A cast iron pan is an indispensable kitchen tool, and something that every home cook should own. Cast iron pans have a reputation for being high-maintenance, and many pan owners live in fear or somehow doing something that would render their prized heirloom unusable. In reality, however, cast iron pans are nearly indestructible.
If it gets rusty, the rust can be scraped off. If it loses its seasoning, it can be re-seasoned easily, and you can get back to cooking all your favorite cast iron dishes in no time. And contrary to popular belief, a small amount of dish soap can be used to clean a well-seasoned pan without affecting the seasoning. But there is one thing that you should absolutely never do to your cast iron pan: put a hot pan into cold water.
Thermal shock is a cast iron pan’s mortal enemy. When a pan is heated, the metal expands slightly, a process called thermal expansion. As it cools, it contracts. If you start a cold pan over low heat and let it heat up gradually, and rinse your pan with hot water and let it cool slowly after use, then all will be well.
But if you continually blast a cold pan with high heat or stick your hot pan into cold water right after taking those cast iron brownies out of the oven, you force the process to happen much faster than nature intended, with dire consequences. If this is a bad cooking habit of yours, you really need to cut it out immediately.
Just as hot glass can shatter when placed into cold water, a hot pan placed into cold water can buckle, warp or crack. And unfortunately, there’s no coming back from that. But while this may be the absolute worst thing you can do to your cast iron pan, there are other, smaller cast iron mistakes you might be making on a daily basis without realizing it.