In 1997 Terry Ensell and Julene Kanies wrote:
Regarding the vibratory tumbling instructions: I use 60/90 grit to start with. But, I did have my grinding bowl coated with Rhino Lining, which is the stuff they coat pickup truck beds with after I wore out a barrel after three loads when I didn't heed the part of the instructions that said not to do that.
As a matter of fact, I was able to have the same barrel coated that I had worn out. I have a 50-pound barrel and it cost me $25 to have it coated, which was cheaper than the $80 another barrel would cost, which you should have anyways for polishing only. It holds up very well even though it did seem quite soft, and it quieted it down a lot, which was great as it was very noisy.
I might also mention that if you have a barrel coated, you need to score, scratch, and abuse the hell out of the barrel before it is coated or it will peel off.
I grind for about three days with the 60/90 making sure twice a day that the slurry is not building up to a point where the rocks are not vortexing around the barrel. I add water as needed. If the slurry does get too thick then rinse it out and restart it. I check the rock and if it is not ground enough I redo the grit again and run it for two to three days again.
If it is hammer cracked rock you may find you need to do the 60/90 two to three times to get it smoothed up. Do not rush this step. If you are polishing river run rock, just the three days of 60/90 will do.
Then take the rock out and completely clean the rock, barrel, and lid. Add 220 grit and grind for three days checking twice a day to make sure slurry is not too thick, adding water as needed. Again, completely clean everything and go to 500 grit and do this for three more days and check it once again twice a day.
Now as I mentioned you really should use a separate barrel for polishing only. I use TXP for polishing compounds and usually get a great polish in one to two days. I usually just add some Ivory Flakes to the polish mix and then run it for about 15 minutes and rinse it out and let it dry out and you are done.
A couple of other things I might mention is that you need to have a variety of sizes of rock to get good grinding action, and you should have a rock of the same hardness. For the above steps, I have used agate and jaspers and have gotten good results.
Another thing I do during the first three grinding steps is to add a little Dawn dish detergent to the barrel to decrease surface tension and allow for better grinding action. If for some reason you are not getting a good polish, try adding plastic beads to the polishing cycle and check it again. If the results are still not satisfactory it may be that more attention needs to be paid to the cleaning between grits.
Terry Ensell & Julene Kanies <[email protected]>