I love, love, love my cast iron cookware! Cast iron is becoming such a hot cooking item again and I just wanted to share some information about cast iron cookware. Included in this post will be myths debunked mixed with history mixed with science! (I am such a nerd)
1. Cast iron is difficult to maintain. While cast iron can be a pain to start, once the pot, pan or dutch oven is properly seasoned, it is one of the easiest types of cookware to care for! I recommend either purchasing a pre-seasoned cast iron skillet from a reputable company (lodge is the oldest american manufacturer of cast iron cookware) and season it again anyway just for a little added extra goodness. 19th century American cooks typically used lard to season their cast iron because it was readily available and unsaturated enough to polymerize well. When an unsaturated fat is heated to high temperatures, especially in the presence of a good catalyst like iron, it is broken down and oxidized, after which it polymerizes, which means that it joins into larger mega molecules the same way that plastics do, and mixes with bits of carbon and other impurities. This tough, impermeable surface adheres to the pores and crevices in the cast iron as it is forming. The surface is non stick because it is hydrophobic (it hates water). Water soluble proteins is what makes food stick to pans therefore a hydrophobic surface prevents sticking. The bits of carbon in the seasoning may also act as an additional release agent. I have found some of the best cast iron cookware at garage sales for cheap and if you happen to inherit a cast iron skillet, you couldn't be more lucky. Cast iron cookware can last forever!
2. You should NEVER use soap to wash your cast iron. Many people think that when you season a cast iron skillet that the non stick is actually a layer of oil that is cooked onto the pan. In all actuality, it is not oil cooked onto the pan. It is a thin layer of polymerized oil or fat and there is a key distinction between the two. When a pan is properly seasoned, meaning that is has been rubbed with oil and heated repeatedly, the oil has already broken down into a plastic like substance which has bonded to the surface of the cast iron. This polymerized fat layer is what gives the cast iron its non stick feature and the material is no longer oil or fat. Because of this chemical binding, the surfactants in dish soap should not affect it. One thing that you should NEVER do is to leave your cast iron sitting in water.You need to try to minimize the time that it takes from start to finish when cleaning cast iron, to when you dry and re-season your pan. Just another tidbit about seasoning, Flax Seed Oil is one of the best oils to use for seasoning any cast iron. This is because it is the only "drying" oil that's edible. For more information click here.
3. Don't use metal utensils in your cast iron. Why not? This polymerized layer of oil or fat is tough as nails and chemically bonded to the pan. If you see black flakes coming from your pan, it is very very unlikely that it is seasoning. More than likely the black flakes coming out of your pan is carbonized bits of food that were stick to the surface of the pan. So scrape away with metal utensils, unless you are scraping so hard that you are gouging into the surface of the metal. So maybe use wood utensils if you are having a "glass of wine or two" kind of day.
4. New cast iron is as good as old cast iron. Cast iron has been used since before the Han Dynasty in 5 BC. Back then it was used for things from monumental statues to woks. Cast iron pans were used as early as 206 BC and were used for salt evaporation. Cast iron cauldrons and cooking pots were invaluable kitchen items for their durability and their ability to retain heat, thus improving the quality of cooking meals. Before the introduction of the kitchen stove, meals were made and cooked over a hearth or fireplace and the cookware were designed for use in the hearth. The first cast iron pots and pans were designed with feet or legs so that it could be set over the coals. The flat bottomed design did not come about until the introduction of the modern cooking stoves became popular in the late 19th century. The production methods have changed through the years and most cast iron companies no longer cast in sand molds like they did in the "olden days". Vintage cast iron has a satin smooth finish whereas the newer cast iron has a bumpy surface because the production dropped the previous sanding step. With proper seasoning techniques, your new cast iron skillet will take on a nice non stick finish but will never be as good as the vintage. For this reason, I like to stick to garage sales for older cast iron pieces.
~An added science/history bonus!
There are 3 types of cast iron. White cast iron, malleable cast iron, and grey cast iron. The white cast iron is used for items such as coins. It is the most brittle of the cast irons and although this iron is harder than quartz you have to be careful as to not drop it or it may shatter. Malleable cast iron is heated at a high temperature for days so that it causes the iron to precipitate as graphite making a material which has much better mechanical properties than ordinary cast iron. Grey cast iron is the most common cast iron used today. It has a graphite micro-structure. Grey cast iron is the type used for cast iron cookware because of its high thermal conductivity and specific heat capacity. this is also the reason that it is used for disk brake rotors. Grey cast iron is also used for housing where the stiffness of the component is more important that its tensile strength, such as internal combustion engine cylinder blocks, pump housings, valve bodies, electrical boxes, and decorative castings.
For more information
The Metallurgy of Cast Iron
Heavy Metal: The Science of Cast Iron Cooking
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