First, the black specks you see coming off into your food are not harmful. They are most likely carbon deposits. This happens due to overheating of fats and oils. Using an oil with a low smoke point will carbonize at high temperatures and cause residue from the pores of your pan to rub off onto your food.
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.
The Fix: To remove any loose flakes, lightly scour the cookware, then season it by rubbing the pan with a thin layer of oil, placing it in the oven upside down, and baking for one hour at 450-500 degrees F.
The “black stuff” you see is a result of burn marks, dirt, dust, spray starch and fabric fiber buildup. Additionally, if you leave water inside your iron, it could begin to rust cause rusty spots. It's important to maintain your iron to avoid it from damaging or ruining your clothing.
To clean the cast iron skillet, rinse it first under hot water to remove any excess food or residue. Then, use a wet, clean paper towel to wipe out the inside of the pan until it's fully clean. Easy enough!
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.
Sometimes layers of seasoning may flake off your cast iron pan. This can happen if layers of seasoning have not fully bonded to 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.
Seasoning Cast Iron
The interesting thing about cast iron is that the more you use it, the more seasoned it will become. However, as you use and clean it, it's important to habitually reseason a pan to give it a fresh, clean layer of seasoning to aid with cooking and to protect from rust.
Common cooking oils like olive oil will gradually produce seasoning, but won't be as effective as grapeseed oil. Canola, other vegetable oils, and shortening are a little better.
Brown or black spots are normally a layer of carbonization which causes food to stick to the pan during cooking.
The black residue on a cast iron skillet isn't harmful; it's just a part of cooking with a cast iron pan. A black seasoned coating shouldn't rub off easily or affect the food, as it should form a useful non-stick surface for cooking. If residue starts to build up, however, this can affect your cooking.
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.
Put the oiled pan in a preheated 450°F (230°C) oven, and leave it there for 30 minutes. It may get a little smoky, so keep your kitchen well ventilated.
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.
Toothpaste. Dab toothpaste on residue spots on the soleplate and wipe them away. With your iron off and cool, smear a bit of toothpaste directly onto brown, sticky, or dirty spots and leave it to sit for about a minute. Then, use a clean cloth to wipe the toothpaste away.
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.
This means that the black oxide is not deposited on the surface of the substrate like nickel or zinc electroplating. Instead, the black oxide coating is produced by a chemical reaction between the iron on the surface of the ferrous metal and the oxidizing salts present in the black oxide solution.
Scrub and wash your pan
Scour the rusty sections with steel wool or the Lodge Rust Eraser. Then wash the pan with warm, soapy water. This step may remove portions of the seasoning, but that's okay because we're preparing to re-season the pan.