Black matter is formed by oxidation-reduction reaction between metal components of stainless steel pot and oxygen after water is boiled dry. Cleaning the steel ball can remove the black surface. The white and black substances in the stainless steel teapot are not toxic, so you can continue to use the burnt stainless steel kettle. The products in the pot affect the perception, and long-term impurity will easily lead to the intake of precious metals. Therefore, stainless steel kettles should be cleaned regularly to ensure the safety and health of drinking water.