Slather a thick coating of ketchup all over your copper surface. I used Hunt's because it's what I had on hand but less expensive generic ketchup will work as well.
Rub the ketchup into any areas that are particularly problematic or have a thicker layer of oxidation. Let the ketchup stay on the copper for several minutes up to several hours but don't let it dry. The length of time you leave it on will depend on how much tarnish there is.
While the ketchup is still moist rinse the copper piece you are cleaning with water and wipe dry using a clean cloth (a microfiber cloth will work well) or a towel.
Depending on how tarnished the copper piece you are cleaning is, you may need to reapply a second coat of ketchup to some of the areas and use a scrubber to get the tough portions clean. Rinse thoroughly with fresh water in between treatments.
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As with any of my recipes, calorie counts and nutritional information varies greatly depending on which products you choose to use when cooking this dish.