A seasoned cast iron skillet is a cast iron frying pan that that has been treated to give it a protective non-stick finish. The seasoning process consists of using oil or solid fat such as lard to coat the skillet and heating it. This bakes the fat into the surface of the pan and allows it to fill in all the crevices creating a smooth surface. Many cooks prefer using a seasoned cast iron skillet because of this surface and because the cast iron material spreads heat out evenly and retains it well. Cast iron is also very durable and will last for an extremely long time with proper care.
When a cast iron skillet is purchased, it's not usually seasoned yet and will have a dull grayish finish. There are a few brands that are starting to sell already seasoned skillets, these will look black. The most common sizes for skillets are 10 inches (about 25.4 cm) and 12 inches (about 30.5 cm). Seasoned cast iron skillets in these sizes are versatile cooking tools. They are large enough to cook quantities of food, but small enough that most people can easily lift them with one hand.
After purchasing a new cast iron skillet, it should be washed thoroughly to remove residue from the manufacturing process; once it's clean, it needs to be seasoned. The skillet should be coated with a thin layer of fat, such as lard or oil, on all surfaces inside and out. It's important to season all surfaces because the seasoning protects the cast iron from developing rust. After the skillet is coated it should be placed in a warm oven, approximately 350 to 400°F (about 176.6 to 204.4°C), for about one hour and then allowed to cool. This process can be repeated a few times if desired.
The seasoning process bakes the fat into the surface of the seasoned cast iron skillet. The fat fills in any crevices or scratches and creates a smooth non-stick cooking surface. After a while, a well-seasoned cast iron skillet develops a smooth black finish with a soft shine, also known as a patina. This finish prevents food from sticking without the possible dangers of non-stick coatings that can wear away and flake off, contaminating the food being cooked.
In addition to the non-stick properties, many experienced cooks prefer a seasoned cast iron skillet because the metal distributes heat evenly and retains heat well. These pans are extremely durable and can last a lifetime with a low-maintenance care routine. After cooking in a seasoned cast iron skillet, it should be washed while it is still warm with hot water and little or no soap. It should be dried with paper towels and stored in a dry place free from moisture. With frequent use and proper care, it should last for years.