A first-time owner of a cast iron skillet wrote to me the other day to ask, “Should I add oil to my skillet before or after heating it?”
As long-time readers of Home Cook World know, I love it when someone reaches out to me with a good question. One of the things I’ve found out through turning my replies into posts is that, more often than not, they’re not the only ones asking!
This is why, in this post, I’m going to give you my take on the topic. So… Do you heat your cast iron skillet before adding oil?
You can add cooking oil to your cast iron skillet before or after preheating it; it comes down to personal choice. While this matters for other types of cookware, it won’t make much of a difference with cast iron.
The owner’s manuals of non-stick frying pans, for example, will instruct you to drizzle some oil in them before preheating.
But that’s only because empty frying pans tend to reach excessively high heat on your stove, and, to avoid damage, polytetrafluoroethylene (PTFE) coatings shouldn’t be heated above 550°F.
Unlike their non-stick counterparts, cast iron skillets are incredibly sturdy. Cast iron as a material will only melt at temperatures of 2,200°F or higher, so this recommendation doesn’t really apply to it.
Whether you added the oil to your skillet before or after bringing it up to heat, the important thing is always to ensure it’s hot enough before you get cooking.
Otherwise, your food will come out oily and pale rather than crispy and well-browned.
The other thing you want to do to keep that from happening is not to overcrowd your skillet; adding or cooking too much food in it at once is a no-no as it lowers the temperature too much, too quickly.
This is also where most of my peers will tell you to use an instant-read thermometer to know when the oil in your pan is hot enough (and point you to some of the higher-end models at an online retailer your purchase of which they’ll get a commission from).
And, while I do the same thing on the posts where you’re looking for my picks, let’s be honest here: whipping out an instant-read thermometer whenever you cook is just not practical…
How to Tell If the Oil in Your Skillet is Hot Enough
To tell when the oil in your pan is hot enough, trust your senses.
When the oil in your frying pan starts to glisten and shimmer (sparkle and dance), this is usually a sign that it’s hot enough to cook with.
Butter is a different story. When you first add it to your pan, it starts to melt. But that doesn’t mean it’s ready. Before cooking with it, you want to wait until the bubbles to begin appearing and eventually stop forming.
Butter contains approximately 15% water. When you bring it up to heat, the water starts to evaporate. When fewer and fewer bubbles appear in your skillet, most of the water in the butter has evaporated—and the butter is most probably hot enough.
To learn more about using butter in your daily cooking, check out my whole post on the topic titled “The Home Cook’s Guide to Butter.”
Can You Preheat Cast Iron?
Is it okay to preheat cast iron skillets? There’s no right or wrong way to do this; here’s how I do it.
Cast iron has poor thermal conductivity. It’s only 1/3 as good at conducting heat as aluminum and 1/5 as good as copper. This is why cast iron skillets take time to get up to heat. But once they do, they distribute the heat evenly and are capable of holding on to it exceptionally well.
Heat your cast iron skillet for 2-3 minutes before you get cooking in it. Cooking works best when food comes into sudden contact with a hot cooking surface that makes it sizzle and steam. You can add oil before or after you’ve brought the skillet to heat; it won’t make much of a difference.
Why Is My Cooking Oil Smoking?
Ever been in the kitchen and had your cooking oil smoke? It’s probably because you’re using too high heat.
Be careful not to overheat the oil to the extent that it starts to emit bluish smoke; it will develop a bitter taste and form free radicals harmful to your health.
Last but not least, the smoke will build up in the form of soot the walls in your kitchen. This can be difficult to clean up (and, sooner or later, will require a new paint job).
All cooking oils have a smoke point, the threshold at which they stop to move around in your skillet and start to break down. This process is called oxidation and will cause an intense burning smell like what you might get if you left something on the stove for too long or used old oil.
Once it happens, there’s no turning back; you may have to replace the oil in your pan. As a general rule of thumb, you should always choose a cooking oil with a higher smoke point than the heat of the cooking method that you’re using for the recipe in question.
Below, I’ll give you my tips for how to always choose the right kind of cooking oil.
What Are the Best Oils for Cast Iron Cooking?
It turns out that our choice of oil is more important than most of us think. In fact, it can make our break our dish altogether.
When you’re searing steak or salmon fillet, use a high-heat cooking oil such as avocado, rice bran, safflower, or sunflower oil. All of these grocery-store oils will remain stable, even over high heat.
Delicate and tender oils and fats, like extra virgin olive oil or butter, should only be used for low- to medium-heat cooking. If you’re hearing this for the first time and are genuinely surprised by it, no wonder.
The selection of cooking oils is a topic that very few cookbook authors and television chefs talk about. Given how important it is to the taste of your food and its overall effect on your health, it often beats me why.
Can You Cook Without Oil?
Provided your cast iron skillet is well-seasoned, you can cook in it with or without cooking oil. The seasoning will keep food from sticking to the bottom.
From a technical perspective, you achieve two things by adding cooking oil to your frying pan, according to Dr. Stuart Farrimond, author of one of my favorite cooking books, The Science of Cooking.
“Oil carries flavor molecules and conducts heat efficiently to the surface of the food.” It also forms a lubricating layer between the food and metal that stops it from sticking and falling apart. In cast iron cooking, most of that second function is already performed by the seasoning.
The “seasoning” on a cast iron skillet is a thin patina of carbonated oil that keeps the bare iron from reacting to the oxygen in the air and moisture in your foods. It not only protects the vessel from corrosion and rust but also keeps food from sticking to the cooking surface.
In Conclusion
When cooking with cast iron, you can add oil before or after you’ve preheated your pan. I usually do the first, as it helps me identify when the oil is hot enough (and allows me to make sure that I’m not heating it above its smoke point).
