In response to a very tarnished copper byzantine chainmaille bracelet, I started looking for a liquid cleaner (polish is tough to get out of all those little nooks and crannies..... sounds like I'm talking about English muffins.) I have soaked the bracelet in vinegar (which requires over night soaking and smells awful.) At Artbeads.com I found a spray cleaner called "Precious." It came today and I tried it immediately. Wow, it works instantly.
The cleaner is made for 14 and 18K gold, sterling silver, platinum and copper. Just spray it on, wait 30-60 seconds (if even that) and rinse it off. The only bad thing is that of course it is hazardous. (What isn't any more.) So, it has to be used with caution. (Try not to breath while cleaning your jewelry.) But the results are outstanding!