Very few jackets are pure copper, most are made of gilding metal 5% zinc 95% copper.
Those of you getting copper prices, spend it well, the boom won't last.
If you are useing water and soap try citric acid about 1/4 teaspoon to the gallon. Soap works good with citric acid.
Lemishine dishwasher detergent is a good source of citric acid. Avaliable at wall mart.