I clean the dishes in my house, and usually the toughest thing for me to clean is our copper-bottomed stainless steel pots and pans. Oil scorches onto the sides, and since we have an electric stove, the copper discolors annoyingly quickly due to resting right on the coil burners. Once, I overheated a 12″ pan for so long that the copper bottom actually turned grey.
But I wasn’t worried. I have Kleen King. This stuff is amazing. It’s got the same consistency as other powder cleaners, and it but it takes crust and discoloration off copper and stainless steel like a dream. It requires a little bit of water, and only the tiniest bit of elbow grease (as in, it’s necessary to move it around on the surface; you can’t just leave it there). I’ve rescued my own mistakes more times than I can count, and amazed new roommates by saving pots and pans they had left for dead.
They’ve also got versions for aluminum and enameled pots, though I’ve never used them.