How to restore rusty cast-iron pans (clean, reseason & save them)

If you use cast-iron pans regularly, you know how important a good seasoning layer is. But what if your pan is rusty, sticky or completely neglected?

Don’t throw it away. With a bit of cleaning, oil and heat, you can fully restore any cast-iron pan and make it cook like new again. Here’s exactly how we do it.

Here’s how we tackled it ourselves. We got a very nice antique cast-iron poffertjes pan that needed some love. For all you non-Dutch viewers, a poffertjes pan is a thick, cast-iron plate with 5 cm-diameter dimples. In those dimples, we cook small puffy pancakes called “poffertjes”. Now you know.

The dark brown layer on this poffertjes pan was no longer really a hard coating but a thick layer of dirty grease. Although the fat protected the pan from rust, it was not really sanitary to cook in it.

We decided to make the pan completely bare and season it with a nice new coating. While we were at it, we grabbed the rest of our cast-iron pans that could use some extra care. Some pans had a thin layer of rust, and others were starting to look a little bare. It was high time to do something about it.

How to remove old seasoning from cast-iron

Old seasoning can easily be removed with a steel sponge. If the layer is not too thick, you will have a bare pan in a few minutes. If the coating is still hard, you can choose to leave it on or spend a few extra minutes on it.

Rust removal from cast iron

If the cast iron is rusted or there is a thick layer of lousy seasoning on the pan, you must devise a better plan. You can put the cast iron in a bath with vinegar to soften the seasoning and rust. The problem is that you must pay attention and rinse off the vinegar immediately after you pass through the rust layer. The vinegar can affect the cast iron, worsening the problem.

We prefer to control the process ourselves and put in some elbow grease. First, we remove the first layers of coating, old oil, dirt, and rust with a brass wire brush. A brass wire brush is hard enough to remove the baked-on mess without damaging the harder cast iron. It may help to heat the pan slightly so the dirt and grease soften.

Then we use sandpaper to completely bare the cast iron. It takes some effort, but it’s all worth it. If the pan is completely free of rust and you only see a grey metal layer, rinse it thoroughly under running water. Then dry it well and heat the pan until all the moisture is gone. If you wait too long with this, you will see rust forming within the hour, and you can start over.

How to season cast iron?

We have always used vegetable oil to coat our cast-iron pans, preferably one with a high smoke point. The higher the temperature at which you season the cast iron, the harder the coating remains. So, if you use your cast-iron skillets to sear a steak occasionally, you want a layer that also protects at higher temperatures.

You sometimes hear that you build up flavour in a cast-iron pan every time you use it. If that’s the case, you know the seasoning isn’t hard enough, so the fat from the dish ends up in the coating. This fat will melt the next time you use the pan. That old fat then gives its flavour to the recipe you are preparing at that moment. You might like this idea, but it makes us a little nauseous.

We have found that clarified butter, or ghee, works very well for seasoning cast iron. Clarified butter is butter whose solid components are separated from the fats. That way, you only have pure fat left. That fat has a smoke point of about 250°C (480F). A lot higher than regular butter or the vegetable oils named earlier. This gives you a nice, hard coating that can withstand higher temperatures. You can safely bake pies in these pans without tasting last week’s steak.

Using vegetable oil with a lower smoke point also has an advantage. Because most ovens do not get hotter than 250°C (480F), you cannot season cast-iron in them with oils with a higher smoke point. We season our cast-iron cookware outside in the smoker because it can get much hotter.

If you have greased the cast iron, you must remove most of this oil. Use a paper towel to wipe away the oil until only a thin, barely visible layer of fat remains. The thinner, the better. Properly seasoning cast iron is a matter of applying several thin layers.

If you heat this thin layer of oil above the smoke point, a chemical reaction called polymerisation occurs. If you heat oil above its smoking point, the fat will decompose. This creates new connections that attach themselves to the underlying material. The thinner the layer, the faster this happens and the harder that layer becomes. So, applying several thin layers rather than one thick layer is better, and it never hardens completely.

At what temperature do you season cast iron

As we said, each type of oil or fat has its smoke point. For most oils or fats, this is between 160 and 200°C (320 to 392F). First, find the smoke point of the oil you are using, then set your oven to a temperature about 20 degrees higher. Not much higher because after the smoke point comes the burning point, and then all your hard work is for nothing. Fat or oil that burns turns into ash and can be wiped off or taint the coating.

Our clarified butter has a smoke point of 250°C (480F), so we set the smoker to 270°C (518F) and waited until it reached the right temperature. At lower temperatures, some smoke can come from the charcoal, which settles onto the still-soft layer of oil, making it dirty.

We placed the pans upside down on the grill so that any fat that had been applied too thickly could run out. We left the pans like this for 20 to 30 minutes. We warned the neighbours that it could start to smell a bit, so they could close the windows and bring in the clean laundry. A good relationship with the neighbours is worth a lot.

That stinking smoke is also why we no longer season our cast iron indoors. One pan was still okay, but with several pans cooking simultaneously, you had that foul-smelling smoke in the house for days. That smoke is also poisonous, so you know.

How many layers of seasoning do we apply

We apply at least six layers of seasoning to bare cast iron. The whole process, including cleaning, can take up to 3 hours. It’s an excellent job for a free afternoon. Maybe you can cook something delicious on another grill to hide the bad smells. Make some more to give to your neighbours sitting in that foul air that same afternoon.

With the skillets that were in better shape, we paid close attention to when the layer was nice and even, black and had a slight shine. Then you know that you are done. An extra layer never hurts.

You’re done when your pans are black, and there is no more soft fat. All you have to do now is use the pan a lot. The only thing to remember is that if you prepare fatty dishes, the coating remains intact. The coating will be affected if you prepare more acidic dishes, such as tomatoes. Don’t worry that the coating will disappear immediately; it never hurts to add an extra layer of seasoning to the pan following the above steps.

It’s also a good idea to grease the pan a little when you store it, but only if you use the pan regularly. The fat protects the pan from rust, but can become rancid if left in place for too long. The fat does not create a hard coating because you do not heat the oil above its smoking point.

If you season your old cast-iron pans and skillets this weekend, let us know in the comments below. Or better, take a photo and post it on Instagram. Tag @bbq.heroes so we can see what you’ve done.