Seasoning Cast Iron
Place the pan on the stove and warm it gently over low heat. Pour a tablespoon of good quality vegetable oil into the pan, and rub it all over the surface with paper towels. Heat the oven to 300 and place the pan inside for about one hour, long enough for the iron to fully absorb the oil. Take out the pan, let it cool and rub coarse salt onto the surface. To finish, rinse the pan with warm water and dry. In the future, never use soap to clean the cast iron. Just one washing with a harsh detergent could be enough to dissolve the finish you've worked so hard to achieve. Instead, rinse the pan with warm water. use coarse salt to remove any stubborn grease spots. Source: Martha Stewart