시즈닝(seasoning)
season의 어원적 의미는 ‘때/시기’인데, 특히 ‘씨를 뿌리는 때(=time of sowing)’를 뜻한다. 이 season에서 나온 낱말로는 seasonable ‘계절에 알맞은’, seasoning ‘양념’, seasoned ‘양념이 잘 된’ 등이 있다. 거기에는, 씨를 뿌리고 수확하는 모든 작물이 때와 맞추어져야만 제맛을 내게 된다는 자연의 섭리(providence of Nature)가 담겨져 있다.
시즈닝(seasoning), 양념
조미료와 향신료를 배합하여 만든 양념. 집에서 고기를 구워먹을 때 쉽게 볼 수 있는 허브솔트 같은 것들부터 바비큐를 할 때 쓰이는 가루 혼합물, 감자칩 등의 과자에 뿌려지는 분말들까지 모두 시즈닝에 포함된다.
혼합된 가루 분말 형태로 판매되는게 대부분이며 롯데리아의 양념감자, 네네치킨의 스노윙 치킨이 시즈닝이 들어간 대표적인 음식이다. 요새는 이런 시즈닝들을 온라인 몰에서도 쉽게 구할 수 있어서, 집에서도 요리하거나 다른 음식을 찍어먹거나 할 때 쓸 수도 있다. 일부는 식자재마트에서 대용량으로도 팔기도 한다.
육제품 전면에 고르게 펴 발라주면서 입자들이 고기 표면에 흠집을 내주고 그때 손으로 톡톡 치면서 그 홈으로 들어가게 해줘야 한다. 그러면 최외부에 시즈닝 층이 생겨 조리되면서 나는 풍미와 향에 취할 것이다. 다만 너무 많이 뿌리거나 바르지는 말자. 양조절 못하고 그냥 듬뿍 뿌리거나 바르면 극강의 짠맛을 보게된다. 시즈닝 상당수의 베이스가 짠맛에 기반하기 때문. 즉 많이 쓰면 쓸수록 음식을 염분 덩어리로 만들어버린다.
흔히 스테이크 3원칙으로 일컬어지는 올리브유, 소금, 후추가 대표적인 시즈닝이며 인도나 베트남 같은 향신료를 잘 취급하는 국가들이 시즈닝의 천국이라 불린다.
양념감자
시즈닝 치킨
바비큐
시즈닝(seasoning), 조리 기구 관리법
시즈닝(seasoning)은 스킬렛이나 웍 등 내식성이 약한 무쇠(주철) 또는 탄소강 조리 기구의 표면에 기름 피막을 형성시켜 기구를 보존하는 것을 가리킨다. 흔히 '기름을 먹인다', '길들인다'고 표현한다.
원리
무쇠는 고온에 달구어질 경우 산소와 쉽게 결합, 산화하여 적녹을 형성한다. 현대의 무쇠 기구들은 일반적으로 제조사에서 제품을 출하할 때 기본적인 산화 방지 처리를 하지만, 스테인리스 스틸과 달리 본질적으로 내식성이 떨어지는 소재이므로 계속해서 사용하기 위해 사용자가 수시로 피막을 씌워 관리하는 것이다.
기름을 발라 가열하는 이유는 지방의 열산화를 이용해 일종의 천연 중합체(바이오 플라스틱)를 생성하고, 이를 표면에 코팅하여 외부 공기의 접촉을 최소화하는 원리이다. 시즈닝이 잘 된 기구는 부식에 강할 뿐만 아니라 기름의 성질로 인해 소수성을 띄고 재료가 잘 들러붙지 않게 된다.
방법
시즈닝을 하는 방법은 먼저 팬을 달군 뒤 기름을 매우 얇게 바르고 연기가 나기 시작할 때까지 가열한 다음 충분히 기름이 타면서 더이상 연기가 나지 않고 굳을 때까지 두었다가 식히는 것을 반복하는 것이다. 가스레인지나 오븐 모두 사용가능하며, 가스레인지는 오븐보다 시간이 적게 걸리며, 직접 불위에 올리는 만큼 고온에 도달하기 쉬워 발연점이 높은 오일을 사용해 시즈닝하기 좋다. 오븐은 사용시에 시간이 더 많이 걸리지만 시즈닝이 고르게 되며 얼룩이 적게 남는다. 화력이 좋은 가스 오븐이면 더 좋다. 이러한 과정을 거쳐 열에 의해 기름이 본래의 성질을 잃고 화학적 변화를 거쳐 중합체가 되어 코팅의 역할을 하게 된다.
