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Tumbler turning PMC silver black

I recently acquired an inexpensive rotary tumbler from Harbor
Freight. With stainless steel shot and Woolite, it worked great at
first. was tumbling PMC earrings and they came out clean and shiny.
Now they are coming out a blue black color. Help! I’ve tried a new
batch of shot, distilled water still black Thanx Pat

Silver gets black in a rubber tumbler when you use ammonia. Use
proper tumbling sopa, it gives a beautiful result, - forget the
price, its worth it.


Hi, How long are you tumbling the pieces for?

I’ve had problems if I forget and tumble stuff for 24 hours or
more, the shot and the pieces seem to abrade the walls of the black
rubber barrel I use, and this soupy gunk then discolours the silver
in the way you describe…so could this be the problem?

Steve Holden

I was told that the solution or the detergent used in the tumbler
can get contaminated and will turn silver black. It is not the
tumbler, the shot or the silver it is the chemical reaction of the

Let us now what solution you are using and if you changed any of the
polishing componds recently that has led to this problem.

Kenneth Singh