The Mystery Of The Stained Iron Pan: Unraveling The Science Behind The Marks

Stains on iron pans are usually caused by the overheating of fats and oils. Using an oil with a low smoke point will carbonize at high temperatures and cause residue from the pores of the pan to rub off onto food. This residue is not harmful but can be unsightly. Stains can also be caused by food particles that have burnt and stuck to the surface of the pan. To avoid staining, it is recommended to always use oil or cooking spray when cooking and to avoid preheating the pan without oil or water.

Stains from burnt food

Burnt-on food is a common problem for even the most diligent of cooks, but it's usually possible to remove the stains and restore your pan. Here are some methods to try:

The Deglazing Technique

First, remove as much burnt food and debris from the pan as possible. Then, put the pan back on the stove and heat until a droplet of water sizzles on the surface. Add a cup of water or a mixture of half water and half white vinegar to the pan and boil. As the liquid simmers, use a spatula or scraper to deglaze the bottom of the pan, loosening bits of burnt food. Pour the liquid into the sink and sprinkle the bottom of the pan with baking soda. Let the pan cool, then use a wet scouring sponge or nylon brush to scrub the pot bottom vigorously. Finally, wash and dry the pan as normal.

The Baking Soda and Water Method

Remove as much food and debris from the pan as possible. Make a paste of three parts baking soda to one part water—you'll need enough to cover the scorched portion of the pan. Alternatively, cover the bottom of the pan with a thin layer of warm water, then add enough baking soda to create a paste. Let the mixture sit for a few hours or overnight, then add more baking soda and scrub with a nylon brush or scouring sponge. If you don't want to wait, add a quarter to a half cup of water to thin the paste, then put the pan on the stove and bring to a boil. Remove from the heat and let the pan cool before wiping or scrubbing to remove the scorched bits.

The Baking Soda and Vinegar Method

Remove as much food and debris from the pan as possible. Add enough white vinegar to cover the bottom of the pan with at least half an inch of liquid and boil in the pan. Remove from the heat and add a cup of baking soda—this will cause a fizzing reaction, so it's best to do this in the sink. Set the pot aside and wait until the fizzing stops. Discard the liquid and scrub the pan with a nylon brush or scouring sponge, adding more baking soda if necessary. Rinse and dry the pan.

The Baking Soda and Lemon Method

Remove as much food and debris from the pan as possible. Keep a thin layer of water in the pan and sprinkle the bottom liberally with baking soda. Cut a lemon in half and use the flesh to scour the pan—the combination of the acidic lemon juice and alkaline baking soda will fizz slightly. If your pan has a copper bottom that has become blackened or tarnished, turn the pot upside down and use this method to remove the stains and restore the shine.

The Soaking Method

Soaking a burnt pot in hot water can help loosen burnt-on food. For extra cleaning power, add common household items like baking soda, vinegar, lemons, Alka-Seltzer, or dishwasher tablets. For example, you can add a few drops of dish soap to hot water, or combine baking soda and vinegar to create a fizzing reaction that breaks down burnt food. You can also use a ball of aluminium foil or a dryer sheet to scrub away burnt-on food. However, abrasive cleaners and scouring supplies should never be used on non-stick surfaces, and cast-iron pots and pans shouldn't be exposed to prolonged soaking or harsh scrubbers.

Stains from rusting

To prevent rust stains, always dry your iron pan over medium-low heat on the stove after washing it. This will help to evaporate any lingering water that might not be visible to the naked eye. Even if you dry your pan with a towel, there may still be some remaining moisture because iron is porous.

If your iron pan does develop rust stains, there are several methods you can use to remove them:

• For minor surface rust, rub about 1/3 cup of kosher salt into the surface of the pan with a scouring pad or kitchen towel until the spots of rust are removed.
• For more serious cases of rust, start by soaking your pan in vinegar. Mix equal parts water and distilled white vinegar in a container that will fit your pan, ensuring that the entire pan, including the handle, is submerged in the mixture. Check the pan every 15 minutes and remove it from the solution once the rust easily flakes away. This can take anywhere from one to eight hours. Be sure to frequently check on your pan, as you don't want the vinegar solution to penetrate and start eating away at the original cast surface of the pan.
• Using something lightly abrasive, such as a stiff brush or a scouring pad, scrub away the rust under cold water. The cold temperature helps prevent the rust from reforming quickly.
• For very severe rust, you may need to immerse your pan in a vinegar bath. Immerse your pan in a solution of equal parts white vinegar and water for about an hour. Then, scrub any remaining rust off with something abrasive, such as a scouring pad or steel wool.

