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If you’ve used a Mr. Clean Magic Eraser, you know the results can be … well, pretty magical. These dense little sponges are actually melamine foam. (Hint: You can buy generic versions on Amazon for a lot less than retail.) They easily remove permanent marker, hard water buildup, soap scum and a host of other grimy messes. But — and it’s a big “but” — Magic Erasers shouldn’t be used on every…