How to Tumble Rocks

Rock tumbling is an interesting hobby that yields truly beautiful shiny stones out of ordinary looking rocks. It is a means of doing something similar to what nature does with the actions of a river or surf, in a much faster way. Let’s take a look at how we can tumble rocks.

To begin this hobby, we need to start with a rock tumbler. These are devices of two sorts; rotary tumblers and vibration tumblers. In both cases, they provide a means of using a series of abrasives to make rocks smoother.

Rotational tumblers do this by rotating one or more sealed drums containing the stones, abrasive, and water. Vibration tumblers shake the mixture rather than moving it in a rotation. Since rotary tumblers are the most common type, we will concentrate on this sort of tumbler here. However the sequence is very similar with vibration tumblers.

With some effort, these tumblers can be built, however good rock tumblers can be purchased fairly inexpensively. Single drum tumblers can be purchased, however a double drum tumbler isn’t a great deal more expensive and they allow for a succession of rocks to be tumbled so some will be at the start of the sequence while some will be nearing the finishing steps.

We also need grit for the tumbling action. This is graduated according to the coarseness of the grains, similar to the way sandpaper is graded, but it is easiest to call the different grades simply coarse, medium, fine, pre-polish, and polish. Small plastic pellets can also be purchased to keep the stones from hitting each other with enough force to chip them, however if the tumbler is properly used, these aren’t absolutely necessary.

The first step is to load the tank. This is when we put rocks in the drum until it is between half and three quarters full, add just enough water to cover the rocks, and add about two tablespoons of course grit, and then seal the drum. Avoid the temptation of overloading the tank as this can lead to broken belts and burned motors.

Note that the rocks in the drum should be close to the same hardness. Tumbling very hard stones with relatively soft ones will usually destroy the soft stones. The rocks should also be of various sizes as this aids in the natural action of the tumbler.

Also, while most rocks are suitable for tumbling, some are not. For instance, sandstones and most shale will break down too easily and don’t give a very good result. However, obsidian, quartz, and agates all give a product that can be astonishing in its beauty.

Prior to loading the drum, wash the rocks to remove any debris. An old toothbrush can be useful for this and subsequent steps. Load the drum, seal it, and start it tumbling. On dual tank tumblers, be sure to place the second tank on the tumbler as well, even if it is empty.

A day after the tumbler is started, stop it, release the seal on the tank, and allow gases to escape. It is normal for tumbling rocks to produce gases, especially early in each step, so this is done with each loading to prevent problems such as leaking tanks.

Once the tank is re-sealed, place it back on the tumbler and start it again. Allow the tumbler to run for about 14 days, then unseal and check the rocks in the tank. Rough edges should be worn away, and the stones should be fairly smooth. If they are not, they can be tumbled for another few days to a week.

Rinse the stones and use the toothbrush to make sure none of the coarse grit remains. The tank also needs to be rinsed out well.

NOTE: Do not rinse the stones in the sink. The grit can clog up sink drains quickly, and commercial drain clog preparations do little to correct this sort of plug.

Load the tank again, using medium grit instead of coarse grit, and repeat the process. Follow this with the fine, pre-polish, and polish grit, each done as above except that pre-polish and polish usually only takes about a week each.

When this is done, ordinary rocks can be transformed into objects of incredible beauty, suitable for prominent display in the home. Finding the stones for tumbling can be a lot of the fun, but seeing the finished product is often the reward, and often a surprising one.

It isn’t difficult to learn how to tumble rocks, and though it does take time to complete the whole sequence, it can result in true jewels that are things of beauty.