This post probably should have happened a long while ago. None of my friends or family members have ever asked me for my thoughts on how to fill an apartment with smoke while cooking pizza or how to pickle daikon but more than once I have been asked for ideas about caring for my favourite type of cookware: cast iron. And what better reason is there for having a website than being able to answer fairly complicated questions (to which, as you’ll see, I don’t definitely know the answer) with the words “uh…see my post about that.”
Cast iron pans are manufactured by pouring molten iron into molds made from sand. This process and the nature of the metal creates surfaces (both cooking and outside) that are full of tiny pits and peaks. Obviously, iron is susceptible to rusting when exposed to water in food or damp environments. Luckily, fat if cooked hot enough and for long enough will bond to the metal and form a polymer-like coating. This coating can serve two purposes: It will fill the microscopic pits and make the cooking surface smooth and therefore practically non-stick and by excluding water will protect against rust. This coating can be created over a long period of frequent, high-fat cooking but for those of us who don’t cook bacon for breakfast every day and don’t deep-fry enough to have a permanently-designated “chip pan’ that sits by the stove full of oil (basically everyone, right?) an original seasoning grants a welcome headstart.
Methods for seasoning cast iron are surprisingly different and contradictory. By my estimation, ninety-five percent of experts (self-decreed or more widely recognised) agree that the process involves spreading a (very) thin layer of fat over the piece of cookware before it goes into the oven for a given amount of time. The three variables that come into play–and cause a wide margin of disagreement–are type of fat, oven temperature, and curing time. Incidentally, the other five percent add some sort of sugar to the mix either in the form of straight table sugar or onions and this apparently produces very good-looking but also temporary results. Because long term use, cleaning, and storage patterns play such an important role it is next to impossible for someone to prove that their method is the right one. This post is going to be a description of the method I think works best. I’m working from the best elements of the system recommended by the user “ThreeGigs” in this chowhound thread.
Opinions on fat type are split between those who want the purest, most refined option (Crisco shortening) and those who see cast iron as a centuries-old traditional material and so demand a similarly antique fat (lard or olive oil). I have tried Crisco and the results were just alright so I switched to lard this time. The only difference I observed was a more pleasant smell coming from the oven. So, my advice would be to use whichever of the three (shortening, lard, or olive oil) you happen to have on hand.
In the past I have tried the ultra-hot method (oven at 500°F for one hour or more) but found that the coating tended to flake off. This time I’m going with the more moderate 400°F for half an hour and then an hour with the door closed to cool off. I am also used to seasoning cast iron upside down in the oven so that any excess fat drips off and doesn’t pool in the bottom. In the linked-to Chowhound thread ThreeGigs makes the good point that if turned upside down the fat can’t fill the pits in the cooking surface and will just add to the peaks.
My dutch oven was showing some signs of superficial, surface rust (see the two previous pictures) . This is partly due to the usual reason that dutch ovens gets used less often than skillets and therefore are exposed to a higher ratio of ambient moisture to cooking fat. As well, I made the mistake of using its lid as a steam pan for bread baking (under the advice of a very good bread baking cookbook). Needless to say the cookbook should have said “use a cast iron pan that you don’t care about or even better an old and dingy brownie pan as a steam pan.” Removing the rust and reconditioning this pan will add an extra angle to this post.
First step is cleaning with soap and hot water and rust removal for the pans that need it. Ten minutes of soaking in a sink filled with a 4:1 ration of cold water to vinegar will help to loosen the rust. Steel wool or a very stout metal scrub brush are the best tools for removing surface rust. As you scrub the rust loose use a sink full of water or a slowly running tap to wash away what has been loosened. Under the brownish-orange rust the bare metal is a very dull silver colour.
Now the pans are set over very high heat for five to ten minutes. This dries them and causes the metal to expand (and its pores to contract) which drives out existing excess oil. The pans are cleaned again–carefully because they are very hot so they should be left to cool a bit and then still not dropped into water or they might shatter from the thermal shock
Some seasoning instructions call for heating the piece in the oven, dropping in a tablespoon or so of solid fat (shortening or lard) and spreading it around with a paper towel. This seems to me like a recipe for getting too much fat on the pan so instead I put the lard in a small skillet (that was also being seasoned but has the best seasoning to begin with) over low heat and used a wad of paper towel dipped in this melted lard to coat each pan’s surface. As per the ThreeGigs instructions I used a second wad of paper towel to wipe away the excess.
Each pan or pot went into the preheated oven right side up. After half an hour I turned the oven off and let the cookware cool a bit for another hour with the door closed. After the cool-down there was still some of the sticky, shiny streaks in places (they remind me a bit of the trails raindrops leave on a car window) but I think I have found the solution to this problem: While the pans are still warm use a clean wad of paper towel to buff these away.
For a more thorough seasoning I repeated the following steps: I applied a second coat of lard, wiped away the excess, heated for thirty minutes in a 400°F oven, turned the oven off and let cool for an hour, and then buffed away the streaks.
Lodge cast iron now comes pre-seasoned but an original home seasoning still helps improve the base coat. The best route to a shiny black, almost entirely non-stick, cast iron pan is high-fat cooking. How often you will have to re-season your pan will depend on the ratio of seasoning-positive cooking you do (deep-frying, frying chicken, cooking bacon or hamburgers, etc.) vs. how much seasoning-negative cooking you do (mainly cooking with acidic ingredients like tomatoes and wine). Once a year seems about right until you achieve the desired shiny, slick surface.