Busting Cast Iron Myths

The Testing: When acidic ingredients are cooked in cast iron for an extended amount of time, trace amounts of molecules from the metal can loosen and leach into the food. Although these minute amounts are not harmful to consume, they may impart unwanted metallic flavors, and the pan’s seasoning can be damaged as well. To test how fast this happens and how noticeable it is, we made a highly acidic tomato sauce and simmered it in a well-seasoned skillet, testing it every 15 minutes to check for off-flavors and damage to the pan.

The Takeaway: In the end, our tasters could detect metallic flavors in the tomato sauce only after it had simmered for a full 30 minutes. So, while you can definitely cook with acidic ingredients in your cast-iron skillet, you have to be careful. First, make sure your pan is well seasoned; seasoning keeps the acid from interacting with the iron—to a point. An acidic sauce can afford a brief stay in a well-seasoned pan with no dire consequences. You should also be careful to remove acidic foods from the skillet after they finish cooking; don’t let them sit too long in the warm skillet and transfer any leftovers to an airtight container. (These rules do not apply to enameled cast-iron skillets; the enameled coating makes it safe to cook acidic ingredients for any length of time.) If you accidentally oversimmer an acidic ingredient, you may have to throw out the food, but you can simply re-season your skillet and get back to cooking again.

The Testing: To see just how the pans reacted when placed over heat, we spread 1 tablespoon of all-purpose flour in both our favorite cast-iron skillet and a traditional stainless-steel skillet and heated them over medium heat until the flour started to toast. As the flour browned in the hot pans, it essentially created a map of how each skillet heated up.

The Takeaway: While the flour in the stainless-steel skillet toasted evenly to a uniform golden brown, the flour in our cast-iron skillet started to burn in some spots before other areas of the skillet had any browning at all. It turns out that because cast iron is such a poor conductor, it in fact heats very unevenly on the stove—and more or less so depending on the level of heat you use. To work around this, we preheat the skillet in a 500-degree oven when we need a really good, even, fast sear. The better heat distribution in the oven helps the pan heat more evenly, creating a superior surface for searing. For recipes where a strong sear isn’t necessary, we preheat the pan for either 3 or 5 minutes over medium-high heat on the stovetop, which we found to be the best way to get relatively even heat without too much work.

The Testing: Because cast iron is so durable, old cast-iron pans are a common find at thrift stores, antique shops, and flea markets. But older cast iron may not always be in tip-top shape. To find out whether even the most damaged cast iron could still be salvaged, we took the most abused skillets we could find; completely stripped them of all their dirt, rust, and ruined seasoning; and then tried reseasoning them from scratch.

The Takeaway: It takes a lot to kill a cast-iron skillet. If yours has a crack in it from improper use or storage, or if it has literally rusted through, it’s time to throw it out, but unless the structure of the pan has been truly compromised, there isn’t much that can “ruin” cast iron. Even if the seasoning gets seriously marred or the pan starts to rust, you can clean it off and start fresh.

The Testing: We always test our cast-iron recipes on both gas and electric stovetops since some people think that cast iron and electric stoves don’t mix well.

The Takeaway: We mostly found that cast iron works great on electric, although it may take a little longer to achieve the same results since cast iron is slightly slower to heat on an electric heating element. If you’re using a cast-iron skillet on an electric range, you may find that you need to cook things slightly longer—use the upper ends of the timing ranges given in our recipes. If you have a glass-top range, you should also take extra care when moving the heavy cast-iron pan around on the stove to avoid any scratching or damage.

The Testing: During our extensive recipe testing in cast iron, we generate hundreds of dirty skillets. While developing our recommended procedure, we experimented with a variety of cleansers, including dish soap and scouring powders.

The Takeaway: We found that a few drops of dish soap are not enough to interfere with the polymerized bonds on the surface of a well-seasoned cast-iron skillet. Don’t scrub the pan with abrasives like steel wool or use harsh cleansers like Comet, and don’t soak the pan, since those things can definitely affect the seasoning, but it’s OK to use a few drops of dish soap if you need to clean up a particularly greasy pan, or even if that just makes you feel more comfortable with your cast iron. Just make sure you rinse the pan clean and wipe it dry when you’re finished.