시즈닝 후의 모습이 기름 막 같거나 충분히 견고하지 않다면 시즈닝이 제대로 되지 않은 것이다. 표면이 끈적인다면 기름을 너무 두껍게 바른 것이다. 이런 경우 싹 밀어내고 다시 시즈닝 해주는 게 좋다. 시즈닝은 기름을 고열에 노출해 지방산이 중합되게 해 표면에 단단한 코팅을 만드는 작업이다. 시즈닝이 제대로 되면 식기 세척기에도 견딜 정도로 단단한 막이 형성된다. 최대한 얇게 바르고 충분한 시간 가열하여 매트한 시즈닝을 얇게 여러겹 형성해야 한다. # 실제로 어떤식으로 시즈닝이 형성되는지 궁금하다면 간단하게는 스텐으로 된 팬이나 냄비바닥에 기름을 얇게 발라 태워보면 눈으로 확실히 관찰할 수 있는데, 너무 두꺼운 곳은 긁으면 쉽게 떨어져나가지만 얇게 잘된 곳은 시즈닝과 팬 표면의 철이 단단하게 결합되어 스텐뒤집개 등으로 긁거나 세제를 묻힌 수세미로 문질러도 잘 손상되지 않는다.
시즈닝 시 가장 좋은 기름은 첨가물 없는 아마씨유다. (flaxseed oil) 왜냐면 중합반응에 유리한 다가불포화지방의 비율이 높아 자유 라디칼을 가장 많이 생성하는 식품 등급의 건성유이기 때문이다. 하지만 아마씨유가 집에 없는 경우가 많을텐데 이럴 땐 같은 건성유인 들기름으로 대체해도 충분히 가능하다. 물론 건성유만 고집해야하는 것은 아니다. 해외에서 구할 수 있는 시즈닝 전용 오일들도 카놀라, 포도씨유 등을 비롯해 심지어 아보카도유나 정제 코코넛 오일[9] 까지 다양한 오일들을 베이스로 한 제품들이 많으며, 기름진 음식 조리시 자연시즈닝이 되기도 하는만큼 일반 식용유들도 가능하다. 물론 아마씨유와 같은 건성유가 끈적임이 적고 비교적 고온이 아니어도 시즈닝을 잘 만들어내기 때문에 시즈닝이 잘못될 확률이 적다.
그러나 아마씨유는 특유의 향이 강한데다가 일반적으로 발연점이 낮고, 가격도 비싸다. 이러한 단점 때문에 포도씨유, 카놀라유 등등 다른 오일을 더 선호하는 사람들도 있다. 포도씨유는 다가불포화지방의 함량이 풍부하고 발연점도 높아서 튼튼한 시즈닝을 만들어내며, 끈적임이 적고 매끄럽게되어 성능이 좋은 편이다. 게다가 쉽게 구할 수 있고 다양한 요리에도 사용가능하기 때문에 해외의 시즈닝용 오일 비교글에서 아마씨유와 함께 단골로 상위권에 위치하는 편이다. 구하기 쉽고 저렴한 카놀라유도 무쇠팬 제조시 프리시즌용 오일[12]로도 쓰이며 일반 가정[13]에서도 많이 사용한다. 쇼트닝 또는 밀랍이 들어간 왁스타입 제품들도 천에 적게 묻혀 얇게 바르기 좋아 선호하는 사람들이 꽤 있다. 중화권에서는 돼지기름인 라드도 많이 사용한다. 라드는 요리에 맛있는 풍미를 더해주는 시즈닝을 만들어낸다고 한다. 서구권에서는 전통적으로 베이컨 기름을 사용하기도 했다. 대신 동물성 기름으로 된 시즈닝은 방치하면 악취가 날 수 있으니 자주 사용하는 팬이 아니라면 사용하지 않는 것이 좋다. 결론적으로 다양한 오일들을 시도해보고 마음에 드는 오일을 찾았다면 자신이 선호하는 오일로 시즈닝 해도 문제가 없다.
