How To Properly Season Cast-Iron Cookware
First, wash your cast iron cookware. This is the only time you will need soap to clean it, but you want to be sure you remove any dust or dirt. If you have a brand new cast-iron piece, you will need to do this to remove the wax coating that is on it to keep it from rusting until it’s seasoned.
Coat your piece in some type of oil. Warm up your cookware before oiling to open up the pores. Cast iron has a porous surface. The seasoning process will fill and smooth the surface to make it non-stick. Some type of oil is used to facilitate this process. Traditionalists would use lard. You can use plain old cooking oil, too, but you will get better results with Crisco. You want to coat the entire cooking surface with the shortening. Don’t glob it on, but every nook and cranny should have a nice, medium layer of shortening. Use about as much as you would use to coat a cake pan for baking.
Bake it in the oven. Next, you just pre-heat your oven to 350 degrees and put your cast iron pan in for an hour or so. After heating, turn off the oven and let it cool completely while still in the oven. Then it’s ready to go.
Only clean with hot water and a stiff brush, don't use soap. The soap will take the oil out and un-season your pan. After cleaning, rub a bit of oil or lard on the pan before putting it away. This way, it will season a little more very time you use it. The more you use it the better it will get.
Re-seasoning a used cast iron piece? If you buy a cast iron piece second hand, the process is still basically the same to re-season it, with one exception. First wash it in hot soapy water, as above. Then I put it in my oven on the highest setting (or on the self-cleaning setting if you have one) and let it bake for a few hours without any oil or shortening. This will remove any rust and the old seasoning. Let it cool, then follow the steps above to re-season.