Silver turned black in tumbler

For cleaning the stainless shot as well as the darkened barrel in a
rotary tumbler, I was told by a tech. at one of the supply companies
to put full strength sudsy ammonia in for cleaning. Tumble for 20
min. Rinse and repeat. This worked well. The patina I had used caused
a lot of messy build up and that took some work to eliminate.

Ruth Mary