Soap may be safe, but you should never soak a cast-iron pan or use steel wool on it.
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Can You Really Use Soap On Cast Iron?

No doubt many grandmothers will want to scold us, but the truth is, soap isn't going to destroy your cast iron pans.
"To keep the cast iron enamel surface pristine, it’s best to use wooden, silicone, or heat-resistant silicone utensils," says ...
Nonstick pans are great for delicate foods, but if you need high heat for browning or searing, pick a different pan.
When dirty dishes beckon, soaking them in the sink seems the easiest solution. This is how long you should let dishes soak and why you shouldn't soak them at all.