Normally, cast iron skillets must be treated before they can be used for the first time. This process, called seasoning, gives the iron its nonstick properties and protects it from rust. Seasoning involves coating the skillet with a thin layer of vegetable oil, then baking it in the oven. Pre-seasoned skillets are treated at the manufacturing plant, so they can go directly from the retailer to a stove burner with nothing more than a hot rinse to remove dust.
While some people enjoy the ritual of seasoning their own skillet, a pre-seasoned one guarantees a good start. This type of cookware is evenly sprayed with oil at the manufacturing plant, then baked at high temperatures to allow the oil to seep into the pores of the metal. Skillets that are already seasoned are black, while unseasoned ones are typically silvery gray in color.
People who have bought an unseasoned skillet and given it that first seasoning themselves might remember the result was a caramel-colored pan. With subsequent seasonings, the pan eventually turned black. Pre-seasoned skillets eliminate the “running start” to get the iron cookware initially protected and useable. Not only is it a time-saver for cast iron aficionados, but it’s reassuring to novices to know that their skillet has been correctly seasoned.
Just because a skillet has been seasoned at the factory, this does not mean that it will never again require seasoning. Any cast iron cookware must occasionally be re-seasoned to maintain the nonstick surface and protect the pan. Soap is not recommended for cast iron, as it can remove the seasoning, although some people choose to use mild soap anyway. Re-seasoning should take place after the pan has been washed with soap, or whenever the pan starts to lose its nonstick properties.
When a skillet is new, even if it has been pre-seasoned, it should be re-seasoned more frequently than an older skillet. The more a cook uses an iron skillet, the better the nonstick surface, as cooking itself seasons the inside of the pan. Pre-seasoned skillets and cookware cost a few dollars more than unseasoned cookware, but shoppers who are new to cast iron will probably find that it's worth the price difference to know the initial seasoning has been an excellent one. Cast-iron can easily last a lifetime with proper care, and it is among the least expensive types of cookware. Despite its lower price, many professionals count cast iron among the best pan choices.