시즈닝이 충분히 되면 조리기구의 표면이 소수성을 띄게 되므로 테플론 코팅이 된 팬처럼 음식이 팬에 잘 눌어 붙지않고 무쇠의 녹이 방지된다. 다만 대부분의 경우 사용시 충분한 예열은 해주는 것이 좋다. 코팅팬처럼 달구지도 않은 팬에 기름없이 계란후라이를 할 정도로 매끄러운 코팅층이 만들어지는 것은 아니기 때문이다. 시즈닝이 된 무쇠팬은 반 코팅팬정도라고 생각하는 것이 좋다. 무쇠 뿐만이 아니라 카본스틸 등의 기타 금속 조리기구도 시즈닝을 해주면 좋고, 스테인레스도 시즈닝을 해서 쓰는 사람은 거의 없지만 가능하긴하다. 표면이 매끄러운 팬이나 그릴은 시즈닝시 얼룩이 잘 생기니 유의.
시즈닝 후의 관리
산성이 있는 재료를 조리하다 보면 시즈닝이 차츰 벗겨지게 되므로 시즈닝된 조리기구를 사용할 때에는 토마토, 식초 등의 재료는 어느 정도 피하는 것이 좋다. 그리고 소세지, 고기, 베이컨, 튀김 등의 지방 함유량이 높은 음식을 조리하는 것은 조리기구의 시즈닝을 보강해주는 효과가 있으므로 자주 사용해주면 좋다. 시즈닝된 조리기구는 사용하는 과정에서 코팅이 점점 더 두껍고 균일하게 되므로 시간이 지나면서 점점 더 성능이 좋아진다.
시즈닝된 조리기구는 물과 부드러운 수세미로 세척하는 것이 원칙이며, 연마제가 함유된 수세미나 철수세미와 같이 표면을 직접적으로 갈아내는 것은 피막을 손상시킨다. 다만 음식물이 타서 심하게 눌러붙었을 경우나 녹이 발생했을 경우에는, 다시 시즈닝을 한다는 전제 하에 연마제가 함유되어 있는 초록 수세미나 철수세미 등으로 표면을 벗겨낼 수 있다.
뜨거운 물에다가 세척솔이나 아크릴, 스펀지 등 부드러운 재질의 수세미를 사용해 살살 씻는 것이 좋다. 후라이팬 용으로 나온 스크래치 프리 제품들도 좋다. 시즈닝이 어느정도 되어있고 팬을 충분히 예열을 해서 사용했다면 큰 힘을 들이지 않아도 잘 씻겨져 설거지가 쉽다. 세척 후에는 불에 올려 달구어 반드시 물기를 날려주어야 한다. 또 자주 사용할 경우에는 어느 정도 시즈닝이 잘 되어있다는 가정 하에 생략해도 되지만, 가끔씩만 쓰는 팬이거나 한동안 사용할 것 같지 않은 경우에는 녹방지를 위해 기름을 두껍지 않게 몇방울 정도로 얇게 발라서 보관하고 생각날 때 가끔 꺼내서 기름을 재도포해주거나 불에 올려서 습기를 날려주면 좋다. 사용시 보관용 기름은 뜨거운 물로 씻어내고 물기를 닦아 쓰면된다.
세제의 경우 제대로 시즈닝이 되어 있다면 기름이 이미 단단한 고분자화합물로 변한 상태이므로, 시중의 주방세제를 가끔 사용하는 것은 문제가 되지 않는다. 대신 물에 오래 담가 두는 것은 피해야 한다. 뜨거운 팬을 찬물로 식히는 것도 시즈닝에 금이가는 등의 손상이 가기 때문에 금물이다.
