Seasoning is a natural process and requires oil to be heated in the pan. The oil reacts with the iron, creating a visible black layer. You can build a seasoning yourself from scratch, but it's much easier to buy a preseasoned skillet set, like mine from Uno Casa.
Cast iron is typically black due to the presence of carbon and the way it is processed. Here are the main reasons: Carbon Content: Cast iron contains a significant amount of carbon (usually 2-4%), which gives it its characteristic dark color.
Generally, black oxide or black iron oxide refers to the oxide of iron known as magnetite (Fe3O4) that is formed when a ferrous metal is exposed to special oxidising chemicals. It is a type of conversion coating, thus the surface layer of a metal is formed into its oxide through conversion.
Bake. Place the cookware in the oven upside down on the top rack and place aluminum foil on the bottom rack to catch any excess oil that may drip off the cookware. Bake at 450-500 degrees F for one hour. Allow to cool and repeat as necessary to achieve the classic black patina.
Over time, dirt, dust, spray starch and fabric fibers build-up on the bottom soleplate of your iron. In addition, old water inside your iron's water reservoir can begin to cause rust spots. While you may be inclined to toss your iron for a newer, cleaner model, regular cleaning is relatively easy.
Your new skillet may be have been pre-seasoned to keep it from rusting in the store. This seasoning is not meant to last forever and can start to flake after the first few meals you cook. The oil or wax coating will start to disintegrate with high heat and will not hold up for long.
White vinegar – white vinegar can help you here, but check the manufacturer's instructions first as putting vinegar in the reservoir may not be recommended for your model. Mix equal amounts of vinegar and water, put the mixture in the reservoir, turn the iron to medium heat and give it about ten minutes to steam.
However, iron when exposed to a highly alkaline salt bath at about 285 degrees F forms the other oxide of iron, namely ferrous oxide, Fe3O4, which is an aesthetically appealing black oxide or what could be called black rust. In this sense, it's good rust!
Cast iron that's been taken care of by its owner will be regularly seasoned. This process leaves behind a jet black coating that not only stops a pan from rusting but creates a non-stick surface that's easy to cook on. Seasoning is a natural process and requires oil to be heated in the pan.
When selecting a seasoning oil, you want one that's high in polyunsaturated fats and has a high ratio of polyunsaturated fat to monounsaturated fat. Among common cooking oils, grapeseed oil and sunflower oil stand out for their high polyunsaturated fat content and desirable ratio of polyunsaturated to saturated fat.
Seasoning is the black patina that builds up on your cast iron skillet with regular use, a non-stick surface that's slick enough for eggs to skate across the pan, but tough enough to withstand the blazing heat needed to properly sear a steak.
Re-season thoroughly and often.
The best rule of thumb is to gently wash, dry, and apply a thin layer of oil after every use. When washing cast iron, I like to use a Scrub Daddy to gently scrub off any food debris with lukewarm water and a very small amount of soap.
Heat Exposure
Prolonged exposure to high heat can cause aluminum pans to discolor and blacken. "This can happen when cooking at very high temperatures (especially if the pan is empty or contains a small amount of oil or food)," says Alicia Sokolowski, the president and co-CEO of AspenClean.
Can I use steel wool or a metal scrubber to clean my cast iron pan? No! We recommend using a pan scraper or the Lodge Chainmail Scrubber to remove any stuck-on residue. We only recommend using steel wool or a metal scrubber to remove rust before reseasoning.
Make a paste using two parts baking soda and one part lemon juice, and then apply the paste to the rusty area using a sponge and allow to sit for at least 30 minutes. Use a brush or steel wool to scrub away the rust from the metal.
You should only need to fully re-season your cast-iron cookware one to two times a year, but you may also want to give it some extra seasoning love anytime you cook something that requires a heavy-duty cleaning.
This black residue from your cast-iron pan doesn't look great, but it's just seasoning and it's not harmful. Keep cooking in that pan, washing and drying and oiling it meticulously, and you'll see the issue clear up quickly.