Rock Tumblers » Rock Tumbler Media
Rock Tumbling Media
Plastic pellets or ceramic beads added as filler or cushioning.
What is Tumbling Media?
The words "tumbling media" sound like news reporters assigned to write stories about people who like to tumble, the exotic rock materials that they work or the colorful gemstones that they produce. Tumbling media is not quite that exciting but it can be very important to your tumbling success.
Tumbling media is a non-rock material placed into the barrel of your tumbler to cushion the rocks from impact or to serve as a filler. The plastic pellets and ceramic beads shown in the photo at right are examples of rock tumbling media.
Small pellets made from soft plastic work nicely to cushion the rocks as they bang into each other while being tossed about in the tumbler barrel. Plastic pellets are most often used in the prepolish and polish steps for cushioning and in the earlier steps if necessary to bring the volume of the barrel up to 2/3 full.
While tumbling, the pellets also help deliver the grit or polishing agents to all surfaces of the rocks (if you tumble large rocks of a single size together there will be very few points of contact between the rocks. Adding small rocks, plastic pellets or other media will fill the space between the rocks and deliver grit to all rock surfaces.
It is helpful to note that although the plastic pellets can be reused, they should not be reused with finer abrasives. For example: pellets used in the fine grind will have particles of fine grit in them, and will scratch the rocks if used in the pre-polish step.
Some of the plastic pellets used for tumbling will float. This allows you to easily separate them from rock and spent grit after a session of tumbling. Gently dump the contents of the tumbler barrel into a plastic bucket or basin of water and skim the pellets off of the top. If you want to reuse the pellets later you can let them dry and store them in containers or zip-lock bags labeled with the size of grit that they were used for.
Ceramic beads are another popular tumbling media. They are mainly used as a filler to bring tumbler barrels up to operating capacity. For example: tumbling barrels produce the best results if they are run between 2/3 and 3/4 full. If you have less rock than this optimum load, tumbling media such as ceramic beads can be used to bring the load up to optimum size.
As with plastic pellets, small ceramic beads will help deliver the grit and polishing agents to all surfaces of the rocks and limit the severity of rock-to-rock impacts that occur in the barrel.
This addition is also useful when large rocks of similar size are being tumbled. The small-size media fills the voids between the rocks. This reduces the impact between rocks but increases the amount of friction and delivery of grit to the rock surfaces.
Ceramic beads have an advantage over plastic pellets - abrasives do not become embedded within them and rinse off easily. This simplifies clean-up between tumbling steps. When you are finished with the fine grit step, simply rinse the rock and ceramic beads together and load them into the next barrel for pre-polish.
Now you are ready for Rock Tumbling Instructions
|This photo shows three examples of tumbling media. Pictured from top to bottom are: plastic pellets, small ceramic beads, large ceramic beads. Plastic pellets are used to cushion the rocks from impact during the polishing steps and ceramic beads are most often used as a filler to bring the load of a tumbler up to the recommended operating capacity of the barrel.
View of a three-pound tumbler barrel just opened after running aluminum oxide polish with rocks and plastic pellets for several days..