시즈닝 유지를 위해 기름진 음식 조리 후 설거지를 아예 안 하고 물로 닦아내기만 하는 경우도 있는데 위생상 좋지 못하다. 물로는 기름 찌꺼기를 완전히 제거할 수 없기 때문이다. 동물성 지방은 방치하면 박테리아가 증식하여 냄새가 나며, 남은 기름들이 오랫동안 쌓이면 시즈닝이 뭉치거나 끈적하게 변하기 쉬워진다. 시즈닝 자체는 섭취해도 크게 유해하지 않으나, 그래도 두껍게 축적된 시즈닝들이 팬에서 떨어져 나와 키친티올 등에 묻어나거나 음식에 섞이지 않도록 주의하자. 시즈닝 층은 너무 두껍거나 끈적이지 않아야하고 닦았을 때 묻어나오는게 없도록 관리해주는 것이 번거롭긴 하지만 이상적이다. 물로 세척 후 남는 소량의 기름정도로 자연시즈닝을 시켜주는 것이 좋다.
Chemistry of Cast Iron Seasoning: A Science-Based How-To
In a previous post, I illustrated how I cleaned and reseasoned an antique cast iron popover pan. This was my first attempt, and my seasoning technique was somewhat haphazard because I couldn’t find consistent, science-based advice. I used a combination of organic avocado oil and strained drippings from organic bacon. This worked pretty well on the popover pan, which doesn’t have a polished surface. But the smooth inner surface of a skillet showed an unevenness of color and texture, and the seasoning wasn’t hard enough. It was too easily marred by cooking utensils or scraping against oven racks.
I wanted to understand the chemistry behind seasoning so I’d know how to fix this, but there is nothing that addresses this issue directly. A Web page on cast iron posted by someone similarly obsessed with the science gave me two crucial clues, the phrases “polymerized fat” and “drying oil”. From there I was able to find the relevant scientific literature and put the pieces together.
The pictures below are both of the same antique cast iron skillet. The “before” close-up on the left is from a picture of the skillet in my previous blog post on making German Pancakes. I stripped the pan with oven cleaner and reseasoned it based on my new understanding. The “after” close-up on the right shows the result.
Start With the Right Oil (It’s Not What You Think)
I’ve read dozens of Web pages on how to season cast iron, and there is no consensus in the advice. Some say vegetable oils leave a sticky surface and to only use lard. Some say animal fat gives a surface that is too soft and to only use vegetable oils. Some say corn oil is the only fat to use, or Crisco, or olive oil. Some recommend bacon drippings since lard is no longer readily available. Some say you must use a saturated fat – that is, a fat that is solid at room temperature, whether it’s animal or vegetable (palm oil, coconut oil, Crisco, lard). Some say never use butter. Some say butter is fine. Some swear by Pam (spray-on canola oil with additives). Some say the additives in Pam leave a residue at high temperatures and pure canola oil is best. Some say it doesn’t matter what oil you use.
They are all wrong. It does matter what oil you use, and the oil that gives the best results is not in this list. So what is it? Here are some hints: What oil do artists mix with pigment for a high quality oil paint that dries hard and glassy on the canvas? What oil is commonly used by woodturners to give their sculptures a protective, soft-sheen finish? It’s the same oil. Now what is the food-grade equivalent of this oil?
The oil used by artists and woodturners is linseed oil. The food-grade equivalent is called flaxseed oil. This oil is ideal for seasoning cast iron for the same reason it’s an ideal base for oil paint and wood finishes. It’s a “drying oil”, which means it can transform into a hard, tough film. This doesn’t happen through “drying” in the sense of losing moisture through evaporation. The term is actually a misnomer. The transformation is through a chemical process called “polymerization”.
The seasoning on cast iron is formed by fat polymerization, fat polymerization is maximized with a drying oil, and flaxseed oil is the only drying oil that’s edible. From that I deduced that flaxseed oil would be the ideal oil for seasoning cast iron.
