Is Black Residue On Cast Iron Bad?

Chloe Meltzer
by Chloe Meltzer

Cast iron skillets are wonderful for many different types of cooking. Whether you are making cornbread, a steak, or even a simple breakfast. They add flavor and create an effect, unlike any other cooking item.

Black residue on a cast iron skillet is not bad or harmful and occurs when you cook regularly. You can remove some of the black residues with vinegar and baking soda. Season your cast iron skillet in an oven at 350 degrees Fahrenheit to prevent residue.

This black residue is merely an accumulation of charred food or burnt oil from previous meals. It could also be due to the manufacturer’s seasoning. This is common in new skillets. You should remove this and season it again if this is the case.

What is the Black Residue on My Cast Iron Skillet?

While the black residue you are noticing on your cast iron may compromise the taste of your food, it is not harmful. What causes this residue and how it forms will depend entirely on usage and the age of the cookware. With that said, it can be caused by a number of factors, including:

  • Burnt oil, especially if you use oils with a low smoke point like olive oil.
  • Charred food stuck-on from previous meals.
  • Manufacturer’s seasoning, which is relatively common among brand-new cookware. This must be removed and the skillet should be seasoned again to prevent more buildup from occurring.

Regardless of the cause or reason for black residue, it is always best to remove it. Otherwise, it will come off into your food, and could even stain your clothes. It is much easier to clean the skillet rather than attempt to wash it out of your clothes later.

Black residue is very often the result of a skillet that is unseasoned or wasn’t properly seasoned. Whereas, if all of the areas of your pan are oiled, food cannot stick to the surface and you won’t have that black layer of buildup.

By seasoning cast iron, you are essentially heating oil so that it bonds to the skillet through polymerization. This process is what prevents food from sticking and protects the surface in the process. Therefore, if you continue to cook with sticky cookware, it will start to accumulate black residue after each use.

How to Remove Black Residue from a Cast Iron Skillet

There are a few main methods to remove black residue from a cast-iron skillet.

Using Salt and Soap

This method is very popular. The best part about this method is that it is natural, and does not damage the polymerized layer (also known as the seasoning).

  • Take a 1/4 cup of salt and 1/4 cup of dishwashing soap. Place it on to the skillet.
  • Take a rag and scrub the skillet
  • Rinse the skillet off in warm water. You can use your hands to scrub it as well. Make sure all of the cleaning mixtures are removed. 
  • Use a towel to remove all moisture.
  • Now, place the clean skillet on the stove or in the oven. If you are using a stove, put it on medium heat. This should help to remove the remaining moisture. Do not skip this step as cast iron can rust easily.
  • Re-season your skillet.

Using a Self-Cleaning Oven

Although a self-cleaning oven can be used to clean the black residue off of a cast-iron skillet, you must be very careful when doing this.

  • Move all racks in your oven to the bottom.
  • Put your cast-iron skillet upside down on the top shelf.
  • Turn on your oven and wait for around four minutes. 
  • Take out your hot skillet carefully, and allow it to cool on your stove or on a metal rack.
  • After your skillet has cooled, scrub the skillet. Remove any residue or ash. 

Using Vinegar and Baking Soda

Vinegar is highly acidic which makes it great for cleaning. When you mix vinegar with baking soda, you get an extremely abrasive cleaning solution.

  • Pour a mixture of vinegar and water into your skillet.
  • Put your skillet on the stove, and allow this mixture to boil.
  • Let it boil for about a minute, then add one tablespoon of baking soda. It will begin to fizz.
  • Let it cool slightly, then use a brush to rub in the baking soda. You should see the black residue coming off easily.
  • Rinse the pan and dry it with a towel. 

If the skillet still has black residue after completing this method, you can submerge it in a mixture of water and vinegar. Let it soak for one hour, then scrub it under hot water. Repeat this a few times until there is no more black residue. Just make sure you do not leave the vinegar in your skillet overnight as it will damage it.

How to Season a Cast Iron Skillet

Since after you remove the black residue you will need to re-season your plan, you will need to know how to do so. The most important thing to remember is to season your pan without damaging it.

  • Add vegetable oil or shortening to your skillet (around one-two tablespoons).
  • Take a paper towel and rub the oil into the skillet. Do this inside and out. You want a thin coat over the entire skillet.
  • Heat up the oven to 350 degrees Farenheight, and put your skillet inside. You should put it upside down on the center rack. Place a sheet of aluminum foil under it to catch the oil.
  • Leave the skillet in the oven for an hour. Make sure it is fully cool before using it or putting it away for storage.

