If you buy the wire in the hardware store - it will be in isolation. I use stationery knife to remove this isolation.
The wire should be soft so as not to put pressure on it with great effort. If push strongly - tools left a deep dent.
I should also make sure that there is no cover on the wire. Otherwise, I can not oxidize copper.
Fold the wire in the ring and heat the gas burner until the red lights. Slide the burner all the time, so as not to melt copper.
When heated, appears yellow flames and smoke - it burns lacquer. Work under the hood, as smoke is dangerous to health.
After heating the copper changes color. It is black. But we can return purity copper with a solution of citric acid. This dietary citric acid, which is sold in supermarkets and grocery stores. 1 tablespoon acid half cup of water. Warm solution over medium heat until the copper is cleared.
Thus we get a soft, clean copper, which can be easily folded hands even without tools.
Very thin wire 29-24 gauge is better to buy uncoated.