Post by Glen Carman aka Delmonico on Sept 18, 2017 0:25:41 GMT -6
Cleaning, Seasoning and Care of Cast Iron Cookware
I will start with what is known as seasoning, perhaps one of the most misunderstood parts of cast iron cookware, this is the place where most fail, lack of a proper seasoning is where the majority of problems people have with cast iron come from. A true seasoning on our cookware is a thin layer of carbonized/polymerized eatable oils/fats that have had all the volatile substances burned off, leaving only the carbon behind and forming long chain molecules. If that sounds complicated, it’s not, it is easy to do and I will come back to that simple process in a bit, but first we need to have our cookware prepped to accept the seasoning.
Preparing Cast Iron for Seasoning
Our cookware we need to get ready to use can be newly made or it can be new to us, but used by someone else in the past, or even something we have owned for a while, but are not happy with how it works due to being poorly seasoned.
Most of the new cast iron sold today is what is called pre-seasoned, it is the easiest to work with, wash it with soap and water, dry it, add some oil, get the oil hot, add a couple eggs and then fry them, if it works fine, it is good to go, it is now ready for cleaning and care, if not, the factory did not get it seasoned well, but I’ll tell you how to fix that in a bit, start a pile for cast iron needing seasoned.
I will note before going further that when you get cast iron clean and down to the bare metal and dried, you will sometimes have a bit of red powdery rust on the surface, that is fine, no harm, no foul, the seasoning process will take care of it.
New but not pre-seasoned will have some sort of oil or wax to prevent it from rusting, often these can be removed with just soap, hot water and a good scrub pad, rinse well and dry it over the stove burner to remove all the moisture, look to see if it has that nice grey color of bare iron, you may have a fine layer of red oxide known as rust, but that is no problem, set the piece aside in the pile of needing seasoned and we’ll get to it after we get our used pieces ready.
Used cast iron often causes the most controversy as to how to get it ready for use, many say if the piece looks good and is well seasoned just use it, I don’t, I prefer to strip it and re-season it, others may not, it’s just what I prefer. As for the method used, it’s like the old saying, “and that is when the fight began.” There are several methods; all will work if they are used properly, they all can cause trouble if used improperly, and the methods I know of can be heat, chemical, mechanical, electrolysis or even a combination of all of them. Before using any of these methods, like new pieces, I like to wash the piece with hot soap, water and the scrub pad to remove all the oils.
To me, the easiest is heat, although when it is discussed it seems to be the most controversial method with many saying you will ruin the piece, well you can, over heat it and/or heat it very unevenly and you can warp it, you can crack it or form an oxide layer often called red scale that makes it hard to season.(the red scale can be removed by mechanical methods because it’s just on the surface, hand sand with 120 -150 grit sandpaper till clean and shiny and don’t do it again.) Use heat in a sensible manner and there is no problem, but I will add this disclaimer I would hesitate using it on a really old valuable piece, if you do over heat it and warp or crack it, then that piece is lost forever because they are no longer made, practice on lesser pieces.
As for cleaning it with heat, I most often just take the piece or pieces with me to one of my camps and in the evening when the cooking is done (and before it gets dark, the time people want to sit around the fire) I just let the fire burn down to low coals spread out evenly and place the piece or pieces on top of the coals and let the crud burn off, removing it when clean and before the piece gets that red glow to it. I then set the piece aside to cool then take it home and finish it most times.
Others use a self-cleaning oven, very simple and easy, it might smoke the house up some, I have used it in the past but no longer have that type of stove. Others use a outside gas grill and that keeps the smoke out of the house, no matter what the method of providing heat, the goal is to clean it only and by not turning it red hot or beyond and heating it evenly it has worked fine for me for a lot of years. After it has cooled, I put it in the sink (or if too big for the sink I use our bath tub) and use warm water and dish soap on it and scrub it up well removing all the burnt material with a stainless steel pot scrubber, then dry it on the stove and it is ready for our pile that needs seasoned.