Why is My Cast Iron Sticky After Seasoning?

A cast iron pan that is well-seasoned will feel smooth to the touch and have almost a mirror-like appearance to it. Even though you use oil to season it, it should not feel sticky to the touch. If after seasoning, your cast iron skillet is sticky, you’ll need to determine what went wrong to cause this.

The main reasons that a cast iron pan may feel sticky after it has been seasoned are as follows:

  • You used too much oil. When you season with too much oil, it will not be cooked properly when you heat the pan. The goal is to apply a thin layer of oil to the surface when seasoning. With a thick layer, the oil also cannot absorb oxygen appropriately and turns into a congealed, sticky, hard mess.
  • You used the wrong oil. In some cases, the cast iron pan may become sticky if you use the wrong type of oil. Not all oils are suitable for high temperatures, such as olive oil which can burn easily. Instead, only use oils with a high smoke point such as canola oil, peanut oil, coconut oil, or flaxseed oil.
  • You didn’t apply enough heat. In order for the oil to develop a seasoning seal, cast iron pans must be placed in the oven to bake. Both the high heat and temperature prompt the oil to harden correctly. If it’s placed in the oven at the wrong temperature, you’ll have a sticky layer in your pan.
  • You didn’t leave it in the oven long enough. Not leaving the pan in the over for long enough can also cause stickiness. You could have the right oil and temperature, but if you don’t allow enough time for the oil to harden, you won’t get the proper seal.

How to Protect Your Skillet From Black Residue

Although black residue is not necessarily bad, it is also not ideal. Aside from seasoning your skillet, there are a few steps you can take to avoid unnecessary build-up of black residue on your cast-iron skillet moving forward.

Season After Every Single-Use

Seasoning your cast iron products is very important. However, seasoning once is not enough; it must be maintained regularly. Although time-consuming, by seasoning your cast iron skillet after every use you will avoid black residue.

Seasoning is easier than re-seasoning. This is why it is recommended to season every time you use it, instead of cleaning and re-seasoning.

  • Oil your cast-iron and heat it on the stove after every use.
  • Rub it with paper towels until it looks smooth and shiny.
  • Flaxseed oil works best.
  • You can use lard, but make sure to wipe the skillet properly so that nothing remains as lard can get rancid.

Note: While you can use virtually any oil for this, flaxseed is considered by many to be the best option. It is one of the most durable of all the cooking oils.

Don’t Worry, You Won’t Damage the Skillet

Cast-iron is extremely durable. Families hand down cast-iron pans for generations for a reason. Not only can cast-iron handle acidic sauces, but they typically remain scratch-free for years. Just remember to maintain your cast-iron regularly.

Even if you do damage it, it is repairable. If rust appears you can use steel wool to remove it. This will remove the seasoning, so you will need to re-season the entire pan. It is better to remove a small portion of rust as soon as you see it. If you do not, it will spread. When the rust spreads, you will have a lot more work on your hands to repair the entire pan.

Store it Properly

The location you choose to store your skillet in is not as important as how it is stored. You can hang it above your stove or throw it in the pantry, either way, it will be fine.
What is more important is how you store it.

Before placing your cast-iron away, it needs to be completely dry. This is because it can rust easily. Even if you think your cast-iron is dry, put a piece of tissue paper on it before putting it away. Just one drop of water might cause rust, and then you will need to re-season again.

Final Thoughts

If taken care of properly, your cast iron skillet will last you for years to come. As evident above, you shouldn’t worry about the black residue that may form on your cast iron.

While the black residue is not harmful, you will want to remove it and re-season the pan after each use. That way, you’ll prevent this buildup from transferring to your food and impacting the quality of your meals.

Related Questions

How long will a cast-iron pan or skillet last?

When taken care of properly, a cast-iron pan or skillet will last for many years. Cast-iron is known for being passed down from generation to generation.

What should I do if I see black residue on my cast-iron?

If you see black residue on your cast-iron, simply remove it, and re-season the pan. Having a bit of black residue is fine, but with more build up it can affect the taste of your food.

Is the black residue on my cast-iron pan toxic?

No, the black residue is not toxic. It is most likely a combination of burnt oil and burnt food. This is extremely easy to remove. 

Chloe Meltzer
Chloe Meltzer

Real estate agent and copywriter, originally from California. Chloe brings her real estate expertise into her writing to create effective and helpful home guides for you! When not writing or selling homes, she spends her time as a digital nomad traveling the world.

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