Stone polishing is not only the simplest of the lapidary arts, but also the least expensive. It requires little skill and minimal equipment, only a stone polishing machine and grit to tumble with your rocks. It can take several weeks as well as a number of grit changes, but at the end of the process, you'll be rewarded with shiny, polished rocks. You can use these rocks in jewellery designs, works of mosaic or sculpture art, interesting craft creations or simply as decoration.
Stone polishing machines, or tumbling machines, use abrasive grit and polishing compound, soap, water and movement to smooth the surface and edges of rough stones. During the tumbling procedure, you will use progressively finer abrasives, followed by a polishing compound, then soap, agitating the rocks until they are highly polished. This process mimics what naturally happens to stones in a stream or on the beach, but achieves a much brighter polish and shine.
Types and Features
Two types of polishing machines are available: the rotary tumbler and the vibratory tumbler. The rotary tumbler consists of a barrel-shaped container that holds the abrasive grit, water and rough stones you wish to polish. You seal the barrel and place it on a small machine that rotates it, smoothing and polishing the stones. The vibratory tumbler, on the other hand, consists of a bowl that mounts on top of a small vibrating machine. This type of machine polishes the stones by shaking the materials instead of rolling them over each other.
Rotary tumblers are the most popular type, according to Geology.com. They are usually less expensive than vibratory tumblers and will smooth angular stones into rounded ones in five or six weeks. Vibratory tumblers are faster, processing a batch of rocks in about one or two weeks, but they will not smooth and change the shape of the stones. Rocks polished in vibratory machines will have a shiny surface, but will retain their angles and edges. Because the bowls of vibratory machines often don't hold up well to very coarse material, they are often used only for polishing already-tumbled and shaped stones.
Stone tumblers must run non-stop for days on end and are very noisy. Some rotary tumbler manufacturers produce rubber barrels for their machines, which can minimise the noise. But if you're using a rotary tumbler with a steel or plastic barrel or are using a vibratory tumbler, you will need to take steps to quiet the racket. Placing the machine in a secluded room or basement can help. If you have neither of these, you could try putting the machine in your garage and covering it with a cardboard box lined with foam board or topped with an old blanket. This should reduce the noise considerably.