I am sorry if this question has already been discussed here, but some of my medals are turning black, here are two examples (there are also others). Is there any thing I could or should do? It is better to leave them that way?
Thank you!
"Ideas are more powerful than guns. We would not let our enemies have guns, why should we let them have ideas?"
I would give them a wipe with a damp cloth, possibly a bit of soap, dry them off with another cloth and then place them into a protective environment (I use plastic envelopes).
As we do not know the prior history of the awards, they may have corrosive chemicals on them and most probably a good layer of mess from whatever they were smoking back in the U.S.S.R.
This is usually my first gentle step. Every case is different and depending on just how dirty the award is, it gets different treatment. I've baked some in the oven, used various chemicals (depending on composition) and certainly used plenty of soap and water.