If you accidentally wash a cast iron, you can still save it. First, rinse the pan with hot water and dry it with a towel. Then, pour 1 cup of kosher salt into the still-warm skillet and use a paper towel or folded kitchen towel to scrub the pan with the salt until it appears clean. Rinse out the pan and dry it. If you want to use soap to clean your cast iron, it is okay to do so, but you will need to take a few extra steps to care for the pan so you don't have any rusty regrets. Avoid putting cast iron in the dishwasher.