Heavy cast iron is a priceless treasure to be used and maintained year after year. In days of old there was a respect for things; you took care of what you had. Generations past held to the notion things were not disposable and not easily replaced. Their well used, well seasoned cast iron wares were often handed down to the next generations filled with memories of the home it came from.
My family has been using cast iron ware as far back as I can remember. Grandmothers and great-grandmothers passed their wares on to us as we each married and acquired homes of our own. Virtually nondestructive, cast iron ware will no doubt outlast us, nevertheless, it does need some care.
Iron ware is used every meal, every day in my kitchen. Most often it is maintained by wiping out debris with a dry cloth and swiping a bit of oil across the cooking surface. This keeps it clean and well seasoned for the next use. Deeper cleaning is done yearly..a good once over with salt and a luffa scrub, a rub all over with some oil and an overnight in the oven (100 degrees). Deep cleaning restores and nourishes the dark cast and deep seasons the surface.
Let me add a note here. If there are layers of rust deep in the pan or if the pan is dimpled with gunk or rust flakes I slather it with oil and throw it in a fire or grill pit for an hour. Once it cools I use sand paper to scrub the surface well- removing the rust/gunk only until we have a smooth surface to work with. From here I start the oil/salt cleaning and then on to seasoning.
Rusty pans need to be rust free before 'seasoning'. Once the salt/oil routine above is finished, wiping iwth a clean towel should show no signs of the rust. If it does, I the process again. After the pans give a clean towel it is time for a healthy seasoning. Here, I heat my oven or outdoor grill to around 400 degrees while rubbing down my cast iron ware inside and out with oil or shortening/lard. Aluminum foil on the rack of the oven or grill will help catch any dripping that occurs during the curing. Pans are placed upside down and left for one hour. Heat is then turned off and the pans are left until they cool completely.
A well seasoned pan after curing will be dark black with a nice sheen to it. If the pan was extremely rusty or damaged (i.e sandpaper had to be used) the pan will look dry or "off" so repeating the seasoning process (oil/oven one hour) needs to be done until the pan develops a black "sheen" to it. The worst pan I ever restored only needed the process done twice. For a new pan that was unseasoned (grey when we bought it), this curing process seasoned the pan with only two runs.
As my children grow and leave home, the gift of well tended cast iron goes with them.