Seasoning

Once we have the piece cleaned and down to bare metal, we need to get it seasoned, this is where it gets confusing for many, despite much of the information out there today, seasoning is not just a coating of an oil that has been heated up for a specific time in an oven at a specific temperature, usually said to be 350F, this misconception causes by far the majority of the problems people have with cast iron cookware with both cooking with it and cleaning with it. So what is seasoning and how do we do it?

The proper seasoning of a cast iron cooking piece is where a thin coating of oil is carbonized in a process similar to making charcoal, the volatile parts of the oil burn off leaving a polymer carbon coating (long chain molecules) that form a fairly non-stick surface on the top of the bare metal, filling the minute pores as well. Different cooking oils and fats carbonize at different temperatures; the point at where they start this process is called the “smoke point” because the volatile substances in the oils start to burn off creating the smoke. The carbonized oils left behind that coat the iron will not burn off till temperatures of 800 to 1000F are reached, beyond any normal cooking temperatures.

Today there are products on the market made and sold specifically for seasoning cast iron, I have never used any of these, and I have never had any problems seasoning cast iron with the different cooking oils and fats, many of those who have used them claim good results, but I have never had anything less than good results using normal cooking oils and fats, also if you think these products are some sort of magic, think again, they are mostly either soy bean/Canola oil for the liquid ones, or beeswax based for the solid ones with some soy or other oils added.

A quick check shows the liquid ones are about $7-$10 for 8 ounce, the solid is around $10 for 6 ½ ounce unless you decide to buy it in the handy container that looks like stick deodorant and then it is $10 for slightly over 2 ½ ounces. For comparison a bottle of soy bean oil in the liter size can be bought many times for around $1, I find this interesting because no matter what oil you use as we discussed above, you end up with carbon, also most instructions that come with these do not recommend heating high enough to fully burn off the volatile substances, this is not seasoning, but heated up oils.

The following is a list of some of the common cooking oils and fats listing the smoke point, (sources will show slightly different temps, it depends on the exact composition of the fat/oil which can vary slightly, and this is just a guide with averages). I really don’t have a favorite for actual seasoning, I normally use sunflower oil (cold pressed) because it is fairly cheap and I use it some in the kitchen, the bottle is easy to grab.

Safflower Oil…………………………510F/265C
Soybean Oil…………………………..450F/230C
Peanut Oil……………………………..450F/230C
Corn Oil………………………………….450F/230C
Sunflower Oil…………………………440F/225C
Beef Tallow…………………………….400F/205C
Canola Oil……………………………….400F/205C
Grapeseed Oil…………………………390F/195C
Lard………………………………………..370F/185C
Vegetable Shortening………………360F/180
Coconut Oil……………………………..350F/175C
Extra-Virgin Olive Oil…………………350F/175C

Although seasoning is not difficult, it is a step that many seem to have trouble with, one problem many have is when they are done, the piece is sticky and gummy feeling, this is a result of putting too much oil and fat on the surface before attempting to carbonize it as well as not getting the piece hot enough to carbonize the fats/oils. The other is the piece does not have a good non-stick surface, also a result of not getting the piece hot enough to carbonize the fats/oils fully.

Let’s address the using to much oils and fats first, I prefer cooking oils which are liquid at room temperature for seasoning, just because they are easier to work with on cold cast iron, I take a rag with the oil on it and I wipe and coat the surface to be seasoned with the oil, I then take a clean dry rag (paper towel will work) and I wipe as much of the oil back off as I can, just leaving a thin film. With a fat that is solid at room temperature it is best to heat the piece up above the melting point of the fat and wipe as much back off as you can just like the oil, one just has to be careful not to burn yourself in the process. The secret to seasoning is to not get more than a very thin film on it; any extra will just make a gummy surface. I have often seen it recommended turning the piece up-side down and putting a cookie sheet under the piece to catch any drips, but if you have enough that it will drip, you have too much on the surface already, it is better to remove all you can with the dry rag, it’s ok to do it up-side down, but if it’s on right it won’t drip.

So now we are ready to heat the piece up and carbonize the oils/fats, so how high do we heat it? Well if one wants to make it a bit scientific, then look at the smoke point of the oil/fat you are using and go a little higher than the smoke point, many sources today say 350F for seasoning which is barely the smoke point of the lowest oils and who is to say 350F on the dial is 350F inside, instructions often say to recoat it and heat it several times to build it up, done right it’s not needed.

I have found that no matter what oil/fat I am using, I put the piece in the oven, turn the thermostat to the last notch before the broiler kicks in and let it run a ½ hour or so or when it quits smoking. On my oven control it says 550F and my thermometer says it’s about 530F, I am not sure which is right, but when the piece cools I give it a thin coat of oil and it is ready to use. If you use the high temperature and really carbonize the oils, there is no need to repeat several more times; all you do is risk building up a heavy thickness that can even be prone to flaking off.

Our properly seasoned oven is now ready to use, forget these warnings about not using metal utensils in it, “you’ll scrape off the seasoning” if it does you didn’t season it right, as well as the one about no soap or acid foods.