They are most likely carbon deposits. This happens due to overheating of fats and oils.
This black residue from your cast-iron pan doesn't look great, but it's just seasoning and it's not harmful.
The black residue or black specks coming off your cast iron cookware is carbon deposits formed during the cooking process. It is generally created from overheating of cooking oil or fats used while cooking, or bits of burnt food that accumulate in the pores of the cookware.
The black residue or black specks coming off your cast iron cookware is carbon deposits formed during the cooking process. It is generally created from overheating of cooking oil or fats used while cooking, or bits of burnt food that accumulate in the pores of the cookware.
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.
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.
If vinegar alone doesn't work, try making a baking soda paste by mixing three parts baking soda with one part water. Apply the paste to the scorch mark, let it sit for 10-15 minutes, then gently scrub it off with a toothbrush.
Over-cleaning your cast iron pan is unnecessary and will only stand to damage your seasoning.
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.
Gently scrub the pan using mild dish soap, hot water, and a non-abrasive sponge (such as a Dobie sponge or the soft side of a Scotch-Brite sponge) or a scrub brush. Rinse it clean and then dry it completely with a dish towel.
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!
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.
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.
Black Oxide Finish for Cast Iron
It forms a durable, black magnetite coating that is RoHS and Mil Spec compliant. The process also avoids the reddish/black tint and white salt leaching problems commonly seen with conventional Hot Black Oxide.
Oil, especially canola oil (bad, unhealthy oil), should not be used. If a quick oiling (not seasoning) in between is desired, it's best to use a high temperature oil like avocado. A quick rub can do the trick, if your pan looks a bit dry. I have one pan that is about 100 years old!
Dry thoroughly right after you clean—do not let your cast iron air dry. Set on the stove over medium heat to evaporate any remaining water. Rub with a thin coat of vegetable oil (about a ½ teaspoon for a 10 inch skillet) until evenly coated and shiny. Let cool completely and store in a dry place.
We get lots of questions about this, so we thought we'd share our guide on how to properly season a cast iron pan: Wash the pan well and rinse, then dry completely. Coat the interior of the pan with a thin layer of vegetable oil, lard or shortening. Avoid using butter or a low smoke point oil such as olive oil.