About IronSeason — cast iron seasoning guide calculator
Seasoning is not a coating painted onto cast iron, it is a thin layer of polymerised oil bonded to the iron itself. When oil is heated past its smoke point in a very thin film, it breaks down and links into a hard, dry layer that fills the microscopic pores of the metal. Repeated thin layers build a smooth, naturally non-stick surface that also protects the iron from rust. Thick layers do the opposite: they pool, stay gummy, flake off and attract dust. That single distinction explains most seasoning failures, and it is why IronSeason calculates a small, measured amount of oil and then tells you to wipe most of it away. The pan should look almost dry before it goes into the oven.
The amount of oil scales with pan size, because a larger cooking surface needs more oil to cover it, even though the layer stays paper-thin. IronSeason uses a simple rule of about 0.4 teaspoons per inch of diameter, so an 8-inch skillet needs about 3.2 teaspoons, a 10-inch skillet about 4 teaspoons, and a 12-inch skillet about 4.8 teaspoons, all before wiping. Those numbers are for the oil you rub on, not the oil that stays: after rubbing, wipe with a clean cloth or paper towel until no visible pools remain and the surface looks matte. If the pan looks shiny and wet, you have left too much oil on, and the result will be sticky rather than slick.
Oil choice matters because seasoning happens at or just above the oil's smoke point. Flaxseed oil, with a smoke point near 225 degrees Celsius, is popular for seasoning because it polymerises into a very hard layer, though it can be brittle and expensive. Grapeseed oil at about 216 degrees is a reliable all-rounder, widely available and less prone to flaking. Canola at about 204 degrees works well and is cheap, making it a sensible choice for a first seasoning. Shortening, at about 215 degrees, is the traditional choice in many American kitchens and gives a durable, forgiving layer. Avoid extra-virgin olive oil for oven seasoning: its low smoke point and strong flavour make it a poor choice, even though it is excellent for cooking in an already seasoned pan.
Preparation before the first layer is just as important as the oil. A new pan often arrives with a factory coating that should be washed off with hot water and a little soap, then dried completely, ideally on gentle heat, so no moisture remains. A rusty second-hand pan needs more work: scrub rust with salt, a chain-mail scrubber or fine steel wool, wash, dry immediately and season promptly before new rust forms. Never soak cast iron for hours, and never put it in a dishwasher, because prolonged water contact is exactly what seasoning protects against. Once the pan is clean and bone dry, the first thin layer can go on, and the pan should go into the oven upside down so any excess oil drips away rather than pooling.
The oven method is straightforward and repeatable. Heat the oven to the smoke-point temperature for your chosen oil, place the oiled pan upside down on the middle rack with a foil-lined tray below, and bake for one hour. Then switch the oven off and let the pan cool in the oven before handling it, because the layer hardens as it cools. Repeat the wipe, heat and cool cycle two more times for a total of three thin layers, and you will have a sound base seasoning. Ventilation matters: seasoning produces smoke, so open a window or switch on the extractor fan, and do not be alarmed by a light haze. If the pan comes out sticky, the layer was too thick; strip nothing, just cook with it and add thinner layers next time, or scrub and start again if stickiness is severe.
Daily cooking maintains seasoning better than any special ritual. Cook with fats, avoid long simmers of very acidic foods such as tomato sauce in a newly seasoned pan, and clean while the pan is still warm with hot water, a stiff brush and a little soap if needed. Modern soap does not strip polymerised seasoning, despite the old warning, though harsh detergents and soaking can damage it. Dry the pan on the stove over low heat, rub in a whisper of oil while it is warm, and store it dry. Eggs sticking slightly in the first weeks is normal: seasoning improves with use, especially with foods cooked in fat, and a pan that is used often will outperform a pan that is seasoned once and left in a cupboard.
Rust, flaking and a dull grey look are all fixable, and none of them means the pan is ruined. Surface rust can be scrubbed off, the pan dried and re-seasoned in the usual way. Flaking usually means layers were too thick or the pan was heated unevenly, and the remedy is to scrub loose flakes, wash, dry and rebuild with thin layers. A pan that looks dry and grey after cooking acidic food has usually lost only the top layer, not the whole seasoning, and a couple of stovetop seasoning rounds will restore it. The great virtue of cast iron is that it is almost impossible to destroy by normal cooking, and every mistake can be corrected with scrubbing, drying and thin oil.
Worked examples show how simple the calculation is. A 12-inch skillet needs 4.8 teaspoons of oil before wiping, heated at the smoke point of the chosen oil. A 10-inch skillet needs 4 teaspoons, and an 8-inch skillet needs 3.2 teaspoons. Enter your own pan size, choose an oil you already own, wipe thin, bake for an hour, cool, and repeat. Three patient thin layers beat one thick shortcut every time, and the pan you season properly today can cook breakfast for the next generation.
Stovetop seasoning is a useful companion to oven seasoning, especially for maintaining a pan between full oven sessions, and it follows the same thin-layer rule. Heat the pan gently on the stove, rub in a whisper of oil with a paper towel held by tongs, and keep heating until the oil just begins to smoke, then wipe again and let the pan cool. Repeat that cycle two or three times after cooking, and the surface will darken and smooth over weeks, without the smoke and time of a full oven session. Never leave a pan unattended on high heat with oil in it, and keep the extractor fan on, because smoking oil is unpleasant and can set off alarms. For daily cleaning, hot water and a stiff brush remove most food, and a short boil of water in the pan loosens stubborn residue without scrubbing away seasoning. Avoid harsh oven cleaners and self-cleaning oven cycles for stripping, unless you fully understand the fire risk, because most pans never need stripping at all. A pan that has been neglected can usually be rescued by washing, drying on heat, and three thin oven layers, and that rescue is part of why cast iron is handed down through families. The patina that builds over years is not dirt, it is the seasoning itself, dark, smooth and increasingly non-stick, and it tells the story of thousands of meals. Cook with the pan often, dry it promptly, oil it lightly, and it will outlast every non-stick pan you have ever owned, while improving with every breakfast, sear and roast.