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Cast iron pans are known for their longevity. They can last for generations, and vintage pans work just as well as as brand-new ones. But if you're buying an old cast iron pan, there's a good chance you'll need to restore it by removing two types of buildup. First, you'll need to strip away the old layers of seasoning. Then, you'll need to remove any rust that's built up on the metal. Depending on the state of your pan, you could soak it first in lye, then vinegar. You could also try electrolysis, which eliminates old seasoning and rust in one step.

[Edit]Steps

[Edit]Using Lye to Strip Seasoning

Coat your pans with Easy-Off and seal them in bags for 24 hours. To restore cast iron pans, you can strip off the original seasoning using lye. If you are restoring just one or two pans, it is probably easiest to use an oven cleaner that sprays a lye-based foam, like Easy-Off. Spray the foam all over the pans you're restoring, seal them inside heavy-duty garbage bags, let them sit for 24 hours, then scrub with steel wool.^[1]
- Depending on your pan, it may take multiple applications and scrubbing sessions to remove all the seasoning.
Fill a bucket with lye solution and submerge the pans for faster results. If you have a lot of cast iron pans to restore—or if you just want to get the process over with more quickly—consider using a lye solution. Lye can be purchased at hardware stores, but be sure the product you purchase is pure lye.^[2] To make lye solution, use a formula of of lye crystals per of water.^[3]
- Be very, very careful with the lye—it is capable of causing bad chemical burns. Do not get it on your skin. Use heavy-duty rubber gloves and eye protection, and wear long sleeves and long pants to cover the rest of your skin.
- Always add lye to water. Never pour water over lye, which causes it to boil up.
- Lye does not affect plastic, so you can reuse old trash cans or plastic containers for this method. A bucket that holds works well for one or two pans, or try a larger size if you have many more cast iron pots to soak.
Soak the pans for 24 hours in the lye solution, then scrub them. Put on heavy-duty gloves to remove the pans from the lye. Using a mildly abrasive sponge or brush, scrub the surface of the pan to remove the seasoning that's been loosened by the lye. If, after 24 hours, there is still seasoning on the cast iron, put the pans back in the bucket for a few more hours. The seasoning will appear as dark spots on the original gunmetal gray surface of the pan.^[4]
- Lye won't harm the metal at all, so don't worry about leaving it in the solution for too long.
- Always keep the bucket covered when you're not using it.

[Edit]Removing Rust with Vinegar

Fill a 5-gallon (19 L) bucket with equal parts white vinegar and water. After you've removed old seasoning from your cast iron pans, you will then need to remove rust. Buy several jugs of cheap distilled white vinegar. Pour them into a large plastic bucket and mix with an equal amount of water.^[5]
- You can also plug your sink and fill it with vinegar and water, if you don't have a bucket on hand.
Soak the pans for up to 8 hours. Place the pans into the bucket or sink. Make sure there's enough of the vinegar-water mixture to completely cover your pans. Don't let the pans soak for more than 8 hours, since vinegar can erode and pit cast iron if it's exposed for too long.^[6]
Check the pans regularly as they soak. Each pan will need to soak for a different length of time, depending on the amount of rust that has built up. Check the pan roughly every 30 minutes by pulling it out of the water to see how much rust has dissolved. When the rust begins to flake away easily when scrubbed with a brush, take the pan out of the vinegar soak.^[7]
Scrub off any remaining flakes of rust with a sponge. Using a mildly abrasive sponge or gentle scrub brush, wash the cast iron pans to remove any last flecks of rust. Rinse with warm water.^[8]

[Edit]Using Electrolysis to Remove Seasoning and Rust

Purchase a manual car battery charger. You can buy these new at big box stores, or you can often find them at yard sales at lower prices. Double-check to make sure the label says "manual," or the charger features a switch that goes between manual and automatic.^[9]
Fill a large plastic tub with water and washing soda. Make sure your tub is big enough to hold enough water to cover the pot you're trying to clean—usually at least . Add washing soda, a laundry booster which is different than baking soda, to the water. Use roughly of laundry booster per gallon of water.^[10]
- Do this outside or in a vented garage, since it produces hydrogen gas that is potentially flammable.^[11]
- Too much washing soda can can result in excessive current and issues with overheating.
Place a piece of scrap metal into the tub. Cheap metal baking pans work well for this. Other low-cost options include rebar, used lawn mower blades, or large, flattened steel cans with the top and bottom removed. Pieces of metal with more surface area tend to be the most efficient. Make sure an inch or two of the metal sticks out of the water.^[12]
- Test with a magnet to ensure the object is steel, not aluminum, which won't work.
- You can use as many as four pieces of metal, which will speed the process along. These will need to be connected to each other by a metal wire to allow the current to pass through all of them.
Put a piece of wood over the tub and hang the pot from it. Suspend the pan from the wooden plank using a piece of wire that's threaded through the hole in the pot handle on one end and wrapped several times around the wooden plank on the other. Besides the handle, the pan should be fully submerged in the water. Make sure that the pot does not touch the pieces of metal.^[13]
- A coat hanger is an easy source of wire. Use a pair of pliers to bend it and cut it to size.
Attach the charger's black clip to the pan and the red clip to the metal plate. The clips should be attached to the parts of the pan and metal plate that are sticking out of the water. Use a stainless steel scrubber or a wire brush to remove rust or other dirt from the spots where the connector clips attach. This allows for good electrical contact and produces better results.^[14]
- If you are using multiple metal plates in your setup, the red clip only needs to be attached to one of them. The current will run through the connecting metal wire to the other plates.
Plug in your charger and let it run for several hours. Your setup is working if the water begins to foam around the cast iron pan and your charger's amp meter shows it operating at the upper end of its scale. Let the pan sit for 3 or 4 hours.^[15]
- Do not touch any part of the setup once the charger is on, to prevent electrocution.
Flip the pan, then repeat the process. Unplug the battery charger before you touch anything in the setup. As soon as it has been switched off, you can pull the pan out of the water and scrape it to see its progress. Typically the side of the pan facing the metal piece will be cleaner, so you may have to flip your pan several times between soaks.^[16]
- The pan is clean when the metal is bare and gray. Electrolysis can take can take up to 36 hours to remove rust and seasoning from a particularly dirty pan.

[Edit]Caring for Your Restored Pan

Use a mild detergent and warm water to scrub away any remaining rust. Using a slightly abrasive sponge to clean away any final flakes or rust or seasoning that remain. Steel wool or green scrub pads work well—avoid copper scouring pads, which are too abrasive.^[17]
- Do not put your pan in the dishwasher.
Dry your pans immediately. A restored pan is very susceptible to rust. Make sure you dry it completely with a towel after it has been stripped of rust and seasoning. To make sure the pan is totally dry, you could even slide it in an oven set to warm for several minutes.^[18]
Re-season your pans. Rub the entire cast iron pan down with a neutral oil, such as vegetable oil. Then, place the cast iron in the oven at . Let it bake for about an hour, then allow it to cool down for at least 45 minutes before you use it.^[19]
- Each time you use the pan to cook, make sure you wipe it down with another layer of oil. This will build up a protective coat to guard against rust.

[Edit]Warnings

Be very careful when handling liquid lye, which can burn your bare skin. Use protective measures including goggles and gloves.
If you are using electrolysis to clean your pans, do not touch any part of the setup (other than the charger) once the electricity has been turned on.
Don't use naval jelly to restore a pan. Although it can work for very small pieces of cast iron, most pans are too big to be fully submerged. Instead, it dries on the pan and becomes very hard to remove.^[20]
Also avoid sandblasting as a method to remove rust, which can permanently alter the original surface of the cast iron.^[21]