Black Residue On Cast Iron Skillet. Is It Harmful?

CRYSTAL H.  | ,   |   Updated
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Sometimes cooking with a cast iron pan, do you get black specks appearing in your food? Or… a dark residue on the cloth when wiping the pan after cleaning. What’s that black stuff coming off my pan and should I be worried? Here’s what to know and how to avoid getting that black residue from your pan.

Cooking with cast iron, black specks on food

Is black residue on cast iron skillet harmful?

That black residue on your cast iron skillet is usually carbon deposits, which are not harmful. These deposits causing that black stuff coming off your pan into your food or onto your cleaning cloth are from the overheating of oil or fats, or bits of burnt-on food.

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The blackened carbon collects in the pores of the pan and black bits become disturbed during the cooking process. Hence why you get these black specks in your food. They may harm the appeal of your food but the small amount of carbon residue is not considered harmful in itself.

So…It may not be harmful, but having black specks in your food is probably something you don’t want. Let’s look at how you can prevent this black residue problem… 

What’s this black stuff!

What’s the black stuff coming off cast iron skillet?

The black residue looks like this:

  • Dark flecks on the food that wasn’t part of the ingredients
  • Dark flecks that taint the flavor and appeal of your cooking
  • Dark stain that messes up your clean towel when wiping the skillet.
  • Black flecks on your eggs that isn’t the pepper. (The whites of eggs make them horribly noticeable.)
  • Black flecks showing up after you’ve used the metal spatula because it disturbed deposits nestled in the pores of the pan’s surface.

Why do I have This black Stuff

The black residue from the pan that’s showing up in your food has three possible sources or reasons why the pan has this black residue…

  1. Overheated oil, layers of oil or fat that carbonized
  2. Bits of food particles that stuck and charred with previous use
  3. Residue from the manufacturer’s seasoning or coating they applied to stop the pan from rusting (new skillets only)

#1. Overheating of oils and fats

If you are using an oil that has a low smoke point then it’ll carbonize at high temperatures and result in a black residue that subsequently rubs off onto your food.

#2. Charred food particles

Carbon residue can form from bits of food left stuck and burned to the bottom of the pan. As you continue to use and heat the pan’s surface, these deposits will char. The burnt on carbon deposits aren’t always removed with a simple cleaning.

#3. Black residue from brand new skillets

The cast iron skillet seasoning could be flaking off. Many new cast iron pans come with a layer of oil or wax coating to prevent them rusting before being sold and you might find this intended cast iron seasoning coming off.

The cast iron skillet seasoning could be flaking off. Many new cast iron pans come with a layer of oil or wax coating to prevent them rusting before being sold and you might find this intended cast iron seasoning coming off.

As you begin to use the cast iron, the pre-seasoning of a layer of oil or wax will burn and leave behind charred carbon residue that resembles a black coating.

This black coating is intended as a temporary fix and may not be the best for heat tolerance. The solution is to clean the black stuff off and then do a good job of re-seasoning the skillet.

Other causes of stains from cast iron pans

Also, what can cause flecks or residue is rusting of the pan causing iron micro-particles to be released. You might see this as brown spots on your cast iron skillet. Should you get rid of rusty pans?

Brown spots cast iron

Your cast iron has brown spots? The brown spots or staining are micro bits of cast iron flaking from the pan’s surface — don’t worry, your pan is not defective. Acidic foods, such as tomatoes, will cause this if the pan is not sealed properly. A good clean and seasoning will fix it.

The brown residue is iron and the problem is surface rusting, which can be fixed. Unless you have been advised by your medical practitioner to avoid extra iron intake. Most people will benefit from the added iron in the diet.

How to prevent the black residue

With proper cooking techniques, cleaning, and seasoning you will reduce the build-up of this carbon residue and have no more black coming off your pan affecting your cooking.

Proper techniques in cooking will help you avoid black residue forming in the cookware. This amounts to selecting a cooking oil or fat with a high enough smoke point. Certain oils, such as virgin olive oil, have low smoke points. If these are overheated they will burn and blacken. You’ll know when it happens as you will see smoke coming off the oil as it is burning.

It also means using a seasoned skillet, which reduces the likelihood of food sticking and charred deposits forming in the pores of the pan.

If your problem is caused by charred food from previous cooking, simply make sure to better clean your pan in warm water with some detergent, giving it a good scrub with a nylon brush, after each use.

