Apr 14, 2005, 12:19 AM
Post #1 of 1
This is one of the more difficult things to do. Soft materials pose a problem in several aspects.
Tumbling softer materials.
First, they wear down faster, and if mixed in with harder materials in a grind, can wear down even faster.
Second, they don't polish as fast or as easily, and a number of "tricks" have to be used to get them to take a shine.
The fact that there are so many different variations and modifications of techniques is an indication that no one technique or "forumua" will work for everyone, all the time, or in all tumblers.
Also, because of the differences between rotating and vibrating tumblers, the techniques that work for one will almost certainly *not* work for the other. Rolling/rotating tumblers have significantly more impact than vibrating tumblers, which have a higher burnishing action. Yet, the shear number of micro impacts of the vibrating tumbler can add up, especially for materials like glass. If the load is too light, these micro impacts can cause flawed or internally fractured crystals and stones to break, usually in the later grinds.
Softening the impact with plastic pellets works ok in a rolling tumbler, but seems to have the opposite effect in a vibrating one. Using plastic pellets in a vibrating tumlber's polish cycle seems to prevent polishing of many materials -- possibly due to the drastic interference with stone-to-stone contact. The use of corn syrup or sugar to increase viscosity also works, as does adding extra liquid to the vibrating tumbler to slow the motion down.
Polishing is more of an "art" than a science.