Bottom: SIGMABOND® patent of pressing technology for the cookware bottom, which can be used in all sorts of cooking ranges for example when cooking with middle and small fire. The warm-keeping function saves energy. Surface polishing: the inner side has been treated with smooth-satin, to prevent scorching. It can be used with any other cookware. The outer side has been treated with a satin-finishing, which prevents the cookware from being soiled and scorched.