My good friend sells 100's of these (I am not joking!). I printed a small cute note than she adds to each set. It says 'microwave soup potholder. use for reheating not cooking'. We have tested with 4 and 5 minutes, but we feel it is safer to recommend no more than 3 minutes. Obviously, everything is 100% cotton - no poly anywhere. FYI - my kids love to use them to hold their ice cream bowls!