How to Clean Cast-Iron Pots
Cast-iron pots can rust if exposed to water for too long, so they need to be scoured and seasoned with oil instead.
Often touted as an item of cookware that can be handed down through generations, the cast-iron pot or Dutch oven requires a different cleaning approach than stainless steel or aluminum pots. The key is to protect or restore the seasoning that gives the pot its nonstick sheen.
Taking care of cast iron requires working quickly. Although noted for their durability, cast-iron pots have an Achilles heel in rust. Leave even a thin covering of sauce or liquid in the pot and rust spots can rapidly flourish.
- Ideally while the pot is still warm, loosen any large slivers of food or carbonized debris by scraping the pot with a plastic or wooden spatula and tip the lot into the garbage. While not quite at the level of Teflon, a seasoned Dutch oven releases tough, burnt-on residue much more easily than do other metals.
- Soak a sponge or cloth in warm, soapy water and wipe down the inside of the pot until the surface is clean and smooth. Try to keep the sponge or cloth damp rather than wet.
- Rub the pot dry with a sheet of paper towel. Even a single drop of water left in the pot can leave a noticeable rust spot.
- Transfer the pot to an oven preheated to around 300 degrees Fahrenheit, or put it over heat on the stovetop. After 10 minutes in the oven, or until the first signs of smoking on the stovetop, the cast iron will have released all its moisture and be completely dry, as well as sterile.
- Allow the pot to cool down and rub it lightly inside and out with vegetable shortening or lard, using a paper towel. The fats in the shortening contribute to the pot’s protective coating. Standard cooking oil is acceptable, but it tends to leave a sticky finish.
Myths abound about keeping cast iron away from water, soap and metal scouring pads, to the extent that some cooks even advise against boiling water in a Dutch oven. However, there is no question that leaving a Dutch oven to soak in water will cause rust and require a thorough revamp. A rusty cast-iron pot needs scouring and re-seasoning.
- Resurrect a cast-iron pot that has been left to rust by first scraping free any food debris with a spatula or stiff brush. For a pot that has been allowed to fester, for example, if forgotten outside after a barbecue, fill it with warm, soapy water and bring it to a simmer on the stovetop, then remove it from the heat and allow it to drop to lukewarm. Carefully work free any debris with a wooden spatula or brush before discarding the water.
- Wipe the pot clean with a damp cloth, then add a quarter of a cup of cooking oil and a cup of kosher salt. Using the cloth, or a paper towel, scour the inside of the pot, working the oil and salt all over the surface.
- Rinse the pot clean, dry it off, then place it upside down in an oven preheated to 300 F for about 10 minutes.
- Remove the pot from the oven and allow it to cool. Any remaining rust spots or tarnishes can be erased, surprisingly, by rubbing with a raw potato wedge or a cloth dipped in baking soda.
A pot that has turned to rust will have lost some of its protective coating, particularly after scouring clean, so the pot will need to be re-seasoned. The advantage of re-seasoning is that it will remove any lingering odors, such as curry powder or garlic, which can bond to the protective oil coating.
- Starting with a cast-iron pot that is scoured and dry, rub it all over with a paper towel dipped in vegetable shortening or lard. There is nothing to be lost by covering the outside of the pot as well as the inside.
- Place the Dutch oven upside down in an oven preheated to 450 F, the temperature at which oils start to form chemical bonds with the iron. Leave the pot in the oven for an hour, then turn off the heat and allow it to cool inside the oven, so that it comes back to room temperature slowly rather than suddenly.
- While warm, finish it off with a final coating of vegetable shortening and store it in a dry place.
Exposed to the high temperatures of seasoning, oil massaged into cast iron turns to polymerized oil, which is as resilient as plastic and cannot be removed by soap alone. Because the seasoning bonds to the iron rather than just coating it, even a scouring pad will not remove it.
Nick Marshall is a UK-based writer specializing in trends and best-practice in the B2B sector.