Maintaining Cast Iron Cookware
When you are done cooking, clean your cookware. It is easier to clean if it doesn't sit for a long time. If it is still hot, make sure use very hot water, as cold water can crack hot cast iron. Usually well seasoned cast iron will quickly wipe clean with a little water; no need for soap, the high drying temperature with purify any bacteria. While soap has the potential to break down the seasoning, don't panic if you occasionally do use soap. It will be fine.
If you have neglected cleaning it right away, or if it has baked on food that is hard to remove, you can soak it for a few minutes and up to 15 minutes; however, don't do a long soak in water, or boil water in your pan as this can damage the coating of your cast iron.
Use a hard plastic pan scraper, if needed, to scrape food from the cookware. In the event that food is burned on and the above cleaning method doesn't work, you can use steel wool, or another metal scouring pad, however, you may need to re-season it to get it back in shape.
It's better to let dirty cast iron sit uncleaned for awhile, then to soak it for a long period of time in water.
Drying #1: When cookware is clean and still wet, place it on a burner heated to high heat. When water has almost evaporated, always add a fat and spread it around with a paper towel to coat the inside of the cookware. See my comment in seasoning about the type of fat. Let it heat just until it begins to smoke, or 1-2 more minutes. Turn off heat and allow to cool before putting away. If there's any fat pooled in the cookware, give it a wipe with a paper towel. This process will keep your cast iron cookware seasoned and in great condition.
Drying #2: One word of caution, don't leave the room when heat drying your pan! It just takes a minute, or so. If you do, you may get distracted and forget it, resulting in house damage, or an unhealthy accumulation of gas in the room when using a gas stove etc. I may, or may not be speaking from experience.
Drying #3: ALWAYS use heat to dry your cast iron cookware. Other methods of drying will lead to rust and a poor finish. Even a little drop of water can cause rust, so make sure it's dry!
This all seems complicated when you're new to cast iron cookware, but it's really one of the simplest and most enduring things you can do and well worth the effort!
Restoring Cast Iron Cookware
If cast iron is in pretty good shape, it may only need a scrub with steel wool. Then follow seasoning directions. However, if it is in need of more clean-up, I have listed a few ways to accomplish that below.
Completely submerge the cast iron piece in a solution of one part white vinegar and one part water. Soak for 30 minutes. Rinse and scrub with steel wool. Repeat if needed, but do not soak longer than 30 minutes each time. Rinse, dry and follow directions for seasoning.
Soak in coke (yup, the beverage that no one should be drinking) overnight and scrub with steel wool in the morning. Then follow seasoning instructions. Ewe, if coke does that to a steel pan, what does it do to your insides?
If steel wool doesn't work, you can use sandpaper, or a wire brush.
If you're handy and have a grinder, you can try using that to take off rust and build-up. Alternatively, you could take it to an auto body shop and have it sandblasted, but this is really a last resort and only for extremely rusted cast iron. The auto body shop will usually charge a small fee to do this. Call ahead to see if are willing to do it and what they will charge. Then follow seasoning instructions.
Another last resort involves heavy chemicals, so I would try a lot of scrubbing with steel wool and sandpaper first, but here goes: Place cast iron cookware in a garbage bag outside in a well ventilated area, spray with Easy Off Oven Cleaner. Tie up the bag and let it sit for 1-2 days. Remove and scrub with steel wool, a wire brush, or sand paper if needed. Repeat if necessary for especially rusty and crusty specimens. Then follow seasoning instructions.
Some people recommend putting rusty cast iron in your oven on the self clean setting. I wouldn't recommend doing this. After having my oven serviced, the repairman advised me to not use the self clean cycle. He said it heats too high and it is very hard on the oven. He commented that it is a great selling feature, but oven producers know it will cut down on the life of your oven. Interestingly my service call was right after I had done a self clean.
Seasoning Cast Iron Cookware
Heat oven to 400.
Coat dry cookware with a neutral fat, preferably non-hydrogenated, organic lard, but don't be too concerned about the type of fat here. When you correctly season and maintain your cast iron, the fat you use will be transformed into a polymerized oil. It breaks down and bonds to the surface of the metal. It is more akin to a type of plastic coating than oil, or fat at this point. No harsh chemicals or complex industrial techniques required for this non-stick process to happen. Thumbs up from me!
Place cookware upside down on a cookie sheet. This keeps the fat from pooling up and becoming sticky.
Bake for one hour.
Let cool completely before removing.
Repeat this process, if needed, until you get a nice seal and coating. It will continue to improve as you use it and properly dry after each use.
Re-seasoning your cookware can be done anytime you feel it needs it. However, if you maintain it, you will likely never need to do this step again.
See more on cast iron cookware here.