I was told by my friend that works in a bead store to clean my jewelry by putting it in a rock tumbler with a little warm water, a couple drops of soap and stainless steel shot.
Last night I did 4 batches, tumbled for about an hour each. The jewelry, was immediately clean and shiny.
It worked so well I did all of my clasps and silver beads that I have in my supplies to make jewelry. The stuff all looked brand new, shiny and ready to be incorporated into whatever I want.