I made the mistake once of leaving Canola oil on one of my good iron skillets for "seasoning" and such. Man you sure aint kidding about that stuff being rough! That stuff was literally like super glue! I finally broke down and took some steel wool and took it down to the bare metal and had to start from scratch again "seasoning" that skillet. If it hadn't been one of my Moms that was older than dirt and a perfect skillet for frying chicken I would have tossed the thing.