The machine is used to rotate the barrels, they are available in many sizes which cater for large or smaller quantities of rock.

On the right you will see a picture of one of my favourite types of tumbler, it cost around $150 and has been running for over two years almost without stopping and certainly without any faults.

Each of the two horizontal bars support the barrel as it rolls around.  You can see that it has quite a good length on the supports, and can therefore hold more than one barrel at the same time.

Smaller versions are available at half the length, and larger machines are also available - although these are more often used for mass production.

Barrels

Your barrels will hold the rock as it turns on the machine - week after week.  They are normally made of a hard type of plastic with a softer lid which can be removed when placed in boiling water for around 3 minutes.

The barrel on the right can hold up to 3 pounds of rock, and the tumbler shown at the top can carry two of these barrels.  I have found that barrels half of this size are as small as is generally available, and much larger barrels and machines are also availabe.  This size however, can produce an adequete amount of polished stone for a small to modest collector.

Note that these barrels do not last forever, they tend to be worn down by the grit and stone and must be disposed of after around 1 year of use.  Eventually they crack and the contents seep out over your tumbler, creating a real mess - especially once the slurry hardens!

You will need one barrel for each phase of the process.  This means that 4 barrels are required.  (See the process for the reasoning behind this.)

Silicon Carbide Abrassive Grit.

For a given cycle you will need a minimum of Three types of grit.  The grit most commonly used is "silicon carbide", and can be purchased in most good rocks and minerals type of store and some comprehensive hardware stores.

Grit is gauged by the size of the particles and different sized particles perform different tasks during the cycle.  You will need the following sizes :-

One tub of 80 grit, one tub of 220 one tub of 400. 

The larger the "number" or rating of the grit - the smaller the particles - and therefore the smaller scratches result on the material you are tumbling.

On the right you can see two different sizes of tubs of grit, but many more brands are available - the thing to remember when out shopping is that you need one tub of each of the above grades and the material is "silicon carbide".

Cerium Oxide Polish.

Once the grit has done its work removing all the rough edges from the raw material, the stones are placed inside a completely fresh barrel along with water and Cerium Oxide.  It is this final step which produces the "glassy wet" look of your tumbled stones. 

The polish is available from the same place you get your grit, and normally comes in the same type of tubs as shown above right. 

Expect to use only a fraction of the amount of polish as you do grit - with this in mind a smaller tub can be purchased.

Round Plastic Pellets.

During the tumbling process - rocks of different sizes strike each other with often damaging  impact causing a burring effect.  This must be minimised - especially during the later phases (2 and 3) of grit and essentially during the polish Phase (4).

The plastic pellets are inserted into the barrel with the stones and grit/polish to protect them during the cycle.

On the right I have circled areas where there is damage to the stones due to an insufficient plastic pellet quantity in the barrel.  Damage normally occurs on the outer corners as you can see, but also around weak points in a stone where natural cracks and crevices allow the grits to penetrate deeper during impact. 

The pellets are hard enough to prevent damage, but not hard enough to cause chipping or scratching to even the softest stone.  The diameter of the pellets should be expected to be around 3-4 millimeters.