Hi Daniel, On occasion my pickle solution will get contaminated and
turn everything a nasty reddish color. ( I suspect soft solder...lead
maybe...on something like a charm that I did not see)
Anyhow, I don't know the chemistry or why it works but if I soak the
pieces in Connoisseurs Silver Cleaner 3-5min. it removes it very
well...This has saved me with rope necklaces and the tinsel necklaces
that are very difficult to polish inside.
Jewelry stores usually sell this stuff in small jars.
(inexpensive)...You don't need a lot. To buy it from a supplier you
might need to buy a case.
I hope this helps,