What to Know about Rock Polishing
If you’ve ever been to the beach, you’ve probably picked up rocks that are perfectly smooth and rounded. The ocean is a natural rock tumbler: as rocks are rolled by the waves and rubbed against sand and each other, their rough edges and corners are filed away. Learn how to polish rocks like the ocean!
A rock tumbler can mimic this process and even take it a step further by adding polish to make the stones shine. Rock tumblers work much faster (4-6 weeks) than the rock cycle steps of the ocean because their motion is constant. They also use an abrasive substance called silicon carbide, which is much harder than sand.
Lapidary is the art of cutting and polishing gemstones. Rocks and minerals come in all different colors and patterns, and polishing them to a smooth shininess brings out their incredible beauty. Polished rocks are often used in jewelry.
Rock polishing has several stages to achieve a nice looking polished rock. It normally takes 5 stages and a few burnishings (washing in the tumbler barrel) to do it. Specific instructions.There are 2 types of rock polishers: rotary and vibrating.
As the name suggests, a rotary tumbler slowly rotates causing the rocks inside a watertight barrel to slosh back and forth in a grit and polish slurry. This results in the slow smoothing and polishing of the rocks.
A rotary tumbler will use a lot of grit and polish. The rule of thumb is about 1-lb of grit for every 10-lbs of rocks. So if you had a 4-lb rotary tumbler you would use about 0.4-lb of grit per barrel load of rocks. A rotary will shape the rocks MUCH better then a vibe but takes months to do a full cycle from the rough rocks to a finished polished load.
The rough stage will use the most grit as it takes the longest to round off the rocks and get rid of any imperfections in them. The rough stage is about the most important as it will decide the final result you have. The rough cycle can take several months to do properly. This means that every 7-10 days you will have to empty the barrel, wash the rocks and barrel and start over again until you are satisfied with the way the rocks look. The 2nd, 3rd, 4th and 5th stages usually take 7-10 days each in a rotary polisher, plus the burnishings.
A vibrating polisher (vibe) works in a similar manner to the rotating one, except instead of rotating, the polisher simply vibrates as a high rate of speed. The action of the grit and polish slurry on the rocks cause them to be polished.
A vibe will polish rocks much faster (7-10 days) than a rotary polisher, but the rocks will not be nicely rounded. The vibe is very economical as far as grit and polish goes. With a 4-lb barrel you would only use about 2 to 3- tablespoons of grit for every 4-lbs of rocks for the roughing stages. Vibes are MUCH more aggressive, so you will have to re-charge the barrel every 24 hrs. The 2nd, 3rd, 4th and 5th stages in a vibe will only use 2 tablespoons of grit in the 2nd stage and 1/2-teaspoon each for the 3rd, 4th stage and 5th stages!