Dirty Stainless Steel Clue

I wrote just a short week ago about my Lortone rubber barrel tumbler.
I do a three step polish of my cast pieces. Rio’s medium and fine
plastic media two hours each , final step is stainless steel one to
two hours. All was going well for four weeks. Then suddenly the
sterling silver pieces came out a gun metal grey. It seemed sudden.
Several of you wrote and I tried several things to clean the stainless
steel. Dawn dish soap once, Coke Classic once. The shot seems
reasonably clean. So I then put some new cast pieces that I had just
oxidized, in Liver of Sulfur, in the rotary tumbler with the clean
stainless steel shot and Rio’s descaler. Oh I also had a chain that
was a little dull so threw that in also. On hour later I took them
out. Now this is strange: the chain was lovely, shiny and bright,
the other cast pieces that had been in the Liver of Sulfur was the
dirty gun metal color. So now I have a clue but since Liver of Sulfur
is the only oxidizer that I have ever used I am not sure why this
happened. Any clues? Coit PS: I would love to get this figured out but I
have gone ahead and used my buffer to do the polishing so I am not in
a panic as before.

Coit, The problem may be the rubber tumbler. I had the same problem a
couple of years ago, but I wasn’t using any steel shot in the
tumbler. About a week later, I received Charles Lewton Brain’s book
of shop tips and I noticed that one of the tips was not to use
vulcanized rubber tumbler barrels because they discolor the silver.I
ended up putting everything in some Tupperware that fit inside the
rubber barrel.Not the best solution since the Tupperware is
completely round instead of octogonal like the original barrel. It
might be easiest to just buy a plastic barrel and keep the rubber one
for tumbling rocks. Susan Hoge

I use a rubber barrel and tumbling soap - which I believe to be pure
soap - no detergent. (It looks remarkably like the OLD Ivory soap for
washing diapers) The Gesswein catalogue warns that burnishing compound
is not compatible with rubber barrels.
Karen