Soaking a pan with water overnight is a sure recipe for rust, but a brief rinse or few minutes’ soak with warm water is fine. Use a firm brush, sponge, or non-scratch scouring pad to wipe out any bits of food; the flat edge of a metal offset spatula is helpful for stubborn spots. Once the pan is rinsed off, dry it thoroughly with a dish towel, and heat it on the stove for 10 minutes on low heat to evaporate away any lingering moisture.

According to old conventional wisdom around cast iron is that soap is the enemy. But most modern dish soaps, especially eco-friendly varieties, are perfectly safe so long as they don’t contain any polishing agents. If you have residue or strong flavors in your pan that you can’t eliminate with a stiff brush and some water, by all means lather up.

If you cook with your pan regularly (and wash and dry the cookware promptly), you likely won’t need to re-season your pan. Some substances like tomatoes, tamerind paste may cause the seasoning to come off.

Even a well-seasoned cast iron pan will rust if it’s exposed to prolonged moisture and air. That could mean a spot of water, an insufficiently dried-out skillet, or even humid air in a hot environment. The process is simple chemistry; in the presence of moisture, iron molecules react with oxygen molecules on a chemical level to form iron oxide, aka rust. Left to its own devices, this redox reaction will eventually convert the entire mass of iron into iron oxide. It would take decades for a hunk of metal the size of a cast iron pan to decompose, but iron oxide does weaken the atomic bonds in cast iron, and can eventually cause pitting that damages seasoning.

Research has shown an increased level of iron in foods cooked in cast iron cookware — especially high-acid foods that encourage the leaching of iron out of the pan, like applesauce, eggs, and tomato-based recipes. The greater the acidity of the food and the longer you cook it, the more iron is transferred. However, it’s very hard to measure the actual quantities of iron being transferred to your food, and a well-seasoned pan is less reactive to the acid in food.. So if you want more iron in your diet, it’s best not to count on the skillet for anything more than trace amounts and instead eat more high-iron foods or take suppliments.

It is practically impossible to dump your cookware as useless in ypur lifetime. Since you can create, maintain, and even repair the “seasoning”, your cookware can last 100 years or more. Chemical non-stick coating cannot be repaired, limiting lifespan. So Cast iron can be considered to one of the most sustainable options