I have a generation-old cast-iron skillet I use to fry pretty much everything, thanks to its unmatchable heat conduction. This skillet requires occasional seasoning and careful handling to stay spick and span. However, it’s not always been the same; once a black coating started coming off my skillet, and anything I’d cook would come out brownish.
Since I wasn’t sure what’s that coating (I am talking about some ten years back), I asked around and realized this is a usual phenomenon. Every cast-iron skillet/pan’s black coating gets damaged with time, making its insides dusty.
If you’re facing the same problem and unsure why the black coating is coming off your cast-iron skillet, let me help you.
Cast-Iron cookware is grayish-silver when it’s not polished or rusted. Manufacturers build a polymerized fat layer (mostly black) on the bare cast-iron surface to prevent rust, which gets thicker with each use. This black coating works like a non-stick surface, but it requires some maintenance to stay the same because otherwise, the black residue leaches into your food.
Fixing this loose black coating is possible, and this guide is all about it; read on to preserve your cast-iron cookware and use it however you want.
What is that Black Residue Coming Off Your Cast-Iron Skillet?
Bare cast-iron gets rusted within minutes of contact with water and moisture; hence, a polymerized fat is later transferred to its surface. This fat layer gets scratched with regular usage and temperature changes, eventually affecting your food’s color and taste.
Here are three types of black residue you might see coming off your cast-iron skillet:
Cast-iron is manufactured by mixing Iron alloy with Carbon and Silicone; pure Iron cookware is heavy and not-so-practical for home cooks. Regular use (and sometimes abuse) loosens Carbon deposits, and they start leaching into your food. Although these Carbon traces aren’t toxic, they ruin your food’s look.
Seasoned Layer/Burnt Fats
Most cast-iron cookware comes pre-seasoned from the factories because it gets rusted otherwise.
But one problem with industrial seasoning is that you don’t know which fats they used on your skillet. It could be a low smoke point oil that cannot survive regular temperature changes.
Moreover, using different heat sources and temperatures impacts this polymerized layer’s strength, making it flaky over time.
If you notice hard flakes coming off your cast-iron cookware, it’s the seasoned layer, and you need to remove it ASAP (more on this later).
If your cast-iron skillet’s seasoned layer seems unharmed, but there’s still black residue on your food, charred food is the culprit. When we regularly use a skillet, some food and fat residue stick to its surface, piling up with time.
Lard, shortening, and vegetable oils can also accumulate on a cast-iron surface, eventually disturbing your cooking experience. You need a smooth, non-stick cast-iron surface, and that requires some effort.
Why does the Black Coating come off Cast-Iron Cookware?
Now that we know what’s that black residue coming off your cast-iron skillet, let’s understand why that happens. Are you doing something wrong, or there’s some flaw in your cookware?
Here are the main reasons you see the black coating coming off your cast-iron skillet:
Brittle Utensils (Very Rarely)
Sure, cast-iron cookware is tough as nails and doesn’t require any babying to perform well, but that doesn’t mean you start using sharp utensils above the seasoned layer. Using metal turners, spatulas, and ladles doesn’t harm the cookware, but they scratch some particles of the black patina layer.
Once these brittle utensils weaken some part of the coating, it doesn’t stop there. Every time a brittle spoon moves over the seasoned layer, it escalates the flaking process, eventually eroding the entire surface.
If you prefer brittle utensils with cast-iron cookware, make re-seasoning a habit, and you’re good. No need to throw your favorite utensils back in the closet; some care will suffice.
When you put a super-hot skillet directly under tap water, you’re in for some big damage. Metal cookware expands when heated, and it needs time to contract. If you stimulate the contracting process by putting it in water, the metal surface gets warped, and the seasoning gets weak.
Let your skillet cool down at room temperature before washing, and its black patina layer will last longer, plus it won’t lose balance.
Machines make our lives easier, but some things are better off with traditional ways; seasoned cast-iron cookware is one of them. Dishwashers don’t damage bare cast-iron, but they can scratch the patina layer.
If you prefer loading everything in the dishwasher, take out your favorite cast-iron skillet and wash it manually.
Firstly, you only need water to remove food residue from the cast-iron skillet, so no dishwasher detergent is needed. Secondly, other utensils and tools stuffed in the dishwasher can dent the seasoned layer, rendering it useless; some care will go a long way.
