If you want to completely strip an old pan and start over put it in your self cleaning oven upside down and Put the oven in self clean mode. It will burn everything off the pan. Then thoroughly rinse and scrub off the powdery residue with hot water and a stiff brush. Put the pan on a burner and heat it up to boil off the water then coat with peanut oil or other high temp oil. Use a lint free cotton bandana or those blue “shop towels“ that come on a roll at Home Depot. Never use paper towels which will leave lint behind. Wipe off all the excess oil with your lint free cloth then put in a 300 degree oven for 1 hour. Repeat that step 3 times.