Cast Iron Pans: Why Does Oil Turn Black?

If your cast-iron pan is turning oil black, it's likely due to one of the following reasons: overheating of fats and oils, using an oil with a low smoke point, or not cleaning the pan thoroughly. To prevent this issue, ensure you use an oil with a suitable smoke point for the cooking temperature and avoid overheating. Additionally, thoroughly clean your cast-iron pan after each use, removing any burnt food particles and residue. You can use salt or a stiff brush to scrub the pan, and then apply a light coat of oil to maintain the seasoning.

The black residue is caused by carbon deposits from overheating fats and oils

If you're noticing black residue on your cast-iron pan, it's likely caused by carbon deposits from overheating fats and oils. This happens when oils with a low smoke point are used at high temperatures, causing carbonization and residue to rub off from the pores of the pan. While these carbon deposits are not harmful, they can be unappealing and affect the taste of your food.

To prevent and remove carbon residue, it's important to choose the right type of oil for cooking. Opt for oils with a higher smoke point, such as light olive oil or canola oil, instead of flaxseed oil, which has a low smoke point. Avoid overheating your pan, as this will also contribute to the formation of black residue.

Proper cleaning and maintenance of your cast-iron pan are crucial. After cooking, allow the pan to cool, then use a pan scraper or stiff brush to remove any stuck-on food residue. You can also scrub the pan with a small amount of soap if needed. Dry the pan thoroughly with a towel and place it on the stove over high heat to evaporate any remaining moisture. Finally, apply a light coat of oil to the pan's surface.

Seasoning your cast-iron pan regularly will also help reduce the formation of black residue. To season your pan, clean it thoroughly, removing any residue, and then cover the entire surface with oil, removing any excess with a paper towel. Place the pan in the oven at the highest temperature, around 500°F, for about an hour. Turn off the oven and allow the pan to cool inside. Repeat this process up to five times for a better non-stick surface.

By following these tips, you can minimize the black residue on your cast-iron pan, ensuring a cleaner and more appealing cooking experience.

The residue is not harmful, but it is unappealing

If you're finding black residue on your cast-iron pan, it's likely due to one of the following reasons:

Overheating of Fats and Oils

When oils with a low smoke point are heated at high temperatures, they carbonize and cause residue from the pores of the pan to rub off onto your food. This is not harmful, but it is unappealing. To avoid this, use an oil with a proper smoke point for your food and avoid overheating.

Burnt Food Particles

It can be challenging to clean a cast-iron skillet without removing the seasoning, so blackened bits of old food may be the cause of the residue. Thoroughly clean your pan, removing all burnt food particles.

Residue on Brand-New Skillets

Your new skillet may have been pre-seasoned to prevent rusting. This seasoning can start to flake after the first few meals you cook, especially if the oil or wax coating disintegrates at high heat.

Residue from Seasoning

The black residue may also be caused by the seasoning itself. This is common with newer cookware and will decrease as the cookware is used over time. It can also appear when cooking liquids, boiling water, using soap, or cooking acidic and alkaline foods such as beans and tomatoes.

While the black residue is not harmful, it can be unappealing and may affect the taste of your food. To remove the residue, follow these steps:

• Use salt or a stiff brush to scrub the pan. For the salt method, pour a quarter cup of salt into the pan and use a flat-edged utensil to push the salt around, discolouring it. Remove all the salt and apply a light coat of oil. For the stiff brush method, let the pan soak in water for an hour, then scrub with a small amount of soap if needed. Dry the pan and apply a light coat of oil.
• Clean off all residue using one of the methods above.
• Cover the entire surface with oil and remove the excess with a paper towel.
• Place the pan in the oven at 500°F (or as high as possible) for an hour.
• Turn off the oven and allow the pan to cool inside.
• Repeat the process up to five times if necessary.

Use an oil with a high smoke point to avoid carbonisation

When cooking with a cast-iron pan, it's important to use an oil with a high smoke point to avoid carbonisation and residue. A cooking oil's smoke point refers to the temperature at which it starts to smoke, which is before its boiling point.

Using an oil with a low smoke point will carbonise at high temperatures, and cause residue from the pores of your pan to rub off into your food. Oils with a low smoke point, such as flaxseed oil, should not be heated and are best used for salad dressings or as a garnish.

Oils with a high smoke point, on the other hand, are ideal for frying and other high-heat cooking methods. These include avocado oil, canola oil, corn oil, and peanut oil, which all have a smoke point of 400°F or higher.

