When cast iron skillets are exposed to high heat, several things happen:
Expansion: Cast iron has a relatively high coefficient of thermal expansion, meaning it expands when heated. As the skillet heats up, the metal expands, and this expansion can cause the skillet to become slightly larger.
Retention of Heat: Cast iron is an excellent conductor and retainer of heat. When exposed to high heat, the skillet absorbs and holds onto the heat, distributing it evenly throughout the cooking surface. This property makes cast iron skillets great for searing and cooking food at high temperatures.
Seasoning and Polymerization: If the cast iron skillet has been seasoned properly, which involves coating it with a layer of oil that is baked onto the surface, the high heat can enhance the seasoning. The seasoning forms a natural non-stick coating on the skillet, making it more effective for cooking and preventing rusting.
Changes in Color: With repeated exposure to high heat, the surface of the cast iron skillet can change color. It may become darker, which is a sign of the seasoning getting more seasoned and polymerized.
Warping: Although cast iron is a very durable material, exposing it to extremely high temperatures or rapid temperature changes can cause warping or cracking. For instance, placing a cold skillet on high heat suddenly may lead to thermal shock and damage.
Improved Cooking Performance: High heat helps in creating a nice crust on foods like steaks and potatoes, enhancing the flavors and textures of the cooked items.
It's important to note that while cast iron is excellent at retaining heat and providing even cooking, it can also get very hot. Always use appropriate oven mitts or handles when handling hot cast iron to avoid burns. Additionally, after cooking, it's essential to allow the skillet to cool down gradually to prevent thermal shock or damage to the seasoning. Proper care and maintenance, such as regular seasoning and avoiding harsh cleaning methods, will help prolong the life and performance of a cast iron skillet.