There are passageways I can't get sandpaper and wire brushes into.
What solution would you use?
Googling I discount the lemon juice and baking soda ideas as too weak (fine for jewelry though).
I think they're copper sulfates or maybe copper oxides or maybe even copper carbonates, each of which may react differently to acids and ammonia.
Looking for industrial strength solutions I see people advise vinegar (which seems to weak to me) or maybe even muriatic acid (which seems too strong), or maybe even ammonia. http://www.rangefinderforum.com/forums/archive/index.php/t-25046.html
Which do you use?