Hi Nancy: Paul is the expert on cast iron around here. I read his article on cast iron and Ive been finding and cleaning old cast iron around the house all day -- I was so inspired.
He does not mention this method though:
http://www.youtube.com/watch?v=GKYViowWP5w&feature=related Coca cola - like naval jelly - both contain phosphoric acid which will convert iron rust (iron oxide) to iron phosphate.
Using Paul's instructions Ive found this method works on even really old and crusty cast iron.
Heat the pan -- I am using a gas stove. Use a low heat but leave the pan on the burner until it is really hot. After 10 minutes or so use heat proof gloves to remove the pan to a
cooling surface. Put another pan over the flame if you have a lot of them. After the pan is cool
enough to handle use a steel scraper, a steel spatula, a razor blade scraper, dental tools, a wire brush, or wire brush and drill or whatever you like to clean off the cooked rust.
It comes off really easily but it makes a big mess. Wear safety glasses if you use a wire brush. Then put the pan back on the flame and pour in about 1 T coarse salt.
Spray a folded paper towel with a spritz of canola oil (or dip in lard or whatever you are using). Scrub the salt over the pan's surface with the oily paper towel. Wipe the pan down with fresh oil and paper towel until you no longer see black, or until you get tired of doing it. The heat will sterilize any disgusting stuff that has been in the pan.
Hang the pan up from a pot hanger and keep it handy to use. Never use
soap or
soap and
water on the pan. Just rinse out quickly under
hot water and repeat the wipe-down with oil and salt after heating the pan, and then hang it back up on a dedicated hook.
Have fun and buy more iron pots! There is so much iron out there rusting away and it needs a good home!