Rock polishing is a fun and relatively inexpensive hobby. When you use a rock polisher, or tumbler as it is more commonly known, you are imitating the abrasive action of water on stones. Stones in a stream or in the ocean are worn smooth over time; the rock polisher uses grit and water to achieve the same effects much more quickly.
A rock polisher is easily located through a hobby shop or an Internet site. There are two types of polishers: vibratory and rotary. Vibratory tumblers are noisier and more expensive than rotary tumblers. They need to be monitored frequently. However, they will finish a batch of rocks in just over a week. Rotary tumblers can take four to six weeks to finish a batch of rock. They only need to be checked every day or two.
Vibratory tumblers can polish softer materials without crumbling them. Choose your polisher by the types and size of rock you will be polishing. Since the barrel must be filled 2/3 to 4/5 full, choose a tumbler with a larger barrel if you wish to work with larger rocks. If you wish to be able to polish more than one batch at a time, purchase a polisher with more than one barrel or hopper.
Give careful thought to where you will place the tumbler. Even rotary tumblers with rubber barrels make a certain amount of noise. Since barrels can leak from time to time, you will want a place that will not be damaged by water. You will also need a place to dispose of the slurry, which is the leftover material from the polishing process.
And you will need an electrical outlet. The temperature should be neither very hot, which will make the motor run hot, or very cold, which will make the motor work harder. Avoid a damp place. A basement or utility room is an ideal place, as long as it does not have extremes of heat and cold, and does not have excessive humidity.
You will need supplies for tumbling. The first is grit, which is used to help wear down the rocks. Grit is made of one of several substances such as silica carbide or aluminum oxide. There are several sizes of grit; it ranges from coarse (60/90 size) to medium (120/220) to fine (500 and above).
You may purchase a kit with each kind of grit, or purchase each type separately. You will also need plastic pellets or ceramic media. The pellets are used in the final stages of polishing, and also in the earlier stages to protect the rocks from chipping each other. Finally, you will need polishing compound to really make your rocks shine.
Rocks for tumbling can be obtained from the same place you bought your tumbler. You can also polish rocks that you have collected. Sort the rocks to be polished by type, size, and hardness, as the best results are obtained by polishing rocks of a similar size and hardness.
If using a rotary tumbler, fill the barrel with the rocks and either plastic pellets or ceramic media until it is about 2/3 to ¾ full. Do not fill the barrel all the way, or you will have no room for the grit and water. Add 2 to 2 ½ tablespoons of coarse grit per pound of rock. Add water until it is just below the top of the rocks, seal the barrel, put the barrel on the tumbler, and start the tumbler.
Check for leaks after the tumbler has been working for 10 or 15 minutes. Check on the rocks daily. After 7 to 10 days, the rocks should be rounded. Remove them from the barrel and clean the barrel thoroughly. Clean the rocks with soap and water, being careful to remove any traces of old grit. Never pour the slurry down your drain, as it will clog it. Dispose of the slurry in the trash.
For the second stage, put the rocks back into the barrel with enough plastic pellets to fill the barrel ¾ full. Add 2 to 2 ½ tablespoons of medium grit per pound of rock. Add water until it is almost to the top of the rocks and tumble for 7 to 10 days, checking the load daily. You are trying to remove any scratches left on the rocks by the first stage of tumbling. At the end of this state, clean the rocks and barrel as before.
For the third stage, add the rocks and some plastic pellets to the barrel. Add 2 ½ tablespoons of a fine grit per pound of rock and add water up to the just below the top of the rocks. Tumble for a week, checking on the rocks daily. At the end of a week, take a rock out of the barrel and polish is gently on a soft piece of cloth.
If the rock does not have a shine where it was rubbed, continue to polish the rocks. Check the rocks daily to see if they shine when rubbed. If so, clean the barrel and the rocks, being especially careful to remove all traces of the fine grit which will be harder to remove than in the previous stages.
For the fourth stage, place the rocks and plastic pellets in the barrel again. Add 2 ½ tablespoons of polishing compound. Add water until it almost covers the stones. Tumble for 5 to 7 days. When this stage is completed your rocks should look the same dry as when they are wet. Clean the rocks and the barrel very thoroughly.
For vibratory tumblers, the stages are similar, except that they will take less time. Also, the hopper of the tumbler should be filled ¾ to 4/5 full, and the amount of grit used is 1 ½ to 2 tablespoons of grit. The first stage will take 1 to 2 days. The second stage will take 2 to 4 days. The third stage will also take 2 to 4 days. The fourth stage is different than the fourth stage for rotary tumblers.
In this stage, use extremely fine grit, such as 600 grit aluminum oxide. The aluminum oxide is gentler than silicon oxide and will give a more rounded surface. The fourth stage will take 1 to 2 days. An optional fifth stage is to use 1 ½ tablespoons of polishing compound per pound of rocks for 2 to 4 days. Be sure to clean the rocks and the hopper very well after each stage.
