Here’s What Really Happens When You Put Cast Iron in the Dishwasher

If you're one of the lucky ones, you inherited your cast-iron skillet from your grandmother, who had it for decades. Perfectly seasoned and naturally nonstick, it can handle almost anything—sunny side-up eggs, sautéed vegetables, pan-seared steak, and many other delicious dishes. While cast iron can last for generations, it still requires proper care.

Cast iron differs from other cookware because you shouldn't clean it with dish soap or detergent; in fact, those products can damage the seasoning. Using soap on cast iron is a bad idea, but putting it in the dishwasher is even worse. If you've recently made that mistake, don't panic. We spoke with experts to explain exactly what happens when you run cast iron through a dishwasher cycle and how to repair it.

What Happens When Cast Iron Goes in the Dishwasher

What makes cast-iron cookware unique is that it often comes pre-seasoned. Manufacturers create the finish by baking a layer of oil onto the surface to form a natural, nonstick coating, says Kris Stubblefield, chef at Lodge Cast Iron. And the longer you cook with it, the more seasoned it becomes.

Prolonged exposure to water, soap, and detergents can strip away that seasoning layer you have built up over the years of cooking. The seasoning protects the metal from oxygen, and when it breaks down, rapid oxidation—also known as rusting—occurs.

When cast iron goes through a dishwasher cycle, the detergent strips the seasoning, breaks down the oils that preserve it, and damages the skillet, causing what experts call "flash rust." To repair and maintain the polymerization, nonstick surface of cast iron, you must repeatedly use and oil it with a high-smoke-point oil, according to Seth Affoumado, founder of The Skillet Doctor.

Cast iron performs best and can last for generations when you hand-wash it with only warm water—no soap—dry it completely, and lightly oil it after each use, Stubblefield says.

Signs Your Cast Iron Has Been Damaged

While one dishwashing cycle likely won't make or break your cast iron, here are a few signs that indicate it has been damaged and needs extra care.

"The most common sign is visible rust, which can appear if cast iron has been exposed to water or moisture," Stubblefield explains. "You may also notice that the seasoning has worn away. If rust is visible on the surface, it’s a clear sign the cookware needs to be cleaned and restored."

If the cooking surface looks blotchy or uneven, strip and re-season the skillet, Affoumado says. In addition to rust or uneven seasoning, a cast-iron pan is damaged if it doesn't sit flat or develops cracks.

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Steps to Restore Your Cast Iron

First, don't panic. Accidents happen, whether you're new to owning a cast-iron skillet or a houseguest kindly helped with doing the dishes without knowing that you should never put a cast-iron skillet in the dishwasher. Regardless, one dishwasher cycle likely will not cause irreversible damage.

If you accidentally run your skillet through the dishwasher, Stubblefield and Affoumado recommend these steps to restore it:

1. Check for structural damage: Before investing time in restoring the pan, make sure it is not warped or cracked.
2. Remove any visible rust: Scrub away rust with steel wool and warm, soapy water. If that doesn't work, Affoumado recommends soaking the pan in a solution of equal parts vinegar and water for no more than 30 minutes at a time.
3. Dry it thoroughly: When it comes to cast-iron care, moisture is the enemy. After scrubbing, dry the pan completely before re-seasoning. Removing all moisture will help prevent further rusting.
4. Apply a thin coat of oil: Pour a very thin, even layer of oil over the entire surface, inside and outside of the pan, the bottom, and the handle. Both experts recommend using a high-smoke-point oil, such as grapeseed, avocado, or sunflower. Wipe off any excess so the pan looks dull, not shiny.
5. Re-season the skillet: To re-season, Stubblefield advises baking the pan upside down at 450 to 500 degrees Fahrenheit for one hour to rebuild the seasoning. If needed, repeat the process to fully restore the skillet, Affoumado says.