About Cast Iron
Folk boiled wood ash extract to get Potassium Hydroxide for making a soft soap. By the early 1900's lye (or Sodium Hydroxide) became readily available in cans and was the raw material of choice for making soap. One of the advantages folk realized in using lye was it produced a hard soap and they didn't have to boil all of that wood ash extract.
Folk used cast iron vessels in which to boil the wood ashes or lye, with animal fat to produce soap. One of the observations they made in the soap making process was that it removed the seasoning of the cast iron kettle. This is where the folklore to "NEVER USE SOAP" began. The error here is that it is not the soap that removes the patina or seasoning on the kettle; rather, in reality it is the Potassium or Sodium hydroxide alkalie that removes the pot seasoning/p>
Patina development on cast iron is a two part process. The first part involves developing a thin layer of polymerized oil on the cast iron. This is accomplished by applying a thin coat of oil to the cast iron surface and heating it in an oven 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 vigorous 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 matrix. 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.
Keep in mind that grease splatter inside of an oven undergoes the same chemical reactions as what goes on in the cast iron seasoning process. If soaps or detergents really were able to remove seasoning from a pot, then cooks could actually clean the inside their ovens with Ivory soap or Dawn liquid soap/detergent. We all know that doesn't work and is why oven cleaner and self cleaning oven cycles were invented!
I use Dawn concentrated liquid (anti bacterial) when I need it. One doesn't have to use soap in all cleanings.....example fried eggs, fish, fries, etc. However, when searing steaks or applications where a good bit of buildup accumulates on the metal surface, I use soap with a plastic brush. I then follow this with boiling some water in the pot to again lift any remaining food particles or possible soap residue from the pot's surfaces and crevices. I then empty the pot contents.... continue to heat it on the burner to insure all water is removed (very important). Finally, I re-oil the pot while it is still hot.
When cast iron is seasoned properly, soap and/or detergents WILL NOT REMOVE it. It will only remove remaining cooking oil, fats, and help lift debris from the surface of the cast iron. I plan to add further to this thread in the future and share my take on proper seasoning and care of cast iron.
Cast iron is tough and can take the heat. What it cannot take is a sudden drastic change in temperature......this can crack it. Bake it in the oven at 500 degrees or run it through an oven cleaning cycle. Afterwards allow it to cool in the oven and you should have no problem with it cracking. Putting cool water into a 500 degree cast iron skillet or putting it onto a cold surface might crack it.
Curing cast iron is not rocket science. About 30 years ago an old Cajun camp cook told me that the best way to cure a pot was to "smoke it in the oven with lard" then use it as often as possible for frying (potatoes & fish) and making cajun roux in it.......especially making cajun roux in it. Today after curing many cast iron vessels from small skillets to huge wash kettles or cauldrons, I now know that he was right. His procedure works especially well for curing ROUGH surfaced cast iron vessels such as your Lodge cast iron skillet. Not a rocket science procedure maybe.....but factually based on real science non the less.
As I stated above patina development is a two part process. Part 1 involves the polymerization of the unsaturated oils/fats in the curing oil. Part 2 involves the thermal cracking of the oil/fat and actual carbon laydown into the matrix. These two patina developing mechanisms can take place independantly of each other or can occur almost at the same time........it just depends on the conditions at the time of the curing process. Factors affecting rates of patina development reactions include 1) concentration of unsaturated fats 2) concentration of saturated fats 3) temperature 4) pressure 5) pot metal metalurgy (catalyst affects) 6) Conradson carbon residue content of the curing oil or fat. It can get rather complicated (boring?) if I try to go into too many details. However, the seasoning process itself is not complicated at all if you follow good procedures.
Regarding Polymerization: Polymerization simply is a chemical reaction whereby molecules contained in unstable unsaturated (double bonded carbon atoms) oils or fats combine or crosslink with other molecules to form other more stable compounds with very different chemical and physical properties. Our goal in the curing process is to control these polymerization reactions in such a manner that they produce polymers with physical properties that are good for cooking purposes (i.e. a non-stick, hard, durable patina).
1 )The rate of these polymerization reactions are very much dependant on type of oil, curing temperature, and the chemical compositon of the metal surface. 2) The chemical and physical properties of the polymer formed is also very much dependant on type of oil, temperature, and metal surface. /p>
One example of a polymerized oil is the "STICKY" residue some people complain about in their cast iron pans. This is usually caused by coating cast iron with oil which is high in unsaturated fats (vegetable oils) and keeping the temperature rather low. A problem with this situation is that this type of polymer residue is also prone to further oxidation (because all of the double bonds have not been saturated). This means it can turn rancid as oxygen gets into the polymer matrix. Another unfortunate physical property of this type of patina is that it is totally worthless for non-stick cooking.
To properly cure cast iron we need to push the polymerization reactions beyond the "sticky" stage and more towards the "dryer" stage.........and that my friend requires the right amount of heat. Cooks complain they cannot remove sticky polymerized mess even with soaps and detergents. They cannot remove it because polymerized oily residue is a completely different product than that of the mother oil. Soaps/detergents will remove excess mother oil but will not remove the sticky polymers. To keep a cast iron pan from getting sticky.......don't use excess vegetable oil to coat that pan.......or use a more stable saturated fat like lard or crisco. Remember putting a thin layer of oil on cast iron to form a "protective coating" is one thing.....however, if you want to use that oil to "build patina"..........you must heat it.