Chemical methods most often involve either an alkaline substance or an acid substance to remove rust and built up layers, the alkaline substance most often being lye, (sodium hydroxide or potassium hydroxide solution) it is often used in drain cleaners and oven cleaners, and it is caustic so some care has to be used with it. One method often used is to simply buy spray on oven cleaner and to use it on the piece then put it in a garbage bag for several hours or even several days, rinse, scrub well with soap and water and see if all residue has been removed, if not, recoat and let is soak again.
The lye method involves adding 1 pound of lye to 5 gallons of water (make sure the lye is added to the water and not the water to the lye) and soaking the cast iron in this, the cast iron can stay in it a long period with out harm. One must remember lye is caustic and one must keep it from contacting the skin and is best done in an area where children and pets can’t come in contact with it.
Lye does a good job of removing the old build up, but is not that good for removing rust, many recommend neutralizing the lye with vinegar after cleaning, but rinsing well should remove all the lye, one can do this to make yourself feel good, if there is lye left, there will be a bit of bubbling when the vinegar is added from the Carbon dioxide being formed as the lye is neutralized.
When using the acid method one of three acids are used, one being acetic acid the acid found in vinegar, citric acid found in citric fruits as well as molasses and phosphoric acid, which is often used as metal prep for cleaning new metal before painting, but is also used in soda pop to give it that bite, Coca Cola having what is said to be the highest percent.
Vinegar can be used straight or diluted, and any type can be used, I use white vinegar because most times it’s cheaper and I use the cheap store brand. Most vinegar is about 5% acidity no matter the brand. The method recommended by many for a vinegar bath is a non-metal container big enough for the piece or pieces and fill it with ½ vinegar/1/2 water and submerge the piece in and let it soak for a few hours, remove from the bath, scrub as before and resoak if needed. I myself just use our bath tub since we also have a shower, it is not unusual to have cast iron being cleaned in my tub and it works great.
The citric acid method seems to most often use molasses as a cheap source of this acid, the recommended amount being 1 part molasses to 9 parts water, this method is said to take 2-4 weeks by those who use it and the animal supplement type found at farm stores is the cheapest. I myself have never tried this, but I’m relating it because some seem to like the method, to me it’s too slow.
The phosphoric acid is perhaps best used as Coca-Cola I have used this in the past as a cleaner for small steel and iron parts, having also used the higher strength metal prep in the past; I don’t recommend it metal prep for home use. The Coca-Cola works well to remove rust but making a vinegar bath although perhaps slower, is cheaper than the Coca-Cola by far.
Mechanical can be as simple as a good scrub pad, sand paper, steel wool or other similar items, or it can involve using compressed air to force an abrasive material under pressure, this is called blasting, the abrasive can bee sand, steel shot, ground corn cobs or walnut shell or baking soda. The baking soda uses the finest grit and is what I recommend if having pieces blasted. The other can leave a very rough surface, depending on the coarseness of the grit, the pressure it’s blasted as well as the skill of the operator using the equipment. Soda blasting is used for a lot of delicate restoration work so it will be fine on cast iron although it will cost more than the do it yourself methods.
The electrolysis method uses an electrical currant to remove the rust, it is a process similar to plating with chrome or other metals, but the process is reversed. The iron from the rust is deposited on another iron rod rather than the metal from a rod being deposited on the piece as in plating; in fact this method is used in restoration work to remove plating before prepping and replating.
The rusty iron and the so called sacrificial rod are immersed in a solution of washing soda (Sodium carbonate) available at most any grocery store along with the laundry detergent at a ratio of 1-2 tablespoons per gallon of water. The sacrificial rod and the cast iron piece are hung in a non-metallic container so they are fully immersed. A manual (not automatic) battery charger is hooked up with the negative (black) to the piece to be cleaned and the positive (red) to the sacrificial rod and the current turned on, the rust them flows to the sacrificial rod and the whole process only takes a few hours. A battery can be added to the circuit if the battery charger is not a manual one, the current to the tank needs to come from the battery and the battery charger keeps the battery from being drained. (As anytime working around water and electricity one needs to be very careful, the washing soda is what is called an electrolyte and makes the water more conductive to electricity.)
