Which Metal Is Best for Deep Frying? (Science-Backed Guide)

Published Categorized as Kitchen
Food deep frying in a potWirestock /Depositphotos

When you reach for the right kind of saucepan or pot in your cabinets, deep frying becomes easy. Here’s what you need to know.

Everyone loves deep-fried food, and for good reason. When food is completely submerged and thoroughly cooked in hot oil, a crispy, golden-brown crust forms on the exterior as the interior remains juicy and tender.

To prep for deep frying, reach for a saucepan, a large pot, or a hefty Dutch oven in your cabinets. Fill it with cooking oil, turn the heat to medium, and preheat for 10 minutes. (It is crucial to operate the heat dial prudently: If you go too low, the crust won’t crisp and will come out soggy. Go too high, and it will

While waiting for the oil to get hot enough to cook in, use the time to cut up the food into portion-sized pieces for even cooking. Season each piece generously with fine salt and pepper. Right before cooking, coat each piece with flour, breadcrumbs, or batter, be it beer batter or tempura.

What does a simmer look like?
What does a simmer look like?

Cook your food in batches and don’t overcrowd your vessel with too many food items at once. Each time you submerge a food item into the hot oil, the temperature of the oil will drop temporarily and it will take a while to recover.

You know that the food is done when it becomes crispy and golden brown on the outside. When in doubt, take a piece out read its internal temperature with a meat thermometer.

Beef, pork, and lamb is cooked when the inside of the meat has reached 145°F (63°C). Poultry, on the other hand, is safe to eat at 160°F (71°C).

The Best Cooking Vessels for Deep Frying

For crispy and golden-brown food, the oil should recover its temperature as soon as possible after you’ve added a new batch of food to the pan or pot. By and large, this depends on the amount of food you prepare at once and the type of cookware you use.

You’re here, so let’s talk in more technical terms about the latter:

The best cooking vessels for deep frying are a deep skillet or a Dutch oven made of cast iron (bare or enameled). Alternatively, a saucepan or large pot made of clad stainless steel with an aluminum or copper core will also do.

If you’re serious about cookware—and you happen to have all of these in your collection—reach for the cooking vessel with the heaviest bottom and the thickest walls; the one that feels heaviest to the hand when you lift it.

Such a cooking vessel will take a long time to get up to heat. But once it does, it will be as reluctant to let go of that heat as it was to accumulate it in the first place. This means that it will act as a steady source of heat, heating the cooking oil uniformly, even as the temperature of the oil fluctuates between batches.

To minimize splatter and spillage, choose a cooking vessel capable of holding twice the amount of fat or oil you need to use for the recipe in question.

What Makes Cast Iron and Stainless Steel Good for Deep Frying

The reasons why cast iron and stainless steel are such good choices for deep frying come down to two properties: thermal conductivity and heat capacity.

Thermal conductivity is the ability of a metal to conduct heat. When we say that a metal is a good conductor of heat, this means it heats up and cools down quickly. Conversely, poor conductors of heat take a long time to heat up and just as long to cool down.

The thermal conductivity of stainless steel and cast iron is, respectively, 14.4 Watts per meter-Kelvin (W/mK) and 52 W/mK. Compared to aluminum and copper, whose thermal conductivity is 237 W/mK and 413 W/mK, they are generally poor conductors of heat.

This is the main reason why copper pans and pots respond to changes in the heat dial almost instantaneously, aluminum pans and pots take 20-30 seconds to heat up or cool down, whereas cast iron and stainless steel pans and pots “take forever” to respond.

Lack of responsiveness is undesirable when you’re making cream sauce or risotto, and you need to quickly adjust the temperature to prevent the cream from curdling or the rice from burning.

Ironically, that lack of responsiveness is precisely what you are looking for when you are deep-frying foods because it helps you even out the temperature fluctuations of the oil as much as physically possible.

Heat capacity is the ability of a metal to store energy in the form of heat. (Suppose your cast iron cooking vessel was a battery. Its heat capacity would be its battery life.)

Heat capacity is a function of a metal’s specific heat, the amount of heat that’s needed to warm a pound of that metal, and its density, or how heavy the metal is relative to how much space it takes up.

The specific heat of aluminum is 910 Joule per Kelvin per kilogram, but its density is only 2,600 kilograms per cubic meter. In comparison, the specific heat of cast iron is 460 J/(kg K), but its density is 7,900 kg/m3. Stainless steel has a specific heat of 500 J(kg K) and a density of 7,500 kg/m3.

MetalSpecific HeatDensityCapacity
Aluminum910 J/(kg K)2,600 kg/m32.36
Stainless steel500 J/(kg K)7,500 kg/m33.75
Cast iron460 J/(kg K)7,900 kg/m33.63
Copper390 J/(kg K)8,900 kg/m33.47

Multiply specific heat and density for each metal and divide by a million to get rid of the excess zeros, and you get the following ratios for heat capacity: 2.36 for aluminum, 3.63 for cast iron, and 3.75 for stainless steel.

(Since stainless steel cookware has a core of aluminum or copper, the end heat capacity of a stainless steel cooking vessel will be lower than that of a cast iron one.)

When deep-frying foods, you want a metal with a high heat capacity.

That way, the metal accumulates plenty of heat and heats your cooking oil steady, even as the thermostat on your electric stove switches the coils or radiant panels on and off. This also evens out minor fluctuations in the temperature of gas burners.

Together, poor thermal conductivity and high heat capacity make for an excellent cooking vessel for deep frying. And no other cookware matches this description as well as cast iron does.

By Jim Stonos

When Jim isn't in the kitchen, he is usually spending time with family and friends, and working with the HCW editorial team to answer the questions he used to ask himself back when he was learning the ropes of cooking.

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