Copper is the best conductor of heat, especially for top-of-range cooking where the food must be cooked at precisely controlled temperatures. Copper cookware has about ten times the heat conductivity of stainless steel and glass and twice that of aluminum. It transmits heat evenly with great response, this makes it best for such high heat, fast cooking techniques such as sautéing and frying. Copper cookware, however, tends to react with foods. To prevent this most copper pans are lined with tin or stainless steel. A majority of copper pans today are lined with stainless steel rather than tin because it will last much longer. Copper cookware should not be placed in the dishwasher nor left to air dry as this causes spotting and they will have to be polished more frequently.