As a reality check of this theory, I googled “season cast iron with flaxseed oil” to see what came up. The very first hit is a page written by a guy who seasons his cast iron cookware with linseed oil from the hardware store because it gives the hardest surface of anything he’s tried. (I’m not sure how safe that is; I don’t recommend it.) Below that were several sites selling traditional cast iron cookware from China, which they advertise as being “preseasoned with high quality flax oil”. I don’t know whether they really use food-grade flaxseed oil (which is expensive) or linseed oil from a hardware store. What’s significant is the claim. Seasoning with high quality flaxseed oil is something to brag about.
With this encouragement, I stripped one of my skillets and reseasoned it with flaxseed oil. As you can see in the picture above, the result was a dramatic improvement. The finish is smooth, hard, and evenly colored.
Seasoning Is Not Cooking: Different Principles Apply
The first time I seasoned a pan I chose avocado oil because it’s monounsaturated and doesn’t easily go rancid. It also has the highest smoke point of any edible oil, 520°F, so I could heat it in a 450°F oven without passing the smoke point. I knew that when cooking, you should never heat an oil past its smoke point because that causes the release of “free radicals”, which are carcinogenic. I was careful not to choose a polyunsaturated oil – and especially not an oil high in omega-3 fatty acids – because these are especially vulnerable to breakdown with heat and the release of free radicals.
Ironically, it’s for exactly these reasons that the best oil for seasoning cast iron is an oil high in omega-3 fatty acids – in particular, alpha-linolenic acid (ALA). Free radicals are actually what enable the polymerization. Drying oils, which produce the hardest polymers, are characterized by high levels of polyunsaturated fatty acids, especially the omega-3 fatty acid ALA.
The lard that was traditionally used for seasoning 100 years ago was much higher in ALA than fat from pigs today, because back then pigs ate their natural diet. Today they are raised on industrial feedlots and forced to eat grain, making their fat low in omega-3s.
Since lard is traditional but no longer readily available, many people substitute bacon drippings, but this is a bad idea. If it’s conventional bacon, you’re baking in carcinogenic nitrates. But even organic bacon is not good for an initial seasoning because it’s filled with salt.
The reason that Pam seems to work well in seasoning is that its main ingredient is canola oil, which is relatively high in ALA (10%), making it a “semi-drying oil”. Flaxseed oil, a drying oil, is 57% ALA. But it’s not a good idea to use a spray oil, no matter what oil it’s made with, because of its additives. You’re doing chemistry here. If you want good results, use pure ingredients.
Fat polymerization can be triggered or accelerated in a variety of ways. As best I can tell from my reading, the cast iron seasoning process is an example of “radical polymerization”. The process is initiated when something causes the release of free radicals in the oil. The free radicals then “crosslink” to form the tough, hard film you see in a well-seasoned pan.
So what is the “something” that initiates the release of free radicals in fat? Iron, for one thing. High heat, light, and oxygen, for some others. To prevent cooking oils from going rancid – i.e., breaking down and releasing free radicals – you need to store them in dark, tightly sealed containers in a cool location. To initiate or accelerate the release of free radicals, put the oil in contact with bare iron and heat it above its smoke point, which will cause even non-drying oils to release free radicals.
I haven’t defined “free radical” or “crosslink” because that gets into details of chemistry that you don’t need to understand to season a cast iron pan. All you need to know is that the molecular structure of the oil changes and becomes something else, something tough and solid. The process is initiated with the release of free radicals, which then become crosslinked, creating a hard surface.
Free radicals are carcinogenic inside your body, and also a cause of aging. So don’t ever heat oil you’re going to eat above its smoke point. If the oil starts to smoke, toss it out and start again. When you’re seasoning a pan, you’re not cooking food. By the time the seasoned pan comes out of the oven, there are no more free radicals.
The Recipe for Perfect Cast Iron Seasoning
The basic idea is this: Smear a food-grade drying oil onto a cast iron pan, and then bake it above the oil’s smoke point. This will initiate the release of free radicals and polymerization. The more drying the oil, the harder the polymer. So start with the right oil.