As before, clean the piece with soap, water and a scrub pad, dry with heat and examine to see if you have reached the bare iron. If it is done, also add it to our pile.
Seasoning Cast Iron
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.
Cleaning Seasoned Cast Iron
Once the cast iron is seasoned and is used to cook with, we come to having to properly clean it after use, this is another place where the methods differ between people, I have seen long internet discussions on this that have almost turned hostile, most seem to think the seasoning on cast iron is delicate, which as we discussed above, it is not if done properly.
I will state right now those words that cause all kinds of problems in discussions on cleaning cast iron, “I am not afraid to use dish soap in my cast iron” in fact if something really greasy has been cooked in it like a pork roast, I will use it to help get rid of the excess grease which can turn rancid. I also am not afraid to use scrubbing pads such as the green and brown 3M type or even stainless steel ones. What are not hard to remove are any oils that are on the surface of the seasoning, these may have been put on to preserve the piece from rust or it may be left over from cooking. I often cook large meals that use 10-12 dutch ovens and most times I am doing everything on my own, it just makes things easier and quicker and since there is truly no harm in doing it, why make things more difficult than it needs to be?
Many times I have been told to not use soap because the pores in the cast iron will soak up the soap and anything cooked in it will have soap in it. Well the surface of the cast iron has some microscopic pores in it, true, although the carbonized oils do fill them, but what is more important is if these pores are not fully filled with the seasoning any soap that goes in is so minute as to not be noticed, plus it will rinse out just fine, the cast iron is not as porous as many think.
Another item to use for those really tough to clean messes is washing soda (Sodium carbonate which is not the same as baking soda or Sodium Bicarbonate) available in the same area as laundry detergent in most stores. This is not soap, but it does soften the water so it cleans better than plain water, a lot of the water in wells where I cook is very hard and this just helps my dish soap work better.
One item often said to be bad on cast iron is the dish washer, I do not having one of these devices so I can say I have never tried one with cast iron, but rather than the dish washer itself being the problem, my thoughts are it’s the piece sitting wet in that damp environment that causes the problem, wash a cast iron piece with any method using water and let it slowly dry in a damp environment and you will get rusting, not anything you can’t fix, but it will rust.
Care of Cast Iron
Once the cast iron is clean no matter what method you use, it needs thoroughly dried, it can be dried with a towel if desired, but it still should be heated up to drive any moisture out, then a light coat of oil put on to prevent rust. At home a stove burner can be used, in camp the fire, it just needs heated up enough to remove any trace of the water, often on hot days I save time and trouble by leaving the lids off with the oven in the sun, at 90 F or more they get too hot to touch in a short time and are dry very quickly.
After the piece is heated, it needs wiped with a very thin coat of oil, most do it while still warm, this makes the oil flow a little better and reach every corner. Just like seasoning this coat should be very thin, and if possible, a non-drying oil is best. Which bring us to another term that need explained.
Oils are classed as non-drying, semi-drying and drying, in other words some oils will oxidize to the point they will form a dry film, in other words, add pigments and you have oil paints, not really something we want on out cast iron cook-war, most, (but not all) cooking oils are semi-drying or non-drying. Semi-drying oils often have driers added to make them drying oils as well as drying oils having them added to cause faster drying. Where to class the oils is determined by an analytical process that determines how much iodine a specific amount of the oil will absorb, no need to get any deeper here, but for our use all we need to know is this is called Iodine Value and number of the iodine value determines where it is classed.
