Best New Tumbling Product in Past 30 Years
People ask me what has changed in the world of rock tumbling over the past 30 years. They remind me that we have had both rotary and vibratory units during that period, that the Silicon Carbide grits have remained the same, and the polishing powders are pretty much the same. So what has changed in our little world of rock tumbling since 1970?
My answer is the increasing use of ceramic shape mixtures (CSMs). CSMs are now being stocked by enlightened lapidary houses and used successfully by tumbling operators everywhere. They usually consist of several sizes of “angled cylinders”, some spheres and sometimes one or two other shapes--these are made out of very hard materials with a relatively low Specific Gravity, like Aluminum Oxide and Porcelain.
You put the CSMs into the rotary or vibratory tumbler at any stage in order to (a) cushion the tumbling action, (b) to make up for lost volume, or (c) to act as a “carrier” for the slurry. The CSMs roll and vibrate right along with the rocks, and since they are too hard to embed with the sharp Silicon Carbide particles, you can wash the CSMs with the rocks and let them go right along into the next stage of tumbling without fear of contamination. These mixtures of ceramic shapes are expensive to purchase--about $45.00 for 6 pounds--but they last for many, many batches. Considering the amount of improvement in the shape and finished quality of the rocks, the ceramic shapes are definitely cost effective.
The CSMs should be run in 80-grit SiC for 1-2 days to remove the sharp factory edges, which may scratch a polish batch or a batch of soft obsidian. After this “Break-In” period, they can be safely used in any stage with any batch.
CSMs replace the rubber bands, sawdust, bits of plastic, poly pellets, leather strips, molasses, honey, oatmeal, and many other “favorite” media we have used in the past to alter the internal environment of the barrels, mainly to reduce the force of rock-to-rock collisions. Today, you can toss them all out and use just this single “magic media”.
Let’s cover how the CSMs are used. First, in batches of soft material like obsidian and apache tears (Mohs-4), I advise that you start out Stage 1 with a 50-50 mix of rocks and CSMs. As Stage 1 wears down the rocks and creates rock powder, volume is lost. You need to make up this lost volume with more CSMs. I keep a homemade template on hand to measure the batch volume so I start out each new week with the barrel 75% full. This consistency of barrel volume allows me to measure out the same volume of water for each barrel, which in turn causes the resulting slurries to be very consistent in their viscosity (thickness). Consistently perfect slurries mean that the cutting or polishing action will be very efficient as you work through the Stages of a batch.
If I am tumbling agates, which are quite hard (Mohs-7), I generally won’t add the CSMs in week one, but use them primarily for volume makeup.
30 years ago, the rock tumbling literature was full of formulas for achieving a “balanced load”, where the rocks had a smooth size distribution from small to large. Distribution of sizes is important to insure that the slurry is deposited in all the “nooks and crannies” for even size reduction and finishing. Today we can put just one rock in a tumbler, add a pound or two of CSMs, and the slurry will be carried evenly to every part of the rock. This is especially important when we have 1 or more preformed shapes (crosses, cabochons, etc.) we want to process. CSMs allow us to vary the volume while keeping our quality high. This is a huge benefit for the custom jewelry maker who assembles one or two pieces at a time.
Volume replacement is less important in vibratory tumblers, because we establish the perfect thicker-than-average viscosity visually, as we make very small adjustments in water and powder, until the slurry is clinging to the rocks as they follow their toroidal path around the bowl.
These are just a few of my reasons for nominating Ceramic Shape Mixtures as the most significant rock tumbling product improvement over the past 30 years. It’s probably time for you to purchase some and start reaping the advantages they bring to the rock tumbling process.
Little Red Store has been selling CSMs since it opened in August of 2008. We also supply other lapidary dealers who want a high quality product to offer their customers. If your dealer is not carrying CSMs, send them to us and we will be happy to supply their needs.