Although you could probably use any "low-sudsing" dishwashing or
laundry detergent, I have yet to find one as effective as those
specifically made for the purpose of tumbling. There are several
reasons for using the right detergent. One is lubrication. More
importantly it acts as an emulsifier, keeping dirt and oil in
suspension and allowing it to be easily rinsed away. This insures
the parts you are tumbling stay clean and that dirt, oil and
impurities don't interfere with the tumbling process. This is
particularly important when using cutting medias such as plastic
cones and pyramids which break down during the process. In a pinch,
I've used dishwashing detergent but I found I could not add enough to
do the job without creating a lot of suds. The low-sudsing
detergents made specifically for tumbling really do work best.
As far as picking stuff up in the pet shop for dry tumbling, I'd
suggest you screen it to remove the smallest particulate which will
otherwise get stuck in the tiny recesses of your jewelry. It's a
real pain to pick out. Don't try to wash it out. This stuff tends
to expand when wet making it even more difficult to remove.
Years ago I got hold of a dry media mixture from Germany. It was
composed of walnut shells (screened to about a 2mm size), plastic
balls (about the size of a pea), wood pegs, glass beads (about 4-5mm
diameter), felt cubes (about 1/4" square), and I can't remember what
else. The stuff worked great -- as long as you added some Simichrome
Polish. Unfortunately that company went out of business. But I got
into the habit of adding a variety of materials to my dry tumbling
media and results are mostly positive.
My recommendation would be to start with a base of standard dry
tumbling media such as walnut shells or corn cob made for tumbling.
Use Simichrome or other paste polish to charge it periodically. Use
only a tiny amount as you want the dry media to stay dry. Then by
all means experiment with additional materials (soft woods, plastics,
cob, etc.). Just be sure to screen it first. I think you'll like
the results generally.
The best media I've found is from Otec, a German company. Many
suppliers, not just Gesswein, carry this brand. Their "regular"
walnut shell is a dry media that removes very light scratches (as
from wear). Their "extra-fine" walnut shell produces an extremely
high finish. Used in the Otec disc finishers, it's the best finish
I've seen from an automated process.
VP Tech Services
Gesswein Co. Inc.
Tel: 1-800-544-2043 x287