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Daily Wire Tip: Rock Tumbling 101

By on October 11, 2010
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Daily Wire Jewelry Making Tip

Question:

I recently bought some small slabs for wiring at a lapidary show that just need some shine put on them. I have a tumbler that I have never used. What do I put in it? Or do I need to polish them some other way?

-Phylliss in Searcy, Arkansas

Answer:

Although I enjoy lapidary questions, to give a complete answer to your question I would need a bit more information such as:

  1. What style of tumbler do you have, rotary or vibratory?
  2. How large are the slabs? (Big ones should go into a vibratory tumbler; small ones can be done in a rotary)
  3. What are the materials? (Rocks need to be separated by hardness to tumble polish, as softer materials can be quickly ground away or beat up by harder materials)

After you have determined the above answers, you will need some grit (generally silicon carbide, a minimum of 3 grades from coarse to fine, depending on the hardness and material type), a polishing agent (again, this will depend on the materials you are tumble polishing, usually cerium oxide works well on most materials) and a separating medium (I like plastic pellets) to keep the slabs from sticking together for a nice even finish.

To tumble wet (usually in a rotary tumbler), you would place the slabs and plastic pellets into the tumbler’s rubber barrel and add enough water to fill it 4/5 of the way, then add the grit (coarse first; the amount depends on the size of the barrel). Tighten the lid and turn it on for the first run. The amount of time required for each run will depend on the hardness of the stones, from a couple of days to weeks. When the first run is complete, empty the barrel (never into a sink, as the slurry can really mess up plumbing systems), and thoroughly rinse and clean the pellets and the stones. Then repeat the runs, using medium grit next, and finally the fine. When you are happy with the results, it is time for the polish.

Be absolutely, positively sure that there is no grit whatsoever left in the barrel or on any of the stones, as one piece could destroy weeks of work! I have barrels just for polish. The polishing run can take less than a day, again depending on the stones. Wash your stones completely, and wrap as desired!

In a vibratory tumbler, I prefer to tumble slabs dry, using the same processes as above without adding any water, as I find slabs tumble polish more quickly in a vibratory tumbler, dry. For an easier solution, you could use a spray protectant, like as an acrylic spray such as Krylon, to give your slabs a nice glossy finish; just be careful not to scratch it when wrapping.

For lapidary supplies such as grit and polish, simple do an Internet search using the phrase “tumbling grit.” Warning: Polishing your own stones can be addicting!

Answer contributed by Dale “Cougar” Armstrong

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14 Comments

  1. avatar

    Jane Elizabeth

    October 12, 2010 at 7:45 am

    Dale,
    I love the information about polishing stones… in my deepest dreams of the “perfect profession and hobby” I would list the desire to do lapidary work. I can only imagine how infinitely rewarding and addicting this work must be. Facinating how labor intensive the work is and yet how profound the result. Taking God’s creation from “raw” to “finish” in the steps you have explained! Bravo!

    • avatar

      dalecgr

      October 12, 2010 at 9:23 am

      Thanks Jane – this is just a very basic set of directions. Tumble polishing can take a long time but is so rewarding : )

  2. avatar

    Carolynne

    October 12, 2010 at 9:11 pm

    Which if purchasing only one would you recommend – rotary or vibratory? Wirewrap ond pmc and simple soldering…

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  4. avatar

    Brent

    December 9, 2010 at 11:25 am

    I have been tumbling stones for several years now, and one of the easiest ways that I know of is as follows.

    -fill the barrel about 1/2 full of rocks with the same hardness, in other words don’t put agates in with opals.

    -add water to just cover the rock (if you fill more than 1/2, the rocks wont have room to tumble)

    -add 60/90 diamond grit
    -add a couple of drops of dish soap
    -let run for 5-6 weeks (the diamond will break down and become the 400, 600, and 1200 grit)

    -rinse stones and barrel thoroughly, add final polish (cerium, tin-oxide, fiber optic, etc….) and run for another 3-4 weeks.

    This method takes longer, but is fool proof, and does not run the extra expense of diamond grits.

    • avatar

      dalecgr

      December 9, 2010 at 6:22 pm

      Humm Brent – I’ll have to try this method on some agates. Thanks for sharing!

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  6. avatar

    Ken Kress

    March 13, 2012 at 11:45 am

    Once the first step is complete and you clean everything put the stones back in the tumbler with warm water and 2 or 3 drop of dish soap (original plain Dawn) and run for 24 hours. You will be surprised how much grit and dirt you will get out. Wash everything again and go on to the next grit.

  7. avatar

    charlotte

    March 16, 2012 at 5:18 am

    i tumbled a few stones a few times but i never get the shine i get buying pre-tumbled stones and i have no idea why,,i have tried three or four times,,once i tumbled them so long that i shrunk them to almost nothing,,but still not the shine i want,,so,,i quit trying even though i have about a pound and a half of stones waiting to be done,,im tempted to try simonize paste wax and my moto tool to and polish them,,,hey it works on my kitchen floor,,

    • avatar

      dalecgr

      March 16, 2012 at 6:13 am

      Hi Charlotte, properly tumble polishing stones just takes a little research. Be sure to separate them by hardness before tumbling different stones together; between stages, make sure all of the previous grit has been removed/washed off; use the correct polish for the right amount of time.

  8. avatar

    Sheri Clark

    July 31, 2012 at 1:08 pm

    The best finish on tumbled stones I’ve ever gotten was done by using a rotary polisher for the first 3 stages then shifting to a vibratory for the final polish. For slabs,use an angle grinder turned upside down. Much easier.

  9. avatar

    Bill

    February 5, 2013 at 5:26 pm

    When you finish tumbling your stones always cut up about a half bar of Ivory soap and run the stones for about 2 or 3 days. I always put cut up rubber bands in there to keep the stones from breaking as well as in the polishing stage. This is the only way I can get a very good shine on my rocks. Hope this helps.

  10. avatar

    athan

    June 20, 2014 at 10:41 am

    has anyone tried to use a magnetic tumbler with stones?What will happen?