The Myth – Soap and Cast Iron

[Mike Shonfield]

The other day on the internet I came across a discussion on using soap on cast iron.  It was not a cast iron forum but a fellow named Dan, a retired chemist said it was old folklore to never use soap on cast iron and there was no scientific basis for it.

He said it stemmed from early settlers making soap and described in detail the chemistry behind that.  It was not the soap that removes the patina or seasoning on their cast iron kettles but the potassium or sodium hydroxide (alkali) that did it. By the early 1900's lye (or Sodium Hydroxide) became readily available in cans and was the raw material of choice for making soap.

He explained that patina development is a two part process. The first part involves developing a thin layer of polymerized oil on the cast iron. This is done by applying a thin coat of oil to the cast iron surface and heating it until it dries to the surface. When done properly this layer of polymerized oil CANNOT be removed by either soap or dishwashing liquid. The only way to removed this layer is by mechanical scrubbing (i.e. brillo pad), by caustics (lye, draino, or oven cleaner), or by burning it off at temperatures greater than 500 deg F (on BBQ pit or in Self Cleaning oven).

The second part to true Patina development on cast iron involves the actual lay down of carbon on the cast iron surface. This happens at temperatures slightly above the smoke point of the seasoning oil. You MUST heat cast iron above the smoke point to get actual carbon black into the patina.  If you do not heat to the smoke point you will only have polymerized oil in the coating........this is a protective coating but it is not as slick a surface as a mixture of both carbon and poly molecules.

He points to the fact that soap is not used to remove the baked on polymers in a dirty oven.  This is why oven cleaner and self cleaning ovens were invented.

To get a durable, non stick patina you must heat the oiled cast iron to high temperature (450) to get beyond the “sticky” stage to the “dryer” stage. He says the higher the unsaturates in the oil the more material is available for the polymer reactions.  Grapeseed oil is an oil that is apparently good for developing a hard polymer on the surface.

Dan if you are a member of WAGS stand up and identify yourself!

What do other WAGS members think?  Is this logic flawed?  Should I not use soap?

[Tom Penkava]

Mike, I agree with what you have found.  I have used dish soap to clean skillets & COs for years with no damage to the seasoning or patina, just spray/coat lightly when dry and they are ready for the next meal.
As for initial seasoning, I usually use the BBG outside and heat above 500 till the piece stops smoking, apply another coat and reheat.  Sometines 10-12 times for my COs.  With this methould I have had no problem with acidic foods like spagettie sause destroying the seasoning.
Have not tried grape oil, just crisco, canola oil, and/or pam.

[Mike Shonfield]

Good to hear Tom.  I am going to start seasoning at 450.  Too many of my pans have come out sticky.

He also says you need to season many times to build up patina.  The type of oil was not that important as long as you reached its smoke point.

[Sam Roberts]

I agree except for one thing, I wouldn't use a citrus based diswashing liquid for it will definitely mess up your patina.

[Tom Penkava]

I didn't think if that, but do agree.

[Charlee]

Can't help it, my mama woulda tanned my hide if she caught me using soap on her cast iron...  I just can't do it! ;D  

[C. Perry Rapier]

I'm with you Charlee. Everyone is certainly entitled to their own opinions, and I am of the opinion that dishsoap will diminish your seasoning. It seems to me, and this is just me, but if you have it seasoned good, you would not, or do not, need soap anyway.

[Mike Shonfield]

 ;D  Good job your Mama's didn't tell you the world was flat!  You would be afraid of slipping off! ::) ;D

[Charlee]

Mike...   :P   ;D  

I can taste the soap in the food when someone uses it on cast iron...maybe it's just a mental thing...dunno...but I usually am "suddenly full" when I find out that someone uses soap on their iron...

[Mike Shonfield]

Charlee,

I don't really know.  I am not an expert but I just found this article which I thought made a lot of sense.

His comment to the soap taste issue was that if the taste exists it is a function of the oil used and of not being heated to a high enough temperature when seasoning.

I would like to talk with the guy but it was a 2 year old article that would require me to sign up to the forum to find his email address and see if it were still valid.

[Harry Riva]

My mom always washed her cast iron skillets or, better put, I washed them since that was one of my jobs as a kid. My wife has always washed our cast iron because that's how her mom did it. Wash it and wipe or spray it with a cooking oil.
Harry

[Jeff]

Many years ago I used soap to clean a Griswold skillet--never noticed a problem. Perhaps as an abundance of caution I currently don't use soap on any of my cast iron pieces.

It is interesting to note that Lodge discourages the use of soap. From their website:

Cleaning your Lodge Cast Iron

After cooking, clean utensil with a stiff nylon brush and hot water. Using soap is not recommended, and harsh detergents should never be used.  

Perhaps their recommendation stems from the fact that all dish soaps are not the same, e.g., some may have citrus added, etc.  

[Jeff]

Maybe Lodge is using the term "soap" in the traditional sense as opposed to modern dishwashing detergents, i.e., they specifically use the term "harsh" detergents. So maybe the use of Dawn or something similar is not necessarily a problem. Guess I'll have to experiment with some mild dishwashing detergent and see what happens.

[Jesse and Kim Dunfee]

I can't think of anything right off that stuck in a pan enough to need the use of soap. Hot water in the warm pan usually does it. If I do have something real greasy I will put a "Drop" of dawn in the water in the skillet to break surface tension and disolve the grease............ :)

[Tom Penkava]

When camping "light", I will use the iron skillet to heat water with dish soap to clean the cooking/eating utensils, then rinse well/dry and oil.  No problems with the seasoning being lost.

Note:  ( more of a confession )  When we packed up after the cook out in Iowa ( convention ), it was too dark and late to clean up everything.  It ended up being 2 weeks later when I had enough free time to clean 9 COs.  Talk about colored hairy/fuzzy things growing.  Wiped/plastic scrapered most of that out, then filled them with hot tap water and dish soap, used dish rag ( wife makes them out of knited material ) to scrub everything good.  Then several thorough rinses with very hot water, dry and oil.  The seasoning looks as good as ever and have used most of them since with no problems.

[Mike Shonfield]

Here is my take on it from what I read.  If you cook much above  500 to 600 you run the risk of taking all the seasoning off. With a BBQ it is hard to control the temperature.   I clean newly purchased pans by running thru my self-clean oven where I understand temperatures are about 800 to 900.  Then I re-season.

If you go less than the burn-off-season temperatures you end up with black carbon stuck on the pan which may be harder to clean than the original food.

So I think you just clean with hot water and soap as soon as you can.

[Sam Roberts]

My 2 cents worth. If you're not comfortable just using hot water to clean your C/O, use soap and a sponge/rag. If it removes your seasoning, reseason it and don't use soap the next time. Problem solved.

[C. Perry Rapier]

My 2 cents worth. If you're not comfortable just using hot water to clean your C/O, use soap and a sponge/rag. If it removes your seasoning, reseason it and don't use soap the next time. Problem solved.

Sam, I like your style.  ;) And I totally agree with you.

I'll say this then shut up. Dawn, its good stuff, and it'll take everything but ugly off, and its trademark is it cuts grease. I know it'll cut the greasy buildup off of a piece of cast iron that somebody put vegetable oil on it instead of mineral oil for display purposes. Don't do that by the way. OH, I was gonna shut up.

But again, Sam, lovely lovely touch.  ;)

[Sam Roberts]

I wan't trying to end the thread. I just wanted to add my proposed solution to the problem.

[Hud]

This is a very interesting subject.  My concern is the flavor of soap leaching into food.