When to Season: You’ll want to season, or coating the skillet with oil and baking it in the oven to create a nonstick surface, if your newly-purchased cast iron was not purchased pre-seasoned. If you see rust developing, if food is sticking to the surface, or it’s been washed improperly, you should re-season it.
How to Season: Preheat oven to 400 degrees. Using a paper towel or cloth, lightly coat the cast iron with a cooking oil. Place a drip pan on the oven’s bottom rack, and place the oiled skillet, upside down, on the top rack. Let cast iron bake in oven for one hour. Word of warning: doing this might make your kitchen smoky, so open a window!
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