Black Residue on Cast Iron Skillet…Is it Harmful?

My work is reader-supported; if you buy through my links, I may earn affiliate commission, at no extra cost to you. Full disclosure here.

Sometimes when you’re 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 cast iron pan and should I be worried? Here’s what to know and how to avoid getting black residue on your cast iron pan.

black residue on cast iron skillet, cast iron skillet brown residue
Cast iron skillet brown spots or black residue – is it harmful?

Is black residue on cast iron skillet harmful?

That black residue on your cast iron skillet is usually just carbon deposits. It is not harmful. The carbon deposits causing that black stuff coming off your cast iron pan into your food or cleaning cloth form due to the overheating of oil or fats, or bits of burnt food.

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 cast iron black residue from occurring… 

What’s this black stuff!

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

What are the specks when I wipe my cast iron skillet?

After cooking in a cast-iron skillet, you notice black residue as…

  • The dark flecks appearing on your food that weren’t part of the ingredients while you were cooking.
  • The dark flecks that appeared and tainted the flavor and appeal of your cooking.
  • The dark stain that messed up your clean towel when wiping the skillet.
  • The black flecks on your eggs that aren’t the pepper. The whites of eggs make them highly noticeable.
  • The black flecks you see after you’ve used metal utensils on your skillet, which disturb the carbon deposits nestled in the pores of the pan’s surface.

Why does my cast iron pan have black residue?

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

  1. Overheated 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 cast-iron surface, these deposits will char. The burnt on carbon deposits aren’t always removed with a simple cleaning.

cast iron black residue, black residue on cast iron skillet that has formed from charred meat
Cast iron black residue forms during the cooking process

See also: My No.1 Way To Clean A Pot With Burnt On Food

#3. Black residue from brand new skillets

The black residue might be the cast iron skillet seasoning 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.

These coatings are intended as a temporary fix and aren’t necessarily the best for heat tolerance. 

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 from the cast iron are micro bits of cast iron flaking from the pan’s surface — don’t worry, your pan is not defective. It just means it needs sealing. A good clean and seasoning will fix it. I cover how to do this below.

The brown residue is iron and the problem is surface rusting, which can be fixed. Iron intake is not overly concerning, 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 cast iron cookware. This amounts to selecting the right oil or fat for your cooking purpose and avoid overheating it with temperatures that will cause it to burn. You’ll know when this occurs as you will see smoke coming off the oil as it is burning. It also means using a seasoned cast iron 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 after each use.

In terms of black residue from brand new skillets, try stripping off the seasoning and reseason 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 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 can use the roughness of regular table salt to get a good scrub on your pan.

Here’s how to clean cast iron skillets using the salt method…

  1. Pour a good amount of salt into the pan. Aim for a quarter cup 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. Coat the pan in a light coat of oil before storing it.

A third point…salt is excellent as a way to clean the pan without needing to wet and dry 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 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

Sealing a cast iron skillet, otherwise known as seasoning, will help prevent black residue from forming on the cooking surface as well as stop the pan from rusting. Here are two ways to keeping your cast iron seasoned. One is a simple approach.

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 |

Share on: