Steve, most of my jewelry is cast and ALL of it is tumbled with steel
shot. I have always thought the same about how it stays clean longer,
and assumed it was the Sunsheen burnishing solution I use (from Rio).
Can't prove it.
But now someone might tell me something. After several people
reported using Simple Green as a tumbling solution, I tried it a
couple times. It seemed to turn not the silver, but the stainless
shot dark. Anybody know why or whether? I stopped using it, anyway.
Stick to cleaning around the house with that.