Once you have removed the rust stains, dry your pan thoroughly with a paper towel or lint-free cloth. You can then coat it with a thin layer of cooking oil, such as vegetable oil, to protect it from rusting while it's not in use.

Stains from seasoning

The black stains could also be due to burnt food particles, especially if your pan is not well-seasoned. Burnt-on food can be removed by simmering some water in the pan for 3-5 minutes and then using a pan scraper. You can also try using a nylon brush or nonscratch pad, or steel wool or a metal scrubber if you are preparing to re-season the pan. Make sure to dry the pan thoroughly and add a layer of oil afterward.

If your pan is new, it may have been pre-seasoned to keep it from rusting in the store. This seasoning can start to flake after the first few meals you cook, as the oil or wax coating will disintegrate with high heat. To fix this, clean off all residue, cover the entire surface with oil, and remove the excess with a paper towel. Then, 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 this process up to five times if needed.

If your pan is sticky, this is a sign of excess oil buildup. To remedy this, place the pan upside down on the top rack of the oven and bake at 450-500 degrees F for one hour. Allow it to cool, and repeat if necessary.

Stains from overheating fats and oils

To prevent stains from overheating fats and oils, it is important to use an oil with a high smoke point suitable for the cooking temperature. Additionally, avoid overheating your pan, as this can cause the oil to break down and leave residue.

If you do end up with stains from overheating fats and oils, there are several methods to clean and re-season your cast-iron pan:

• 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, soak the pan in water for an hour, scrub with a small amount of soap if needed, dry with a towel, and set on high heat to evaporate all moisture. Then, allow the pan to cool and apply a light coat of oil.
• Clean off all residue using the methods above, then 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 this process up to five times if needed.
• Use a pan scraper to remove stuck-on food residue. If the problem persists, simmer some water in the pan for 3-5 minutes, then use the scraper again. Dry the pan thoroughly and add a layer of oil.

Remember, cast-iron pans are very durable, so don't worry if you make a mistake while cleaning or seasoning. With proper care and maintenance, your pan will develop a black seasoning that acts as a good non-stick surface over time.

Stains from baked-on food

Boiling Water and Baking Soda Method:

This method is recommended by Lodge Cast Iron for removing stubborn baked-on food from enameled cast iron.

• Boil 2 cups of water and 4 tablespoons of baking soda for a few minutes.
• Use a pan scraper to loosen the food.
• Clean the pan with soap and a scrub brush.

Lodge Enamel Cleaner:

Lodge, a reputable cast-iron cookware manufacturer, suggests using their enamel cleaner or another ceramic cleaner to remove slight stains from enameled cast iron.

• Clean your enameled cast iron as usual by hand-washing it with warm soapy water and a nylon scrub brush.
• Rub the cookware's surface with a damp cloth and Lodge Enamel Cleaner or a similar product, following the directions on the bottle.

Bleach Soak:

While bleach is a controversial choice for cleaning cookware, some people swear by it for removing tough stains from enameled cast iron.

• Soak the interior of the cookware for 2-3 hours with a mixture of 3 tablespoons of household bleach per quart of water.
• Rinse thoroughly and ensure no bleach residue remains before using the cookware again.

Salt and Oil Scrub:

This method can be used for cast iron that is not enameled.

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

Water and Soap Soak:

For cast iron without enamel, you can try soaking the pan in water and then scrubbing it with a stiff brush.

• Let the pan soak in water for about an hour.
• Scrub with a small amount of soap if necessary.
• Dry with a towel and place on high heat over the stove to evaporate any remaining moisture.
• Allow the pan to cool before applying a light coat of oil.

Remember to always hand-wash your cast iron cookware and avoid using citrus juices or citrus-based cleaners, including some dishwasher detergents, as they can dull the exterior gloss. Additionally, avoid preheating your enameled cast iron without oil or water, as this can scorch your pan and damage its finish.

Frequently asked questions