Bundaberg Gem & Mineral Society Inc
Club for Lapidary, Silverwork, Faceting, Enameling and Wirework in Bundaberg
TUMBLING
THE PROCESS OF TUMBLING
Tumbling is the process of placing rocks (these may be preformed beforehand or not) into a machine, that you will take through different grades of course sanding material and eventually polishing material. A tumbler may be a cylinder that rolls the rocks over and over within it, or it may be what is known as a vibrating tumbler, which just vibrates the rocks. When done in a vibrating tumbler, you are more likely to end up with flat sided rocks.
Tumbling is a good way to use up those small pieces and chips that are too small for cabbing or are already chipped and cracked.
STEP ONE
1. Select stones of a similar hardness or type. Stones should be clean and may be of varying sizes.
2. The tumbler should be at least 75% full of stones, but no more than 90% full.
3. Add enough water to just cover the rocks.
4. Add one laundry scoop of the 80 grit to the tumbler barrel and seal it.
5. Put the barrel on to the tumbler rollers and switch on. Check to make sure that your barrel is not leaking, tighten barrel seals if needed. Let the tumbler run for approx. 48 hours and then open to release any pressure that may have built up. Check to see if stones are grinding and if necessary add a little more grit. Return barrel to rollers and let run continuously for a week before checking again. If you are happy with the stones at this point proceed to next step, if stones are not smoothed off enough return the barrel to the rollers for a further week. This first step in the tumbling process can take up to three weeks.
STEP TWO
1. Wash all the stones and the barrel thoroughly to remove all of the 80 grit, discard the used grit. If this is not done you will not get a good finish on your stones.
2. Return the clean stones to the barrel and proceed as in step one using the 400 grit. Tumble until you are satisfied with the finish on your stones.
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STEP THREE
1. Wash and thoroughly clean stones and the barrel before proceeding with this final stage.
2. Return the clean stones to the barrel and continue as before using a polishing powder in place of the grit. Check after a week to see if the stones are polishing and continue until you are satisfied with the finish. Wash and clean the stones and the barrel thoroughly. Enjoy your finished stones.
If your tumbler has two barrels it is recommended that you use one for polishing only and one for the grinding process. After your initial tumble you will be able to have some tumbling while others are polishing.