by Sadge, at Firesign Farm
I love my cast iron skillets and pots. I have 10" skillet, 10" pot with lid that fits both, and an 8" skillet in my kitchen, plus an 8" footed camp oven in with my camping gear. With proper care, cast iron cookware lasts a lifetime - even centuries, if you're lucky enough to inherit the family heirloom pots and pans.
Cast iron is porous. To develop the coveted non-stick black coating on the cooking surface, the pores need to be sealed up, called seasoning. Once seasoned, and with proper care, the coating builds up with use, and your pan just keeps getting better and better. Soap, however, dissolves the non-stick coating, so if your pan has been washed with soap it will need to be re-seasoned. A new, or new-to-you, pan should be washed well, but just this once.
To season a cast iron pan, heat it on a stove burner until warm, and then rub the inside liberally with vegetable oil (or you can use a solid fat, such as lard or clean bacon grease). You want to thoroughly coat the surface, but with no pooling of the oil - the plan is to seal the surface, not set it on fire. Then put your pan in a warm (200º) oven for an hour or two. Again, wipe out any pools of oil, and you should be good to go. Historical note: I can't vouch for this, but one of my old books suggests boiling potato peelings in a cast iron pot for an hour to season it - might work, sealing the pores with potato starch - but I'll stick with my tried and true, oil and heat, method.
No soap! Do not use soap, detergent, coated Brillo pads, or any kind of de-greaser! Plain water works just fine! (Can you tell I had this conversation repeatedly with my husband when we were newlyweds? After twenty years, and a few ruined meals and re-seasoning sessions, I think I finally have him trained). Don't leave cooked food in a cast iron pan - the acids in some foods can pit cast iron, and the iron absorbed by the food can cause a metallic taste if left overlong. Transfer food to a storage container or serving dish, and then clean your pan right away. It doesn't need to be soaked in a sinkful of water for an hour, either. Scrape or wipe out as much food as possible, set it in the sink, and run some water into the pan, preferably while it's still warm. I keep a long-handled nylon-bristled dishwashing brush for cleaning my cast iron - just swoop around the inside of the pan, and rinse. If you really *need* some scrubbing power, pour in some salt or sand, moisten with oil, rub in with a dishcloth (or plain steel wool), and rinse (this method will also remove rust). As an absolutely last resort, I've read that you can fill the pan with warm water, drop in a couple of denture tablets and let set for an hour, and then rinse, without having to re-season it - not so sure about this one.
Drying the pan immediately is crucial too. Rust is the enemy of cast iron. Just like my grandma did, I dump out as much water as possible, and then put the pan back on the burner (or on the top shelf of my oven if I'm baking something), until all the dampness is completely gone from the inside of the pan. Let it cool before storing.
To keep rust away, cast iron is best stored so that no moisture can get inside. For my covered kitchen pan, I put the lid on the pan upside-down, a rolled towel between pan and lid on one side to provide an air vent. For my camping pot, I do the same, along with crumpled newsprint inside to absorb any chance moisture, and then loosely tie it in an untreated cotton canvas bag (also to keep any ashes on the outside of the pan from getting all over the rest of my camping kit). The skillets live in the drawer beneath my oven. If you use a pot rack, and wish to hang your cast iron, first make sure that your rack, plus its attachment to wall or ceiling, can withstand the weight. If, by chance, you do get rust on your cast iron, try removing it with the sand and oil treatment described above. Using naval jelly is a last resort remedy for removing rust - wash well and re-season before use.
I prefer to not use any silicon-based non-stick sprays on my cast iron. Over time and use, a black natural non-stick coating builds up inside the pan. I do keep canola oil in a little refillable dispenser (ok, it's an old rubber French's mustard bottle with a pop-off lid and a twist-close spout) and use a little squirt of oil before cooking most things, tilting the pan cover the bottom as it heats up. Over time, a black scaly crud will build up on the outside of the pan. This doesn't affect either the food or the pan, but if you just have to get rid of it, wait until autumn. Find someplace that still allows burning leaves, and bury your pan in the pile before setting it afire. Dig the pan out of the cooled ashes, wash, and re-season before use. You can also burn the coating off a pan in the embers of a campfire, but resinous woods such as pine can leave an aftertaste if any gets inside the pan.
One last note: All of a cast iron pan gets hot, and holds heat longer than most other cookware. So always use felted wool or heavy-duty cotton pot holders until you're sure the handle is cool. I found out the hard way that cheap, polyester-filled handle holders melt, taking a hot panful of skillet-sizzled cornbread out of the oven - I had to pick and scrape off the ugly little bits of white melted fluff. I also have melted little ridges into the plastic handles of my spatulas, leaving them resting upside-down against the edge of the skillet. Let's be careful out there.