Iodine values of oils over 130 are considered drying oils and a couple common ones are:
Tung Oil at around 165-175
Linseed/flax seed oil at 135-180
These are true drying oils in their natural state, although Tung oil is not used in cooking, linseed oil is, but under its other name, Flax Seed Oil, when bought as linseed oil or boiled linseed oil it is not intended for human consumption, the boiled has additional products added to speed up drying. Other common oils ride the line on if they are drying oils or semi-drying oils, depending on the particular lot of oil, a value of 115 to 130 are considered semi-drying oils, these can include:
Sunflower at 125-145
Grape seed at 125-145
Walnut at 120-140
Soy Bean at 120-135
Wheat Germ Oil at 115-135
Canola Oil at 110-130
Corn Oil at 110-130
Non-drying oils are ones with an iodine value below 115:
Cotton Seed at 100-115
Rice Bran Oil at 100-110
Olive Oil at 80-90
Lard at 60-70
Beef Tallow at 50-60
Palm Oil at 45-60
Palm Kernel Oil at 15-20
Coconut Oil at 5-15
(Values are based on several sources and averaged.)
(Palm Oil and Palm Kernel Oil are different oils from different palms)
Non-drying oils are the best for wiping, because they won’t get gummy if it is put on a little thick and don’t risk getting rancid like others.
I have always preferred olive oil for wiping a piece that will be stored over a couple of weeks, just a thin layer put on with a rag works well, for short term I often use lard, this is one pieces that get used often, my most used kitchen pieces and my camp ovens when cleaning up to go home from a trip. Then for storage I clean them up and use olive oil on them.
I see mineral oil recommended at times for both seasoning and preserving cast iron; on the plus side it rates a 0 on the Iodine Value so it has no chance of getting gummy. But to me the down side is it’s a refined petroleum distillate and although there is a food grade mineral oil, it is intended more as a lubricant for food processing machinery, its use in food products is very restricted by law. One of the medical uses of mineral oil is a laxative and there are many cautions on its uses in that field, I just prefer to stay away from it, although some who use it swear by it.
When it is all said and done, just about any food grade oil will work for preserving our cast iron after cleaning, but we can see the true non-drying oils are more forgiving when you get it on a little thick and animal fats and the semi-drying oils do run a risk of turning rancid, to me it just makes sense to stick with a vegetable oil that always falls under the non-drying oil status. Of these for me at least the olive oil gets the go, it is easy to find at almost any grocery store, it is something I generally keep in the groceries because it is correct to the 19th Century and has some uses for me in cooking. To vary from this requires I buy another item and in camp it means I have an extra item I have to take to camp; I just prefer to keep things as simple as possible.
I will start with what is known as seasoning, perhaps one of the most misunderstood parts of cast iron cookware, this is the place where most fail, lack of a proper seasoning is where the majority of problems people have with cast iron come from. A true seasoning on our cookware is a thin layer of carbonized/polymerized eatable oils/fats that have had all the volatile substances burned off, leaving only the carbon behind and forming long chain molecules. If that sounds complicated, it’s not, it is easy to do and I will come back to that simple process in a bit, but first we need to have our cookware prepped to accept the seasoning.
Preparing Cast Iron for Seasoning
Our cookware we need to get ready to use can be newly made or it can be new to us, but used by someone else in the past, or even something we have owned for a while, but are not happy with how it works due to being poorly seasoned.
Most of the new cast iron sold today is what is called pre-seasoned, it is the easiest to work with, wash it with soap and water, dry it, add some oil, get the oil hot, add a couple eggs and then fry them, if it works fine, it is good to go, it is now ready for cleaning and care, if not, the factory did not get it seasoned well, but I’ll tell you how to fix that in a bit, start a pile for cast iron needing seasoned.
I will note before going further that when you get cast iron clean and down to the bare metal and dried, you will sometimes have a bit of red powdery rust on the surface, that is fine, no harm, no foul, the seasoning process will take care of it.
New but not pre-seasoned will have some sort of oil or wax to prevent it from rusting, often these can be removed with just soap, hot water and a good scrub pad, rinse well and dry it over the stove burner to remove all the moisture, look to see if it has that nice grey color of bare iron, you may have a fine layer of red oxide known as rust, but that is no problem, set the piece aside in the pile of needing seasoned and we’ll get to it after we get our used pieces ready.
