Burnishing Tumbled Stones or Glass in a Rock Tumbler
What is Burnishing?Most stones or glass that have been processed in a rock tumbler look pretty good at the end of the polishing step. However, there is one more short step that might significantly improve their luster and really make them shine. That step is known as "burnishing". It involves running the stones in a heavy soap bath for a couple of hours.
The Buffing TestTo determine if burnishing will improve the luster of your polished stones or tumbled glass or whatever you have tumbled you can perform the "buffing test". That involves rubbing one of the stones very rapidly on a soft piece of cloth. You can easily do that by rubbing it on the sleeve of a flannel shirt or a t-shirt or a pair if jeans.
Pick a nice flat surface on one of your stones and study it for a moment to become familiar with its luster. Then rub it very rapidly on the soft cloth for fifteen to twenty seconds - enough time to build up a little heat. Then examine the flat surface to see if the luster improved. If it improved then a short burnishing should improve the luster of the rocks.
Preparing to BurnishPlace your polished stones in a perfectly clean tumbler barrel. Be sure that the barrel is 1/2 to 2/3 full. Add ceramic cylinders if you don't have enough material to fill the barrel or if you need small particles as cushioning between large rocks. If you are using ceramic media be sure that it has been tumbled before. Brand new media often has some sharp edges that can scratch up your rocks. We usually add some plastic pellets to cushion the rocks while they are being burnished.
Burnishing SoapWe use Ivory bar soap that has been cut into small pieces. We cut a few slices with a sharp knife and add about 1 tablespoon of chopped soap per pound of rock. Some people use a powdered laundry detergent for burnishing. Tide and Ivory Snow powdered detergents are reported to work well - about one teaspoon per pound of rocks.
The Burnishing StepYou don't have to run the burnishing step for a whole week. A few hours or overnight should be long enough. Then open the tumbler and clean up your rocks. Wow! They should look great!
More Information About TumblingFor more information about rock tumbling check out our detailed rock tumbling instructions, our rock tumbler resource page or Steve Hart's book titled "Modern Rock Tumbling".