This only works effectively on sealed pieces as they don’t tarnish much. As sealed pieces simply tend to dull with time, a good buff with the polishing cloth can remove the dullness and make the copper gleam again. However, you can slow down the tarnish on even non-lacquered pieces by giving them a quick polish with a jewelry polishing cloth before and after you wear it to keep it shiny and minimize tarnishing.
Squeeze the juice of one or two lemons into a cup and add some salt into it. Place the copper jewelry into the lemon juice and leave it for several minutes. If necessary, use a soft brush or cloth to rub the lemon to get rid of all the tarnihs. Rinse with water thoroughly and dry your copper jewelry. Don’t use metal containers for this method. Always use glass, ceramic or plastic.
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...
Regular ketchup works like a charm to get rid of copper tarnish due to the vinegar in the ketchup. Squeeze some ketchup onto the copper piece and rub until the tarnish is gone. You can use your fingers, a cloth or even a small soft toothbrush. Rinse well to get rid of all the ketchup.
Make a paste by mixing baking soda and lemon juice in equal amounts. Rub this on your copper jewelry using your fingers or a cloth. For a deeper clean, use a soft toothbrush. This works very well on elaborate pieces with lots of crevices. Rinse the paste of thoroughly and dry.