15/03/2021
Cast iron pans DON'T heat evenly
The Theory: Searing steaks and frying potatoes requires high, even heat. Cast iron is great at searing steaks, so it must be great at heating evenly, right?
The Reality: Actually, cast iron is terrible at heating evenly. The thermal conductivity—the measure of a material's ability to transfer heat from one part to another—is around a third to a quarter that of a material like aluminum. What does this mean? Throw a cast iron skillet on a burner and you end up forming very clear hot spots right on top of where the flames are, while the rest of the pan remains relatively cool.
The main advantage of cast iron is that it has very high volumetric heat capacity, which means that once it's hot, it stays hot. This is vitally important when searing meat. To really heat cast iron evenly, place it over a burner and let it preheat for at least 10 minutes or so, rotating it every once in a while. Alternatively, heat it up in a hot oven for 20 to 30 minutes (but remember to use a potholder or dish towel!)
The other advantage is its high emissivity—that is, its tendency to expel a lot of heat energy from its surface in the form of radiation. Stainless steel has an emissivity of around .07. Even when it's extremely hot, you can put your hand close to it and not feel a thing. Only the food directly in contact with it is heating up in any way.
Cast iron, on the other hand, has a whopping .64 emissivity rating, which means that when you're cooking in it, you're not just cooking the surface in contact with the metal, but you're cooking a good deal of food above it as well. This makes it ideal for things like making hash or pan roasting chicken and vegetables.
Kenji Lopez's
There's a mysterious, myth-packed lore when it comes to cast iron pans. On the one hand there's the folks who claim you've got to treat your cast iron cookware like a delicate little flower. On the other, there's the macho types who chime in with their my cast iron is hella non-stick or goddam, does...
