and once the haze of new gifts had worn off, I found myself eager to set the tumbler up and get it going. A little more than a week later, here's what I have to report.

The tumbler that I received, the Lortone Model #33B (Beagle Webstore | Lortone site), features two three pound capacity rubber drums, which are rotated on a direct-drive chassis. The practical result of this is that you can either double your tumbling capacity over the Model #3A, or you can have two batches at two differing stages of polish running at the same time. Not clear yet? Don't worry, it will be.

Set up is a breeze with a tumbler, but it pays to have thought out your tumbling process, just a bit. First thing out of the box, you'll want to have some oil for the bearings on your tumbler. Lortone recommends oiling the bearings (the four points where the spindles intersect with the tumbler housing) before you start, and then once for every thirty days of operation afterwards.

You'll also want to have a space which is sufficiently remote from the rest of your home that the noise won't be distracting. The rubber-barrel direct-drive tumbler is quiet, but it's still audible enough that it won't be something you'll want in your bedroom. Laundry rooms, basements, or garages are the typical sites. Make sure that you have a level surface, like a workbench or table, with easy access to electricity. You'll also want ready access to water. I don't have any taps in the basement, so until I can come up with a better idea that doesn't involve my having to attempt anything resembling plumbing, I've got a number of buckets - for clean water, and rinse water. And remember - although I'm going to say it again later - NEVER put the water / slurry / waste from your tumbled barrels down your home plumbing. EVER. Why? The slurry, when poured out, tends to solidify into something with roughly the consistency of concrete, particularly at bends in the piping. Find another place to pour it out: it's that simple.

While I'm on the subject of slurry, I've heard it claimed that it's possible to reclaim at least some of the grit for re-use after tumbling. I'll have to report back on this, but at the moment, I'm somewhat at a loss to see exactly how that might be done. Perhaps washing it and then pouring the debris off through filter paper? If you've done this, drop your suggestions in the comments, otherwise I'll re-post when I've tried it.

But back to the subject. Now that you've prepared a work area, and oiled your tumbler, it's time to fill the barrel(s) and get weaving. There are plenty of sites out there, as well as books, that cover this. I'd just add that you need to be absolutely certain that your barrel is sealed. If it isn't, and it starts leaking, things can get very messy very quickly, and your batch won't be properly tumbled.

Choose your rough with care, but feel free to experiment. There's no wrong way to tumble rocks and minerals, and the only way to learn what works in each situation is to make a few mistakes. I started with one of the Beagle's batches of high quality tumbling rough, which is turning out to be a great mix of amazonite, tiger's eye, carnelian, chrysoprase, unakite, rose quartz, amethyst, and others, but you can start wherever you like, with whatever you like. I added the rough to the tumbler, then added the coarse silicon carbide grit and water to the appropriate level. Think of grits like sandpapers - beginning coarse, and then increasingly fine. Then start the tumbler.

Rock tumbling takes time. But you knew that already, right? The first cycle, depending on the hardness of the materials, can take between five and ten days. You should really check every day or two, to make certain that you have no leaks, and that you do not have any build-up of pressure in the barrel. Dip out a stone or two just to see how things are going - even after a few days, you should start to see smoothing of the rougher edges. After seven days, I removed the rough in my first barrel, rinsed it, emptied out the slurry, rinsed and dried the barrel, then recharged the barrel and added the next finer round of silicon carbide grit. The rough was already significantly smoothed and shaped. Filled with water, the process continues, with a second new barrel, beginning again with the coarsest grit, this time with a batch of rough corundum, agate, and hessonite garnet.

That's the process so far. Repeat according to directions, and watch your rough turn into attractive, decorative, and interesting tumbled stones. It's easy, if time-consuming, but the results will delight both you and your friends. So try out your new tumbler, and see what treasures you can produce!

There are sites out there to help you, too, as well as books. Rock Tumbling Hobby, and Rock Tumblers for example, both provide some excellent tips and good information. One other thing that they will mention which I must also say again: NEVER put your slurry down your household pipes. Not in the kitchen, the bathroom, the lavatory or directly into the mains drain. Find a place outside instead, preferrably somewhere that you can observe the accumulation over time, to see why this is such an important point. I'll be watching mine with interest (after things thaw, that is).

Happy tumbling!