When seasoning a cast-iron pan, it's best to use an oil with a high smoke point, such as grapeseed, avocado, peanut, vegetable, or canola oil. This is because you'll be heating the pan to a high temperature, and a high smoke point oil can withstand the heat without smoking and developing rancid flavours.

In addition to smoke point, other factors to consider when choosing a cooking oil include flavour profile, refined or unrefined processing, and health considerations. Some oils, like sesame oil, walnut oil, and coconut oil, have more distinct flavours that can affect the taste of your dish. Unrefined oils, like extra virgin olive oil, tend to be more nutritious but have a lower smoke point, while refined oils have a higher smoke point and longer shelf life. Finally, consider the types of healthy fats in the oil, such as monounsaturated and polyunsaturated fats, which are heart-healthy.

Clean your cast iron with salt or a stiff brush to remove the residue

To clean your cast iron pan, you can use salt or a stiff brush to remove residue. Here's how to do it:

Using Salt to Clean Your Cast Iron Pan:

• Pour a quarter cup of salt into the pan.
• Use a flat-edged kitchen utensil to push the salt around the pan.
• The salt will start to turn grey as you scrub.
• Remove all the salt from the pan to avoid corrosion.
• Apply a light coat of oil to the pan.

Using a Stiff Brush to Clean Your Cast Iron Pan:

• Let the pan soak in water for about an hour.
• Scrub the pan with a small amount of soap if needed.
• Dry the pan with a towel.
• Place the pan on the stove and heat it on high until all moisture evaporates.
• Allow the pan to cool.
• Apply a light coat of oil to the pan.

Other Tips for Cleaning and Maintaining Your Cast Iron Pan:

• Avoid using steel wool, metal scrubbers, or abrasive scrubbing pads, as these can damage the seasoning. Instead, use a pan scraper, nylon scrubbing brush, or a Lodge Chainmail Scrubber to remove stuck-on food.
• Do not put your cast iron pan in the dishwasher, as this will remove the seasoning and cause rust.
• Always dry your cast iron pan thoroughly after washing to prevent rust.
• Re-season your pan as needed by applying a thin layer of cooking oil and baking it in the oven at 450-500 degrees Fahrenheit for one hour.
• Use a light coat of oil after each use to maintain the seasoning and prevent rust.

Re-season your cast iron pan to prevent flaking

Cast iron pans are a great addition to your kitchen. They are durable and can last for generations. However, they do require some maintenance to keep them in good condition. One common issue with cast iron pans is flaking, which can occur if the layers of seasoning have not fully bonded to the metal. Here are some steps you can take to re-season your cast iron pan and prevent flaking:

• Scrub the pan: Start by scrubbing your cast iron pan with warm, soapy water and a metal scouring pad or a nylon brush. This will remove any residue, loose flakes, or stuck-on food. Rinse the pan thoroughly with water and then hand dry it completely.
• Remove rust (if necessary): If your cast iron pan has developed rust, use a Lodge Rust Eraser or fine-grade sandpaper to remove the surface rust. Make sure to remove all residual material after using the rust eraser.
• Apply a thin layer of cooking oil: Once your pan is clean and dry, apply a very thin and even layer of cooking oil to the entire surface of the pan, including the inside and outside. Oils with a high smoke point, such as vegetable oil, canola oil, or melted shortening, are recommended. Avoid using too much oil, as it may cause your pan to become sticky.
• Place the pan in the oven: Place the oiled pan upside down on the top rack of your oven. Place a baking sheet or aluminium foil on the bottom rack to catch any excess oil that may drip.
• Bake at 450-500°F for one hour: Heat your oven to 450-500 degrees Fahrenheit (230 degrees Celsius) and bake the pan for one hour. This process helps to polymerize the oil, creating a hard, protective coating on the pan.
• Allow the pan to cool: After baking, remove the pan from the oven and let it cool completely.
• Repeat the process: Depending on the condition of your pan, you may need to repeat the oiling and baking process 3 to 5 times to build up a strong layer of seasoning.
• Maintain your pan: Once your pan is seasoned, maintain it by regularly cooking with oil. Each time you cook with oil, you add another layer of seasoning. Avoid using excessive heat or cooking acidic foods, as these can break down the seasoning.

By following these steps, you can re-season your cast iron pan and prevent flaking. With proper care and maintenance, your cast iron pan will provide you with many years of delicious cooking!

Frequently asked questions