Walk into any Williams-Sonoma and you'll see rows of absolutely stunning copper cookware, pinkish brown in its perfection and infarctingly high in its price. Eventually you give into the pan lust and drop several Benjamins on a set.
You get it home, cook with it a few times, and it turns a disgusting mottled brown. You ignore it and it develops burnt black spots on the bottom. You're too embarrassed to show it, so you shove your $600 investment to the back of a closet. Or maybe you go to the market to buy copper cleanser and you see the price tag (or the ingredients you're proposing to put on the cookware that's going to make food you intend to eat) and blanch.
The difference between the two pots in the picture to the right is ten minutes and about fifty cents' worth of all-natural cleaning products. How, you ask?
You'll need a lemon, about half a cup of kosher salt and a sponge or strong cloth. For really bad cases you may need a plastic scrubber (you can use steel wool, but be whisper-gentle with it, lest you scratch the copper).
Turn the pot upside down, rub it with a piece of cut lemon, then sprinkle salt on it. Rub gently again with the lemon and let it sit for three minutes. You may see an immediate improvement.
Now take your sponge, the “firm” side, and rub in circles. You may need to apply a little bit of elbow grease (i.e., work) to get some of it off, but after about two minutes, you should have all but the worst burns off.
Unfortunately, this is the hard part: using lemon, salt, the sponge and perhaps a plastic scrubber to work the burns off. Press down firmly with your thumb and rub in different directions. It may not go at first, but if you use the scrubber in one direction, you should be able to rub the same direction with the sponge and see an improvement.
Once you're done, wash the pot with soap and water and dry immediately… and for heaven's sake don't use the sponge on dishes until you've washed and sterilized it. If you do this every time (or, realistically, every other time) you use the dishes, you may find you don't need to scrub very much. I am not that dedicated; when it looks bad, I polish it.