Used cast iron often causes the most controversy as to how to get it ready for use, many say if the piece looks good and is well seasoned just use it, I don’t, I prefer to strip it and re-season it, others may not, it’s just what I prefer. As for the method used, it’s like the old saying, “and that is when the fight began.” There are several methods; all will work if they are used properly, they all can cause trouble if used improperly, and the methods I know of can be heat, chemical, mechanical, electrolysis or even a combination of all of them. Before using any of these methods, like new pieces, I like to wash the piece with hot soap, water and the scrub pad to remove all the oils.
To me, the easiest is heat, although when it is discussed it seems to be the most controversial method with many saying you will ruin the piece, well you can, over heat it and/or heat it very unevenly and you can warp it, you can crack it or form an oxide layer often called red scale that makes it hard to season.(the red scale can be removed by mechanical methods because it’s just on the surface, hand sand with 120 -150 grit sandpaper till clean and shiny and don’t do it again.) Use heat in a sensible manner and there is no problem, but I will add this disclaimer I would hesitate using it on a really old valuable piece, if you do over heat it and warp or crack it, then that piece is lost forever because they are no longer made, practice on lesser pieces.
As for cleaning it with heat, I most often just take the piece or pieces with me to one of my camps and in the evening when the cooking is done (and before it gets dark, the time people want to sit around the fire) I just let the fire burn down to low coals spread out evenly and place the piece or pieces on top of the coals and let the crud burn off, removing it when clean and before the piece gets that red glow to it. I then set the piece aside to cool then take it home and finish it most times.
Others use a self-cleaning oven, very simple and easy, it might smoke the house up some, I have used it in the past but no longer have that type of stove. Others use a outside gas grill and that keeps the smoke out of the house, no matter what the method of providing heat, the goal is to clean it only and by not turning it red hot or beyond and heating it evenly it has worked fine for me for a lot of years. After it has cooled, I put it in the sink (or if too big for the sink I use our bath tub) and use warm water and dish soap on it and scrub it up well removing all the burnt material with a stainless steel pot scrubber, then dry it on the stove and it is ready for our pile that needs seasoned.
Chemical methods most often involve either an alkaline substance or an acid substance to remove rust and built up layers, the alkaline substance most often being lye, (sodium hydroxide or potassium hydroxide solution) it is often used in drain cleaners and oven cleaners, and it is caustic so some care has to be used with it. One method often used is to simply buy spray on oven cleaner and to use it on the piece then put it in a garbage bag for several hours or even several days, rinse, scrub well with soap and water and see if all residue has been removed, if not, recoat and let is soak again.
The lye method involves adding 1 pound of lye to 5 gallons of water (make sure the lye is added to the water and not the water to the lye) and soaking the cast iron in this, the cast iron can stay in it a long period with out harm. One must remember lye is caustic and one must keep it from contacting the skin and is best done in an area where children and pets can’t come in contact with it.
Lye does a good job of removing the old build up, but is not that good for removing rust, many recommend neutralizing the lye with vinegar after cleaning, but rinsing well should remove all the lye, one can do this to make yourself feel good, if there is lye left, there will be a bit of bubbling when the vinegar is added from the Carbon dioxide being formed as the lye is neutralized.
When using the acid method one of three acids are used, one being acetic acid the acid found in vinegar, citric acid found in citric fruits as well as molasses and phosphoric acid, which is often used as metal prep for cleaning new metal before painting, but is also used in soda pop to give it that bite, Coca Cola having what is said to be the highest percent.
Vinegar can be used straight or diluted, and any type can be used, I use white vinegar because most times it’s cheaper and I use the cheap store brand. Most vinegar is about 5% acidity no matter the brand. The method recommended by many for a vinegar bath is a non-metal container big enough for the piece or pieces and fill it with ½ vinegar/1/2 water and submerge the piece in and let it soak for a few hours, remove from the bath, scrub as before and resoak if needed. I myself just use our bath tub since we also have a shower, it is not unusual to have cast iron being cleaned in my tub and it works great.
The citric acid method seems to most often use molasses as a cheap source of this acid, the recommended amount being 1 part molasses to 9 parts water, this method is said to take 2-4 weeks by those who use it and the animal supplement type found at farm stores is the cheapest. I myself have never tried this, but I’m relating it because some seem to like the method, to me it’s too slow.