After you wash a cast-iron skillet, quickly absorb the moisture from its surface with a kitchen towel to protect the seasoned layer. Moisture eats away the metallic/seasoned surface; you should avoid that.
Hang or stack your seasoned cast-iron skillet after completely drying it to ensure there’s no moisture/lose gunk left.
How to Remove Black Residue from A Cast-Iron Skillet?
If you see the infamous black residue in your cast-iron skillet, fret not because dealing with it is easy. Follow any of these three cleaning methods to remove the black residue from your cast-iron skillet:
- Salt & Dishsoap
Salt is a harmless abrasive agent, which doesn’t scratch your cookware’s surface during the cleaning process.
Mix a quarter cup Kosher/Sea salt with dish soap and pour this mixture on your skillet. Use a rag/scrubbing pad to rub this mixture on the skillet and remove the grimey surface.
This salt-soap mixture will remove all charred food, burnt oils, and carbon deposits from the skillet without damaging the seasoned layer.
Once the black residue is off, dry your skillet and re-season it with a high smoke point oil to regain the non-stick cooking surface.
- Self-cleaning Oven
If your skillet’s seasoned layer is coming out in flakes, it’s time to get rid of it. You can easily remove the seasoned layer with a self-cleaning oven and re-season it to enjoy non-stick cooking.
Place your cast-iron skillet in the self-cleaning oven, face down, and set the temperature to 800F; the temperature is usually required to complete the oven’s cleaning cycle.
This extreme high heat will melt the charred food and fats, leaving you with a pristine skillet. Once the seasoned layer is off, re-season it and say goodbye to the black residue (for some time, of course).
- Baking Powder & Vinegar
Baking soda and vinegar make the ideal cleaning solution for your cookware, cast-iron included.
Mix some white vinegar in water and boil this solution in your cast-iron skillet. Once it boils, add a tablespoon of baking soda, and let the mixture sizzle for a while.
Turn off the heat and leave the skillet to cool at room temperature. Once it’s safe to touch, use a scouring pad to remove the cleaning solution and black flakes from the skillet.
How to Keep the Black Coating from Coming Off?
Once you have removed the problematic black coating from your skillet and developed a new one, follow these care instructions to enjoy it for a longer duration:
The seasoned oil film works like a non-stick cooking surface above your cast-iron cookware, don’t let go of it. Add a high smoke point oil or lard to your skillet and bake it in the oven for 1 hour; heat will polymerize these fats and leave your skillet with a thin plastic-like film.
After the initial seasoning is done, don’t forget to maintain it. Once a week, coat your skillet in some fats before storing/stacking it to prevent scratches and bulges.
If the black residue is back, clean it again and re-season the skillet to ease your cooking experience.
You aren’t supposed to wash cast-iron skillets daily or scrub them to death; gentle rinsing is enough. Every time you fry or cook something in the skillet, run it under tap water and wipe it with a kitchen towel; that’s it—no need to use soap, brittle sponges, or hot water to clean a cast-iron skillet.
Another tip is never to leave a cast-iron skillet moist; always towel dry it to prevent rust. If you stack cast-iron cookware, place tissues/paper towels between each item to protect their patina layers.
Is that loose/flaky black coating harmful? Fortunately not. Regularly used cast-iron cookware is supposed to build a patina layer, which thickens with time. If something brittle scratches this patina, the flakes start coming off, leaving your food in a weird color. However, these flakes aren’t toxic; they’re either charred food traces or burnt fats. Clean your skillet thoroughly and re-do the seasoned layer to prevent this problem in the future.
Do we have to wash a cast-iron skillet after every use? Not necessary; professional chefs prefer rinsing and wiping their skillets to maintain the patina layer. You can also rinse and wipe your cast-iron skillet after every use. However, if food burns inside your cast-iron skillet, clean it with a soft brush and a mild dish soap to keep the patina layer intact.
Cast-iron cookware doesn’t add to your workload if you follow the important care instructions. If your skillet’s black coating is coming off, take it off and season your skillet to enjoy an impeccable cooking experience. This black coating isn’t toxic, so don’t worry if you see brownish particles in your food, do some cleaning, and your skillet will be good again.