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Daily Wire Tip: Rock Tumbling 101
Daily Wire Jewelry Making Tip
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
Although I enjoy lapidary questions, to give a complete answer to your question I would need a bit more information such as:
- What style of tumbler do you have, rotary or vibratory?
- How large are the slabs? (Big ones should go into a vibratory tumbler; small ones can be done in a rotary)
- 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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