The pots and pans themselves will not turn yellow or black, but if the heating temperature is too high or the outside of the pots and pans are stained with grease or condiments heated, they may turn yellow or black. Please wash this product promptly with hot soapy water, rinse thoroughly, and then air dry immediately. It is best to apply some cooking oil to preserve.Please avoid using salt solution or acidic/irritating detergent to keep the surface treatment.