Having gone through three “Gyrock’s” in thirty years, the shot does
not go black on steel or stainless without human interference.
Try and duplicate what you did but this time throw the Job into
Bicarb of Soda with warm water before using the tumbler. If the
water fizzes up then you have not neutralised the acid remaining in
the (hollow) silver.
There are great soaps for tumblers, your shot shot will only give
you back what you put in. If your shot is dull put in shiny silver
and it will come out dull etc.
A soap can be made from pure soap so a Tech. Teacher said but the
finish on his shot said, sorry.
To get your shot back to normal polish you might need to tumble for
several hours twice a day over several days and then you will learn
to love your tumbler again.
Cheers. John S.