Pour vinegar into a glass or plastic bowl and submerge your copper jewelry in the vinegar. Add some salt for a deeper clean and leave the copper to soak for 15 to 20 minutes. When you take it out, your copper should be sparkling! Give it a good rinse to wash off all the vinegar and then dry it with a soft cloth. If the copper piece has gemstones, then take care as soaking in acidic vinegar can damage the stone. In that case, it is best to skip both this method as well as the lemon juice dip, and try one of the others.