Best Way to Season Cast Iron Pans - Flax Seed Oil

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Introduction: Best Way to Season Cast Iron Pans - Flax Seed Oil

I try to use cast iron cookware whenever possible.  It has excellent heat dispersion properties, life long build quality, and an inherent ability to cook foods with exceptional control at both high and low heats.  It works on all kinds of stoves, electric, gas, induction - even a fire pit while camping.  

The only snag about cast iron (if you can really call it that) is the seasoning process.  "Seasoning" cast iron refers to a process of building up some amount of material, which I'll call a finish on the pan that aids in cooking, creates a semi-nonstick surface on the pan,  and protects the cast iron pan against any possible rust.

There are lots of theories on seasoning cast iron, from complex rounds of heating and oiling with different types of vegetable and animal fats, to doing nothing at all.  Having tried many of these seasoning processes myself, I feel inspired to write about the flax seed oil method.  It's the most durable and straight forward seasoning process that I've found, and the science behind the process agrees.

Step 1: Flax Seed Oil

You can find flax seed oil in the refrigerator aisle at the grocery or health food store.  Flax seed oil is the edible version of linseed oil, a very durable, hard drying finish that painters and woodworkers have been using for a very long time.  As Cheryl Canter writes on her site: "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."

What that translates to in practical terms is a durable finish, that even after just a few coats and short term heating results in a deep glassy black seasoning on the cast iron that has held up to months of my daily usage and cooking abuse.  

As with any other cast iron pan seasoning, You don't want to use soap on the pan when cleaning it, but with this method, I've found that using a mildly abrasive sponge when doing the dishes doesn't seem to affect the finish at all.

Step 2: Oil the Pan

Pour a small amount of the flax seed oil into the pan.  Less is more with this stuff, so shoot for more than just a few drops, but no more than a tablespoon.  Start with a teaspoon and go from there.  Then, using a paper towel or rag, spread the oil evenly throughout all the surfaces of the pan, including the bottom of the pan, the sides, and even the handle.

The pan should have a slight sheen to it, but no standing puddles of oil or thick areas of build up.  If you're really feeling inspired, use your bare hands to spread the oil around and envision yourself back in the old world.  Follow the rule of thumb for any other finish - shoot for a nice thin even coat.  You can always apply more, and, as you'll soon see, you will.

Step 3: Bake at 500F for 30 Minutes

Place the oiled pan inside a 500F degree oven for 30 minutes.  Some sources say to heat the pan for longer, but, if you've put on a thin coat of oil I've found that 30 minutes is plenty long enough.

The pan will smoke a bit during this process.  That is completely fine and natural, your oven will not catch fire.
The hot flax seed oil will smell a bit strange.  That is also completely fine and natural, the smell will go away.

PRESS ON! 

Step 4: Repeat 4 to 7 Times

Once you've "cooked" the pan for 30 minutes, remove it from the oven and let the pan sit until it's cool enough to touch.  When you're sure it's not still hot, reapply a thin coat of oil using the same method described in step 2, put it back into the oven and cook it for another half an hour.  

Keep repeating this process until you've gone through as many cycles as you'd like.  I've found that 4 to 7 rounds was enough to result in a semi-gloss, beautifully smooth, tough, black finish that is ready for use.

Step 5: Do All Your Cast Iron at Once

Final tip - do all your cast iron pans at once.  In my opinion, if you're gonna crank the oven up to 500F for several hours and make the house smell a little funny, you might as well make good use of it and season all your cast iron cookware at once.  The good part is that you won't have to repeat the process very often.  I've been going on the same seasoning session for several months now and they still look great.

Step 6: Use the Gas Grill

*update 1/30/12*

I now feel foolish for saying that this was the "best way" to season cast iron without mentioning this important tip that was brought up in the comments: if you want to avoid making your house smell like smoking oil - USE THE BBQ!

What a great idea - thanks to everyone who suggested this.  Next time, I'm definitely gonna use the grill.

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170 Comments

Why does the "no soap" mantra keep coming up. I've been cooking on cast iron all my life and I use Ultra Dawn on mine after every use, usually using either a regular sponge, or one of those twisted stainless pads if it's really caked on crusty stuff.

I usually season it every two or three years, not because it needs it regularly but because it usually suffers some kind of abuse like having something salty left in it (usually soy sauce) overnight or if the patina gets too thick and I have to clean it in the self-cleaning oven and then reseason it.

I will agree that you never want to use a brillo or other abrasive cleaner (comet, chore boy, etc.) on your iron. It's not as much the metal but the "soap" is much too aggressive. If whatever is in there is that caked on, just soak overnight in the sink, clean in the morning and wipe dry without allowing water to pool on it.

