Hi Linnea -
First, all the dry medias are formulated for vibratory machines only
and is not appropriate or even useful in rotary machines.
I have found a really good dry media for cleaning up jewelry. It's
called Vibra-Dry+ and is available from Diamond Pacific. I haven't
tested it with pearls and opals, but their tests, that I saw, were
way more than satisfactory. It's an odd combination of organic stuff,
it looks like walnut shell, wood pieces, garbanzo beans, rice and
what makes it work - very fine diamond grit. It is being used by
jewelers for cleaning jewelry set with stones to clean it up and
remove tarnish. My only caution would be that it is very likely to
remove darkening or patinas pretty much everywhere. I'd buy the
50,000 Vibra-dry+. But if you have really bad tarnish, also get the
14,000 and run it first and follow with the 50,000.
To polish chains - run no more than three at a time. If you run
more, they will tie themselves in knots. Haven't had it happen with
three or less.
As to the Green buff - it is a chrome oxide mixed with wood chips
and walnut shell and is for white metals. The red buff is iron oxide
mixed the same and is for yellow metals. Neither is particularly
aggressive in my experience. I mostly use Simichrome in dry media and
it works for both white and yellow metals. I'm going to load up my
dry vibe with 50,000 right now - it is a lot less messy.
If you don't have a vibratory tumbler, look at the little
Vibra-sonic. It is great for small batches, is small and affordable.
I don't like it for steel.
The technical director at Diamond Pacific is Don Depue and he is
very helpful. http://www.ganoksin.com/gnkurl/1wk