Go to your local health food store or organic grocery and buy a bottle of flaxseed oil. It’s sold as an omega-3 supplement and it’s in the refrigeration section because it goes rancid so easily. Check the expiration date to make sure it’s not already rancid. Buy an organic flaxseed oil. You don’t want to burn toxic chemicals into your cookware to leach out forever more. It’s a fairly expensive oil. I paid $17 for a 17 ounce bottle of cold-pressed, unrefined, organic flaxseed oil. As it says on the bottle, shake it before you use it.
Strip your pan down to the iron using the techniques I describe in my popover post. Heat the pan in a 200°F oven to be sure it’s bone dry and to open the pores of the iron a little. Then put it on a paper towel, pour a little flaxseed oil on it (don’t forget to shake the bottle), and rub the oil all over the pan with your hands, making sure to get into every nook and cranny. Your hands and the pan will be nice and oily.
Now rub it all off. Yup – all. All. Rub it off with paper towels or a cotton cloth until it looks like there is nothing left on the surface. There actually is oil left on the surface, it’s just very thin. The pan should look dry, not glistening with oil. Put the pan upside down in a cold oven. Most instructions say to put aluminum foil under it to catch any drips, but if your oil coating is as thin as it should be, there won’t be any drips.
Turn the oven to a baking temperature of 500°F (or as high as your oven goes – mine only goes to 450°F) and let the pan preheat with the oven. When it reaches temperature, set the timer for an hour. After an hour, turn off the oven but do not open the oven door. Let it cool off with the pan inside for two hours, at which point it’s cool enough to handle.
The pan will come out of the oven a little darker, but matte in texture – not the semi-gloss you’re aiming for. It needs more coats. In fact, it needs at least six coats. So again rub on the oil, wipe it off, put it in the cold oven, let it preheat, bake for an hour, and let it cool in the oven for two hours. The picture above was taken after six coats of seasoning. At that point it starts to develop a bit of a sheen and the pan is ready for use.
If you try this, you will be tempted to use a thicker coat of oil to speed up the process. Don’t do it. It just gets you an uneven surface – or worse, baked on drips. Been there, done that. You can’t speed up the process. If you try, you’ll mess up the pan and have to start over.
The reason for the very hot oven is to be sure the temperature is above the oil’s smoke point, and to maximally accelerate the release of free radicals. Unrefined flaxseed oil actually has the lowest smoke point of any oil (see this table). But the higher the temperature the more it will smoke, and that’s good for seasoning (though bad for eating – do not let oils smoke during cooking).
I mentioned earlier there’s a myth floating around that vegetable oils leave a sticky residue. If the pan comes out of the oven sticky, the cause is one of three things:
You put the oil on too thick.
Your oven temperature was too low.
Your baking time was too short.
It’s possible to use a suboptimal oil for seasoning, like Crisco or bacon drippings, and still end up with a usable pan. Many (most) people do this. But the seasoning will be relatively soft, not as nonstick, and will tend to wear off. If you want the hardest, slickest seasoning possible, use the right oil: flaxseed oil.
10 Key Things Everyone Should Know About Seasoning, Cleaning, & Maintaining Cast Iron Pans
Cast iron is one of the best surfaces to cook on, but taking care of it is a whole 'nother story. It's not as simple as just washing it in soapy water like all of your other pans, and everyone has different ideas about how it should be done. It seems intimidating at first, but once you learn the basics, you'll be making the best steaks, homemade pizza, and fried chicken of your life.
But before you start cooking the best food you've ever had, let's go over some of the most important things you need to know about seasoning, cleaning, and maintaining your cast iron cookware.
#1
The Seasoning Is Super Important
The hard, black layer that gives cast iron its shiny finish is called the seasoning, or patina. As food scientist Harold McGee explains in On Food and Cooking, the patina is formed by the oxidization of fats, which causes them to "bond to each other...to form a dense, hard, dry layer." The metal is super porous, so the fats fill in the pores and seal the surface.
The seasoning prevents the pan from rusting and makes it nonstick. You definitely don't want to try using cast iron without seasoning—the porous surface makes it very sticky. Even if a pan says it's pre-seasoned, you'll get a better, longer lasting patina if you season it again yourself.
