Copper can be a finicky material; it tarnishes easily even when subject to normal wear. Fortunately, using only common household items that most people keep on hand, it doesn't take much to clean copper and renew its earthy and robust shine. Choose your approach from the following options based on the supplies you already have in your pantry.
SALT AND VINEGAR
It's a winning combination, not only as a flavoring for potato chips, but also as a cleaning solution for copper. Simply sprinkle salt over the object you want to clean, then thoroughly scrub it with a vinegar-soaked cloth. (Expect the cloth to get dirty as you work; if it gets really dirty, swap in a new one.) Once you have rubbed away all the tarnish, rinse the object under the faucet to remove the salt residue. At this point, the copper should be looking a lot better than it did.
Do dents and depressions in the copper still harbor hard-to-reach dirt and grime? If so, apply salt directly to those areas, then head to the bathroom and retrieve an old toothbrush. After dipping its bristles in the vinegar, use the toothbrush to scrub the dirty or oxidized parts of the copper that eluded your cleaning efforts the first time around.
If the steps above leave you frustrated, there's still one more thing you can try. In a large pot, mix one cup of vinegar, one tablespoon of salt, and four or five cups of water. Place the entire copper object into the pot, then bring the water to a boil. Leave it boiling until you begin to see the tarnish falling away from the copper. Once you've taken the copper out of the pot, it may be necessary to do some more scrubbing, but now it should be significantly easier to get results.
LEMONS OR LIMES
If there's no vinegar in your cupboard this week, you can rely instead on any number of common household acids-prime examples are lemon or lime juice. (But know that in a pinch, anything acidic, even tomato ketchup, can be used.) Cut the citrus fruit in half, sprinkle salt on its exposed flesh, then rub the lemon or lime against the tarnished copper. Finish by wiping the copper object thoroughly with a dry cloth, polishing away all the accumulations marring the surface, which the combination of acidity and salt should have effectively loosened up for you.