Cast iron has a higher heat capacity than copper, so it takes more energy to heat a pound of cast iron to a given temperature than a pound of copper. More energy is stored in each pound of the cast iron. Aluminum has a higher heat capacity than iron (it stores more heat per pound) but is much less dense than iron. For a given volume, therefore, cast iron stores more heat than aluminum. Because cast iron pans typically weigh much more and are thicker than the same size pan in another material, they tend to store more energy when heated. This combination of high heat capacity and weight means that cast iron takes a long time to get hot. Once hot, however, a cast iron pan usually contains more thermal energy than other pans at the same temperature — a significant cooking advantage. Cast iron has unparalleled searing power because it has a lot of available thermal energy – and unlike almost any other type of pan, cast iron pans won’t warp when left dry on a burner to heat up. Thick and heavy cast iron will remain flat and true.Cast iron is slow to heat up, so it’s also slow to cool down. It is a good regulator. It retains its temperature longer than other materials and won’t produce temperature spikes. This behavior can be disconcerting to the uninitiated. Cooking with cast iron is more akin to driving a boat than a car: the pan doesn’t respond instantly to changes in the applied heat.