In terms of black residue from brand new skillets, try stripping off the seasoning and re-season the pan. Taking the time to prepare and season the pan should remove any low-quality sealants or residue. 

How to clean black residue off cast iron skillet

How do I get the black residue off my cast iron skillet? There are a few useful methods of effectively cleaning cast iron and stripping the black layer of residue. Below are two techniques. One uses salt, the other involves a stiff brush.

Cleaning cast iron skillets with salt

Salt is not only a popular seasoning but also a powerful abrasive, a pantry staple, and cheap. You could also use baking soda in much the same way.

Here’s how to get residue off cast iron skillets using the salt method…

  1. Pour a good amount of salt, into the pan. A coarse grain like Kosher salt will work best. Aim for a quarter of a cup of salt or so.
  2. Use a kitchen utensil with a flat edge (try a wooden spatula) to scrape the salt around the surface of the pan. You might need to spend a bit more time scrubbing those extra stuck bits.
  3. As you scrub, you’ll notice the salt discoloring. Wipe the salt from the pan with a cloth or paper towel, ensuring to remove all the grains. Moisture in the air mixed with salt on the pan will be highly corrosive.
  4. Give it a good rinsing with hot water if you have the opportunity but using salt is an excellent way to clean the pan without needing to wet it.
  5. Coat the pan in a light coat of oil and burn it off in a hot oven or on the stovetop to season the pan before storing it.

Cleaning cast iron pans with a stiff brush

If your residue is stuck on, you may want to grab a stiff brush. It needs to be something stiff enough to remove the black residue, but not so tough as to strip any seasoning.

  1. Soak your pan in warm water for an hour or so.
  2. Scrub the pan thoroughly to remove all stuck-on residue.
  3. Use a small amount of detergent if necessary.
  4. Dry the pan completely with a towel.
  5. Place the pan on a burner set to high heat. Allow the pan to sit on the burner at medium heat until all traces of moisture have evaporated. 
  6. Allow the pan to cool.
  7. Coat the pan in a light coat of oil before storing. 

If your pan has a lot of burnt-on or caked-on residue, it may be difficult to clean off. In a dire situation, you may want to simply start over and re-season the pan entirely. This will remove anything stuck to the surface and allow you to start a new coat of oil. 

For more options, see my article on cleaning cast iron cookware.

Sealing a cast iron skillet — The Seasoning process

Sealing a cast iron skillet means building up a decent layer of seasoning. Not only will it turn it into a non-stick surface, but will stop rusting and help deter black residue on the cooking surface.

Here are two ways to keeping your cast iron seasoned.

How to re-season a cast iron pan

  1. Work off any large burnt-on bits with a stiff brush or sponge.
  2. Use steel wool to scrub down every surface of the pan, entirely removing any stuck particles.
  3. If there is a thin layer of rust formed over the surface of the pan, remove it by rubbing the entire pan down with oil and then wiping away the excess. 
  4. Cover the entire surface of the pan with oil again. Remove most of it with a paper towel, leaving only a thin layer of oil. 
  5. Place the pan in the oven at 500 °F or as high a temperature as possible with your oven for about one hour.
  6. Turn off the oven and allow the pan to cool while in the oven.
  7. Repeat up to 5 times, if needed, to get the best finish on the surface.

An easy 1-step way to keep your cast iron skillet seasoned

Lodge have this seasoning spray that you simply apply on your cast iron skillet after each clean. It’s made in the US and is 100% canola oil – no additives, no propellants.

To keep cast iron cookware in top condition, seasoning is important. This product by US company, Lodge, will make that a breeze…

Lodge Canola Oil 8 Ounce Seasoning Spray

Available at Amazon

In closing

Cooking with cast iron has its benefits. So, in terms of “is black residue on cast iron skillet harmful?” there’s no need for over-concern. Having black residue on cast iron skillet might harm the appeal of your food, but the good news is that it is not harmful to you and it is preventable.

By not overheating the oils and fats when cooking and by taking proper care of your pan, you can rid yourself of this problem.

Cast iron pans are fairly robust but as I explained in my non-stick cookware use, care, and storage guide, knowing how to get the best out of your cookware will give you the most satisfaction in their performance for longer.  


Info sources Cooking With Cast Iron |

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