To keep the flash in copper pans, try these polished tips from Better Homes and Gardens Country Kitchen Ideas magazine:
First, there's a difference between cleaning a copper pot and polishing it. One is a necessity, the other a preference. Clean tin-lined pans (easier and less expensive to reline than nickel-lined pans) in hot, soapy water using a soft cloth or pad; wipe dry.For a shine, use a metal cleanser on the exterior that's suitable for copper. Be sure to rinse well and dry thoroughly - water droplets left on the copper make those nasty little dark spots. And though the patina unpolished copper develops may be preferred, polishing once a year is a good idea. Remember: The more copper is used, the less it has to be polished. It's plain old air that does most of the tarnishing.