Overheating or allowing the cookware to boil dry can cause yellow, brown, dark purple, blue or rainbow tints on the stainless steel surface. These tints although harmless, can make the pan less appealing. To remove this discolouration, use our Nutricraft Stainless Steel Cleanser with a wet non-abrasive cleaning pad. Wash with warm soapy water, rinse and dry. The discolouration is not covered under your product warranty and does not affect the performance of the cookware.