The surfaces of both of these nonstainless, iron-based metals are rather porous and have microscopic jagged peaks. You season a pan or pot by rubbing it with oil, heating it for 30 to 60 minutes in a 300 degrees F oven, and then cooling it to room temperature. The oil fills the cavities and becomes entrenched in them, as well as rounding off the peaks. Two culinary benefits result. First, the cooking surface develops a nonstick quality because the formerly jagged and pitted surface becomes smooth. Second, because the pores are permeated with oil, water cannot seep in and create rust that would give food an off-flavor.