Clean a cast iron frying pan immediately after each use by hand washing and drying it. If you choose to use soap, choose a mild dish washing liquid. Season the pan with enough vegetable oil to leave a shine without causing it to feel sticky. Do not place the pan in the dishwasher, use metal scouring pads or harsh detergents, as these can remove the seasoning that keeps foods from sticking to the metal.
With care, a cast iron pan can last a century or more. It does not have the chemical coating found on nonstick pans, which often begins to peel within a few months of purchase. Even when cast iron has been abused, it is often possible to clean the surface and reseason the pan so it is ready for use again.
Rusting pans, a dull gray coating or food that sticks to the pan indicates the need to reseason it. Clean any rust from the pan and wash it thoroughly using a brush and hot, soapy water, rinse it in hot water, and dry thoroughly. Melt a small amount of vegetable shortening, coat the pan and place it face down on the upper rack of an oven with the bottom rack covered in aluminum foil to contain any dripping fat. Set the oven to 350 degrees Fahrenheit and bake the pan for at least an hour.