John mentioned a nifty book on this topic by James V. Stevens, The
Art and Science of Automatic Jewelry Finishing. It is indeed a great
book but is not in print nor likely to be, and Mr. Stevens died some
time ago. I found a copy (by the grace of God) while once meandering
through the Free Library in Baltimore (for those of you who may wish
to use Interlibrary Loan to peruse the book).
If you have a copy of Lapidary Journal, July 1999, there is a basic
article I wrote, “Tumble-Polishing Metal Jewelry.” In there, I
refer to my favorite tumbling medium, smooth brown irregular ceramic
pieces called “Cerambits” – I still have not been able to find
anything like them. The white ceramic balls which Rio sells are OK,
but they are a pain to use, since they bounce around (and escape)
when I’m pouring them in and out of the tumbler, and even the tiniest
ones do not quite polish corners, etc., as well as the Cerambits do.
If anyone knows where Cerambits can be gotten, please let me know!
I’d also recommend buying Judy Hoch’s book on tumble-polishing.
All the best,