I have been cleaning a students sterling silver chain maille
bracelet which was left in a commercial jewellery cleaning fluid
while she went on holiday, the solution dried out and the jewellery
became coated with a thick black and rust coloured deposit. In the
cleaning fluid was a mixture of jewellery, gold, sterling and
Tumbling has removed all of this deposit, some of the chain is now
it’s original sparkling silver, but some of the chain has patches of
a light copper colour as though it has been very unevenly copper
plated. Some rings in the chain are now both silver and copper!!!
Why and how has this copper stain appeared on the sterling silver
and is it possible to remove it.