Pure home rendered hog lard is the only thing I ever saw my maternal grandmother use to fry or bake anything in her cast iron skillets.
Mom used Crisco solid vegetable shortening in a can sometimes but her cast iron skillet was already a slick, well seasoned hand-me-down.
We have my Mom's old skillet now and have used it for years.
Besides lard we've used all types of commercial liquid and solid vegetable shortenings but apparently it is so well seasoned from countless years of use nothing has affected the flavor of food cooked it yet.
To my knowledge it has never been washed with soap or an abrasive cleanser of any kind.