Me, I just use olive oil to season it. Flax oil is "edible" but so is mineral oil and I wouldn't want to use that in my pan.

One thing that looks different from my pans is that the pans in the picture don't appear to have a machined inner bottom, they look more rough, direct from the mold. Perhaps that's just the camera, but when the bottom of your pan isn't flat, you need to fill all of the nooks and crannies with oil to keep stuff from sticking. You have to look a lot harder to find pans with machined bottoms.

None of this comment is meant to be disparaging to the original poster and I'm sure your process works well for you and your pans. But please be aware that too many people are scared away from iron because they think it's too temperamental. I put my iron pans and dutch oven into harms way (melting candy sugar, using soy sauce, scrubbing with dish soap, sauteeing directly on the grill, frying potatoes, caramelizing pork butts, all kind of hot, acidic, salty food and they come through it just fine with little more than an oil wipe down before use and another if it's looking "tired" after washing, followed by a quick heat on the burner to about 300 degrees, then let it cool off in place.

The reason you have to keep reseasoning it every few years is because you use olive oil to season it and you scrub it with Dawn or detergent often.

Mineral oil is 'edible' but indigestible; which makes it a good lubricant for constipation: that stuff ain't going nowhere but out. It also doesn't polymerize. Period. It cannot be used for seasoning.

Olive oil is fine, but people should bear in mind that the smoke point of olive oil varies widely with cold-pressed, virgin, extra virgin, extra-virgin acidic, etc., and it's slow to polymerize to get to a film condition. Flax oil is best for people who are seasoning their first pan. I happen to use the similarly-behaving walnut oil because I cook with it a lot anyway. Once you have a pan with a good ol' coating, re-seasoning goes well on the old film without much worry.

Is it safe to use flax seed oil that does not need to be refrigerated? My bottle says it is 100% virgin (or unrefined) flaxseed oil. It does not list any other ingredients. However, it does not require refrigeration. Safe to use for seasoning? Everything I'm seeing with regards to using flaxseed oil says to use the refrigerated kind.

As long as it is 100% flax seed oil, you can use it for seasoning. There are different approaches in storing flax seed oil. One is the supermarket approach, which basically is, "We don't care if the oil starts tasting awful". Try one of those 100% flax seed oils that are not refrigerated in the store. They all taste very bitter (still not rancid).

If stored properly, flax seed oil should not taste bitter at all. That can only be achieved by storing it at low temperatures right from the beginning.

Also, flax seed oil should not be stored longer than 4-6 weeks.

For seasoning a pan, the bitter taste is no issue.

The very thin layers of flaxseed oil, after each one is baked for 30 minutes at 500 degrees, are essentially no longer flaxseed oil. Or at least they are drastically changed flaxseed oil. The hard, shiny, dry surface of a seasoned cast iron pan is not going to "go rancid."

Mineral oil is great for seasoning cutting boards.

Olive oil will turn rancid so shouldn't be used for boards or seasoning cookware.

Vegetable oil never cures and is always sticky.

Flax seed oil is the only edible drying oil. For that reason it is great for seasoning cookware. I don't use it on the cutting boards because the entire point of oiling them is to prevent drying.

So flax seed oil for seasoning cast iron and mineral oil for seasoning cutting boards.

thanks for the explanation of WHY not to use mineral oil

Mineral oil is ingestible, I've been using it for years on my cast iron. I'm not sure where people come up with the nonsense they spew? As a side note: mineral oil is great for constipation; a tablespoon at a time. Not as a thin coat on cast iron!

First, I do not use mineral oil on my cast iron, for I have many kinds of vegetable oil handy, and for seasoning, tend to use one that doesn't smoke at too low a temperature. That said, there is absolutely no reason that one could not use a mineral oil for seasoning, if one use the right one. Food grade mineral oils are used in this country (but not in EU countries) on baking machinery, and if you were to eat much commercially baked goods regularly, you could be consuming up to about 80 mg (eight hundredths of a gram) of mineral oil in your diet. 100 mg of mineral oil is considered a safe limit for a person of average weight. Your body cannot process it, and too much can cause some adverse effects. So, go ahead, season pans with it, but always wipe away any excess that has not polymerized onto a surface or penetrated the surface. By-the-way, in this country, so-called food grade mineral oils, which I'll just lump as highly refined paraffin oils, are used on salad bowls, cutting boards, wooden serving utensils, etc. to minimize ingress of water and bacterial and fluids that could become contaminated by bacteria in the wood's pores. I suspect that this is not approved in the EU, where I think they are overly cautious. This could stem from the fact that less highly refined mineral oils are generally lumped with carcinogens in food use and on food preparation and processing surfaces. So, be careful, find out what your oils really are, and then make your informed choice.