I just received a set of antique unlined copper pots as a gift from my aunt and uncle. I have tried all kinds of metal polish, washing, baking soda, lemon/salt, and the like, and the tarnish is mostly gone, but i cannot get rid of these little black spots inside. I have Bar Keeper's Friend, but haven't tried it yet, because it seems a little abrasive. I also looked at food52 copper care article, but no info on removing black spots. Any ideas? Did I somehow accidentally ruin them?