The phosphoric acid is perhaps best used as Coca-Cola I have used this in the past as a cleaner for small steel and iron parts, having also used the higher strength metal prep in the past; I don’t recommend it metal prep for home use. The Coca-Cola works well to remove rust but making a vinegar bath although perhaps slower, is cheaper than the Coca-Cola by far.
Mechanical can be as simple as a good scrub pad, sand paper, steel wool or other similar items, or it can involve using compressed air to force an abrasive material under pressure, this is called blasting, the abrasive can bee sand, steel shot, ground corn cobs or walnut shell or baking soda. The baking soda uses the finest grit and is what I recommend if having pieces blasted. The other can leave a very rough surface, depending on the coarseness of the grit, the pressure it’s blasted as well as the skill of the operator using the equipment. Soda blasting is used for a lot of delicate restoration work so it will be fine on cast iron although it will cost more than the do it yourself methods.
The electrolysis method uses an electrical currant to remove the rust, it is a process similar to plating with chrome or other metals, but the process is reversed. The iron from the rust is deposited on another iron rod rather than the metal from a rod being deposited on the piece as in plating; in fact this method is used in restoration work to remove plating before prepping and replating.
The rusty iron and the so called sacrificial rod are immersed in a solution of washing soda (Sodium carbonate) available at most any grocery store along with the laundry detergent at a ratio of 1-2 tablespoons per gallon of water. The sacrificial rod and the cast iron piece are hung in a non-metallic container so they are fully immersed. A manual (not automatic) battery charger is hooked up with the negative (black) to the piece to be cleaned and the positive (red) to the sacrificial rod and the current turned on, the rust them flows to the sacrificial rod and the whole process only takes a few hours. A battery can be added to the circuit if the battery charger is not a manual one, the current to the tank needs to come from the battery and the battery charger keeps the battery from being drained. (As anytime working around water and electricity one needs to be very careful, the washing soda is what is called an electrolyte and makes the water more conductive to electricity.)
As before, clean the piece with soap, water and a scrub pad, dry with heat and examine to see if you have reached the bare iron. If it is done, also add it to our pile.
Seasoning Cast Iron
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.
Cleaning Seasoned Cast Iron
Once the cast iron is seasoned and is used to cook with, we come to having to properly clean it after use, this is another place where the methods differ between people, I have seen long internet discussions on this that have almost turned hostile, most seem to think the seasoning on cast iron is delicate, which as we discussed above, it is not if done properly.
I will state right now those words that cause all kinds of problems in discussions on cleaning cast iron, “I am not afraid to use dish soap in my cast iron” in fact if something really greasy has been cooked in it like a pork roast, I will use it to help get rid of the excess grease which can turn rancid. I also am not afraid to use scrubbing pads such as the green and brown 3M type or even stainless steel ones. What are not hard to remove are any oils that are on the surface of the seasoning, these may have been put on to preserve the piece from rust or it may be left over from cooking. I often cook large meals that use 10-12 dutch ovens and most times I am doing everything on my own, it just makes things easier and quicker and since there is truly no harm in doing it, why make things more difficult than it needs to be?
Many times I have been told to not use soap because the pores in the cast iron will soak up the soap and anything cooked in it will have soap in it. Well the surface of the cast iron has some microscopic pores in it, true, although the carbonized oils do fill them, but what is more important is if these pores are not fully filled with the seasoning any soap that goes in is so minute as to not be noticed, plus it will rinse out just fine, the cast iron is not as porous as many think.
Another item to use for those really tough to clean messes is washing soda (Sodium carbonate which is not the same as baking soda or Sodium Bicarbonate) available in the same area as laundry detergent in most stores. This is not soap, but it does soften the water so it cleans better than plain water, a lot of the water in wells where I cook is very hard and this just helps my dish soap work better.
One item often said to be bad on cast iron is the dish washer, I do not having one of these devices so I can say I have never tried one with cast iron, but rather than the dish washer itself being the problem, my thoughts are it’s the piece sitting wet in that damp environment that causes the problem, wash a cast iron piece with any method using water and let it slowly dry in a damp environment and you will get rusting, not anything you can’t fix, but it will rust.
