I am a cast iron collector.
Soap is not so good. It sucks the seasoning out.
I say put a little oil in and put it on the stove top and get it smoking hot. Rub the oil in and repeat.
A new (100 year old) pan I buy I make a fire and get it real real hot put on thick gloves and rub grease on it with steel wool. Yes the steel wool catches fire too.. I get a deep seasoning this way that lasts a long time.
The iron should not look white when dry it should be black. Use a copper scrubber and water to clean, then ALWAYS dry on the stove top with a little oil rubbed in with a paper towel..
We cook 100% on 75 to 150 year old cast iron and dovetailed heavy copper cookwear...
NO Teflon no stainless///
I love it if in a bind, I can sell my cookwear for thousands.. It only goes up in value..
SO tell us about the markings on this pan... Is it old?
ON