Hello: Catching up on e-mail …this reply may be too late for use.
Judy Hoch, she of the Tumbler manual, recommended not tumbling
anything with stones or pearls. She said the questioner might be
able to get by with tumbling with walnut shell charged with
compound, but that the pearls might pick up color.
I tried this as a test, having a big batch of tarnished silver/pearl
jewelry returned from consignment, and wanting to find the best
method before risking the lot. I tumbled in dry sawdust charged with
rouge. The pearls did come out pinkish. Under magnification, red
grains were embedded in the pearl. It was not possible to wash them
out. Pearls are porous, and have a microscopic texture, whether you
can see it or not.
You could probably tumble white pearls with a white compound, as
long as you don’t mind the fact that they will still have white
compound embedded in them, which will do who-knows-what over time. I
believe it will affect the luster, permanently. Try a test piece in
plain walnut shell, for a longer run time. The light texture of the
walnut shell might be enough, if tarnish is not too bad. Keep it
mind that walnut shell or sawdust will work their way into every
unimaginable crevice, such as bead holes, and you may spend a long
time picking it out.
Cheap walnut shell source! Pet supply store; sold as bedding for
reptiles. Husband came home with big bag for daughter’s pet lizard.
I pounced and commandeered half the bag; 1/4 the price, no bulky