Black steel (d) is inexpensive, conducts heat quickly, and does not warp under high temperatures. Used for frying pans, omelette and crêpe pans, woks, and deep fryers, steel pans are often not washed, as washing causes rust. In this case, the pan is wiped clean and then rubbed with salt to remove any remaining particles. The pan is seasoned with a light coating of oil after each use to retain its nonstick capabilities.