#2
Not All Oils Are Created Equal
You can technically use almost any oil to season your cast iron cookware. Bacon grease and coconut oil both work perfectly fine, but some oils result in a better patina than others. Sheryl Canter researched the chemistry behind seasoning cast iron and found that flaxseed oil provides the best possible nonstick surface.
As Canter explains, flaxseed oil is a drying oil, which means that it can form a hard film through polymerization. Drying oils maximize the polymerization of the fats, and flaxseed oil is the only edible drying oil, so it creates the best patina.
The downside to flaxseed oil is that it's expensive and can be difficult to find if you don't live near a health store. If you can't find it or don't want to spend that much, the next best thing to use is vegetable oil or shortening.
#3
Seasoning Can Be an All-Day Job
The process of seasoning cast iron cookware consists of coating it with oil, heating it in the oven, letting it cool, and repeating. It's up to you how many times you repeat, but the more you do it, the better your patina will turn out. Each time, the layer of oil gets a little thicker and a little shinier.
It's important to use a very light coat of oil. Seasoning a pan with too much oil will cause it to be sticky, and then you'll just have to start over. Place the pan upside down on the center rack in your oven with a baking sheet or foil underneath to catch any drippings.
Canter suggests cycles of one hour in the oven and two hours to cool. If you follow her method, make sure you have plenty of time—she puts her pans through a total of six cycles. But, if you don't feel like spending all day on it, you can get away with just one or two.
#4
It Will Eventually Need to Be Re-Seasoned
Even if you take perfect care of your cast iron, it will probably need to be re-seasoned at some point or another. When the seasoning starts to look dull (or someone accidentally runs it through the dishwasher), just wash it with warm, soapy water and a brush and repeat the seasoning process.
If your pan is rusty, you'll need to remove the rust first. You can use steel wool, let it soak in white vinegar and water, or even scrub it with kosher salt and a potato. Once the rust is gone, you can re-season the pan.
#5
It Can't Be Washed Like Other Dishes
Cast iron is incredibly durable, but the seasoning is much more delicate than the metal itself. In order to protect it, you have to be careful about how you wash it. You should never, ever put it in the dishwasher, and try to avoid using soap. If your pan is very well seasoned, a little bit of mild soap won't ruin it, but it could still damage the patina.
Avoid using steel wool or other abrasive cleaners (unless you plan on re-seasoning). Cast iron should never be soaked in water, and should always be dried thoroughly before storing to prevent rusting.
#6
It's Easiest to Clean While It's Still Warm
After spending a few hours in the kitchen, it's tempting to just leave the dishes to wash tomorrow morning, but that's the worst thing you can do with cast iron. Once you let it sit overnight, the food dries onto the pan and is much harder to remove.
If you clean your cast iron while it's still warm from cooking, a quick wipe with a cloth or paper towel may be all you need. For food that's stuck or burnt on, you can boil some water in the pan to loosen it. You can also use a stiff brush if the bristles aren't metal.
#7
Salt Is Great for Scrubbing
When you need to use some elbow grease, the best tool for the job is coarse kosher salt. Sprinkle some salt into the pan while it's still warm and add a splash of water to make a paste, then scrub with a cloth or brush to remove stuck-on food.
#8
You Should Oil It After Every Use
Once you've washed and dried your cookware, it's a good idea to apply a very thin layer of oil with a cloth or paper towel before you put it away. This helps to protect the metal and maintain the nonstick surface. To keep it dry and rust-free, line it with a paper towel prior to storing.
#9
There Are Some Foods You Shouldn't Cook in It
Foods with high acid content can damage the seasoning on your pans if used frequently. I occasionally cook something with tomatoes or red wine in my cast iron dutch oven, but some people would argue that even occasionally is too much.
In addition to damaging the pans, acidic ingredients can taste metallic when cooked in cast iron. Everything you cook in your pans absorbs a little iron from the cooking surface, and the reaction with the acid can affect the taste of the food.
#10
It Just Gets Better with Time
Don't be discouraged if food sticks to your cast iron the first few times you use it. If properly taken care of, the seasoning will only get better with time. The best thing you can do for your pan's finish is to cook with it as often as possible. Eventually, you may not even need to use oil anymore.