I am a bit confused. It is widely recommended that copper pans be lined with tin or stainless steel. Yet an unlined copper jam pan is regarded as being the absolute best pan for cooking jam. What gives? Having just received such a jam pan, I would like to know why this is so. Also, unlined copper mixing bowls are also widely used. What else can unlined copper cookware be used for? What are the rules for using unlined cooper?