Cast Iron....this is a versatile pan and there is no other pan that even comes close to its league. Cast iron pans do carry a myth-packed lore when it comes to their maintenance...like people who claim you have to treat your cast iron cookware like a delicate glass ornament to others who claim their cast iron is non-stick or dang, does my pan heat evenly! There are many unfounded and untested claims regarding our favourite cookware. Let's put a few myths to rest.
Myth #4: "You should NEVER wash your cast iron pan with soap."
The Theory: Seasoning is a thin layer of oil that coats the inside of your skillet. Soap is designed to remove oil, therefore soap will damage your seasoning.
The Reality: Seasoning is actually not a thin layer of oil, it's a thin layer of polymerized oil, a key distinction. In a properly seasoned cast iron pan, one that has been rubbed with oil and heated repeatedly, the oil has already broken down into a plastic-like substance that has bonded to the surface of the metal. This is what gives well-seasoned cast iron its non-stick properties, and as the material is no longer actually an oil, the surfactants in dish soap should not affect it. Go ahead and soap it up and scrub it out.
The one thing you shouldn't do? Let it soak in the sink. Try to minimize the time it takes from when you start cleaning to when you dry and re-season your pan. If that means letting it sit on the stovetop until dinner is done, so be it.