When tumbling rocks, it is common to use some sort of cushioning material in the polishing stages. This reduces frosting on the edges and may prevent chipping.
A variety of materials can be used for this cushioning. We will focus on three of these in this investigation: Beads, Plops and Rubber Bands.
Beads are small bits of a tough plastic very similar to weed whacker cord. They float in water and as they are convex, they do not stick to surfaces. You can easily seperate beads from the rocks by flooding with water and scooping them off.
Plops are bits of plastic that are somewhat softer than beads and that have a convex and a concave side (manufactured by plopping the material). Because of the concave surface, the plops stick to flat and slightly curved surfaces. This is a hassle during cleanup as though they float in water, you will spend significant time getting 100s of them off the inside of your tumbler barrel. However, because they cling, it might be that a little bit of polish gets into the concave pocket and then rubs on the rocks. Plops might be better than beads in polishing performance.
Rubber bands are another cushioning option. They float in water. They don't have a concave surface and their stranded structure may work even better than the plops concave face in rubbing the polish across the rocks. They might even cause extra tumbling in the drum by cross-linking stones and providing an additional source of rotation.
In this investigation, we will compare beads, plops and rubber bands to see which works best in producing well shined rocks (surface that is unchanged wet or dry), in the least time, with the least hassle.
8 Ounce Sample of Each Material (Click Photo To Enlarge)
Close Up View of Each Material (Click Photo To Enlarge)
It is clear, of the three materials considered, plastic beads are the best cushioning material that one can use in a rotary rock tumbler. I had hoped for some definitive photos, but the product one gets in using the three is indestinguishable. The difference is in the amount of hassle that comes with using each different cushioning material.
The beads worked great - every time. Just pour them in. When it is time to clean the mud from the rocks, add a little water and the beads float right to the top. Ladle them off with a screened ladle and and rinse them with water and they are ready for the next batch and your rocks are clean. Beads do not stick to your hands or the drum wall or the rocks. They are effective, simple and easy to use.
The plops produced a shine that looked like that done with beads. However, the plops were a real pain when it was time to clean the mud from the rocks. Yes, plops float - but a significant number of them always stick to the inside of the drum - and I mean really stick. Even with lots of water, plops stick to your hands and to the rocks as you try to handle them. I have quit using plops as they are just not worth the hassle.
Rubber bands were interesting. I got signifcant wadding of the bands and found that they didn't actually float in water as I had thought. Chalk this one up as a good college try but I wouldn't use or recommend that anyone else use rubber bands. But if you are really eager to try them, I suggest chopping them into short segments so they have little chance to wad up.
Bottom line - use beads - specifically, Thumler Tumbling beads.