I have recently purchased a tumbler with assorted stainless shot and used about half a teaspoon of the abrasive soap powder that came with the tumbler, covered the load with water plus about an inch on top and left it on for a few hours. My silver disks, which have gold/silver granules soldered to them and the rest of my pieces all came out marred with tiny pits all over :O( It seems like the shot has marked the metal. Any idea why? I thought tumbling them would make them extra shiny as I had already polished them with the Dremel and rouge and expected a better, not worse result. I was hoping to not have to get covered in Rouge and have black fingers again... Can you help?
I'm not sure what the "abrasive soap" was, but the rotary tumblers we use are rock tumblers and sold as such. For jewelry, we "re-purpose" them to suit our needs by using stainless shot, water and dish-soap to gently tumble-polish our metal goods. Of course the sellers of the tumblers have no way of knowing what the machines are going to be used for. The abrasive powders used to polish rocks are damaging to metal. It is possible that the abrasives in the soap you used caused the marring and pitting.
While tumbling will remove slight surface blemishes, anything more serious will have to be polished out by hand. (sigh) Not fun! Try wearing tight-fitting (so the glove material does not interfere with the rotary tools) Nitrile disposable gloves for hand-polishing work to help prevent the rouges from being ground into your skin....saving lots of clean-up time and cleaner hands for you! Most disposable-style gloves will work, I've just found the nitrile ones to be a bit more durable.
So that you may enjoy the benefits of your tumbler, thoroughly clean the shot and the barrel until they are free from all of the abrasive residue. Use only water and liquid dish-soap. A de-burring or burnishing compound is better for some applications, but never use them on oxidized metal you wish to keep oxidized....eaves the oxidized metal a bit splotchy! Great for jumprings and findings with a bright-metal finish.