Can you wash cast iron with soap?

The old rule says soap ruins cast iron. It came from a time when some soap was harsh, and from pans that were left wet until they rusted. People blamed the soap. The pan had been soaked. Seasoning is oil that has been heated until it bonds to the metal. A brief wash does not undo that bond. Steel wool down to bare silver does.

What a wash actually is

Wash the skillet while it is still warm, not after it has sat overnight with food glued on. Use hot water, a brush, and a small amount of plain soap. A cured tallow bar is fine. A scented bar is not what you want in a pan you fry eggs in. Rinse. The suds are there to lift stuck food. They are not a bath.

Dry it at once, on a low burner, until every drop is gone. If the surface looks dull and dry, wipe on a thin film of oil and heat it until the pan looks satin again, not wet. A puddle of oil in the cold pan turns sticky. Sticky is leftover fat. It is not seasoning, and it is not a reason to avoid soap next time.

What actually strips a pan

• Leaving it to soak until the next day.
• The dishwasher.
• Scrubbing to bare metal because a spot of food felt like failure.
• Putting it away wet. Rust is water, not soap.

A rusty patch gets a scrub, a dry, and a thin coat of oil heated on the stove. You do not need to strip the whole skillet because one spot went orange. And you do not need to serve last night’s grease as flavor. Food that tastes like old fish is not seasoning. Wash the pan.