Do as much hand-finishing as possible. The tumbler
will polish the surface but if there’s a scratch it will still be there
(and maybe even more visible!) when you pull it out. When I hand-finish I
sand up to 1200 or 1500 grit and then use a white polishing pad before
tumbling.
Do NOT set your stone. Tumbling is probably okay for
some harder stones, but it can harm softer stones – especially
turquoise, pearl, amber, malachite, etc. And if you have a hard stone
and a soft stone in the same tumbling session, the hard stone might
affect the softer one. I know a lot of people who tumble their piece
after setting the stone and they feel that it’s safe. Personally, I
prefer not to risk it. So, experiment if you want to but be aware that
some stones may dull in the jewelry rotary tumbler.
Optional: Oxidize your piece and wipe off the surface
patina with a white polishing pad. Tumbling will clean up your metal and
some of the patina will be removed (especially if you leave it in for a
long time), but most of the time the patina stays in the recessed areas
and looks great!
Put your steel shot and your jewelry in the drum. Fill it with water just about an inch above the contents.
Add a burnishing lubricant. In this case, I mean Dawn dish soap. A small squirt will work. The instructions of jewelry magnetic tumbler that come with the tumbler say “no more than two drops” but I’ve used more with no problems. Too much and it’s just way too sudsy. I’ve also heard Simple Green works well. Stay away from abrasive or citrus cleaners as they might eat away at the rubber drum.
Close up the drum, set it on the rollers and plug in. Leave it to tumble for at least 30 minutes. Two hours is usually good. You can tumble as long as you want but there is a point where you may be removing fine details so be sure to check it now and then.
When it’s done, pour everything into a strainer over the sink. Rinse it well. Pour it out onto a tray lined with paper towels and pull out your pieces. Be sure to allow the shot to dry thoroughly before storing it away.