Care of Cast Iron
Once the cast iron is clean no matter what method you use, it needs thoroughly dried, it can be dried with a towel if desired, but it still should be heated up to drive any moisture out, then a light coat of oil put on to prevent rust. At home a stove burner can be used, in camp the fire, it just needs heated up enough to remove any trace of the water, often on hot days I save time and trouble by leaving the lids off with the oven in the sun, at 90 F or more they get too hot to touch in a short time and are dry very quickly.
After the piece is heated, it needs wiped with a very thin coat of oil, most do it while still warm, this makes the oil flow a little better and reach every corner. Just like seasoning this coat should be very thin, and if possible, a non-drying oil is best. Which bring us to another term that need explained.
Oils are classed as non-drying, semi-drying and drying, in other words some oils will oxidize to the point they will form a dry film, in other words, add pigments and you have oil paints, not really something we want on out cast iron cook-war, most, (but not all) cooking oils are semi-drying or non-drying. Semi-drying oils often have driers added to make them drying oils as well as drying oils having them added to cause faster drying. Where to class the oils is determined by an analytical process that determines how much iodine a specific amount of the oil will absorb, no need to get any deeper here, but for our use all we need to know is this is called Iodine Value and number of the iodine value determines where it is classed.
Iodine values of oils over 130 are considered drying oils and a couple common ones are:
Tung Oil at around 165-175
Linseed/flax seed oil at 135-180
These are true drying oils in their natural state, although Tung oil is not used in cooking, linseed oil is, but under its other name, Flax Seed Oil, when bought as linseed oil or boiled linseed oil it is not intended for human consumption, the boiled has additional products added to speed up drying. Other common oils ride the line on if they are drying oils or semi-drying oils, depending on the particular lot of oil, a value of 115 to 130 are considered semi-drying oils, these can include:
Sunflower at 125-145
Grape seed at 125-145
Walnut at 120-140
Soy Bean at 120-135
Wheat Germ Oil at 115-135
Canola Oil at 110-130
Corn Oil at 110-130
Non-drying oils are ones with an iodine value below 115:
Cotton Seed at 100-115
Rice Bran Oil at 100-110
Olive Oil at 80-90
Lard at 60-70
Beef Tallow at 50-60
Palm Oil at 45-60
Palm Kernel Oil at 15-20
Coconut Oil at 5-15
(Values are based on several sources and averaged.)
(Palm Oil and Palm Kernel Oil are different oils from different palms)
Non-drying oils are the best for wiping, because they won’t get gummy if it is put on a little thick and don’t risk getting rancid like others.
I have always preferred olive oil for wiping a piece that will be stored over a couple of weeks, just a thin layer put on with a rag works well, for short term I often use lard, this is one pieces that get used often, my most used kitchen pieces and my camp ovens when cleaning up to go home from a trip. Then for storage I clean them up and use olive oil on them.
I see mineral oil recommended at times for both seasoning and preserving cast iron; on the plus side it rates a 0 on the Iodine Value so it has no chance of getting gummy. But to me the down side is it’s a refined petroleum distillate and although there is a food grade mineral oil, it is intended more as a lubricant for food processing machinery, its use in food products is very restricted by law. One of the medical uses of mineral oil is a laxative and there are many cautions on its uses in that field, I just prefer to stay away from it, although some who use it swear by it.
When it is all said and done, just about any food grade oil will work for preserving our cast iron after cleaning, but we can see the true non-drying oils are more forgiving when you get it on a little thick and animal fats and the semi-drying oils do run a risk of turning rancid, to me it just makes sense to stick with a vegetable oil that always falls under the non-drying oil status. Of these for me at least the olive oil gets the go, it is easy to find at almost any grocery store, it is something I generally keep in the groceries because it is correct to the 19th Century and has some uses for me in cooking. To vary from this requires I buy another item and in camp it means I have an extra item I have to take to camp; I just prefer to keep things as simple as possible.
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