Stainless steel isn’t a good conductor of heat. And yet it’s great for making cookware out of. Here’s why.
The thermal conductivity of metals is measured in Watts per meter-Kelvin (W/m K). It’s a property that describes a metal’s ability to transfer heat from its hottest end to its coldest end. A low value means poor conductivity, a high value means excellent conductivity.
Suppose a metal has a thermal conductivity of 1 W/m K. This means that a 1-meter cube that’s made out of this metal will conduct heat from one end to the other at a rate of 1 Watt for every 1 degree change in temperature.
With a thermal conductivity of 14.4 W/m K, stainless steel is a poor conductor of heat. Nevertheless, it is used in the manufacture of cookware because stainless steel pans and pots are durable and dishwasher safe.
This sounds counterintuitive, I know. Especially when you consider that restaurateurs and chefs swear by stainless steel cookware, and some of the most expensive pans and pots in the department store are made out of this metal. (We will get to why in a minute.)
To understand how poorly stainless steel conducts heat, let’s compare it to the four other metals commonly used for making cookware: cast iron, carbon steel, aluminum, and copper.
- Compared to cast iron, which has a thermal conductivity of 52 W/m K, stainless steel conducts heat 3½ times worse;
- Compared to carbon steel, which has a thermal conductivity of 54 W/m K, stainless steel conducts heat 3½ times worse;
- Compared to aluminum, which has a thermal conductivity of 237 W/m K, stainless steel is 16½ times worse at conducting heat;
- Compared to copper, which has a thermal conductivity of 413 W/m K, stainless steel is 28½ times worse at conducting heat.
So why is some of the finest cookware made out of it?
Why Cookware Is Made Out of Stainless Steel
For starters, stainless steel is resistant to corrosion and rust. (The only other metal of which this can be said is aluminum.)
In terms of chemical makeup, stainless steel is an alloy of iron, carbon, chromium, and nickel. The carbon content makes the steel strong and robust. The nickel makes it foldable and bendable. Last but not least, the chromium gives it protection from the elements.
As a metal, stainless steel is inert. If you simmer something with canned tomatoes, vinegar, or wine, the acidity in the cooking liquid won’t react with the steel surface. Use a cast iron or carbon steel skillet, and dietary iron will leach into your food, imparting it with a strong metallic aftertaste.
Aluminum and copper are not only reactive, but toxic, particularly when ingested in large quantities. This is why all aluminum pans are hard-anodized or have a ceramic or non-stick coating. For the same reasons, copper pans are lined with tin, silver, or stainless steel (hence the expression “silver lining.”)
Let’s not forget that stainless steel is durable and dishwasher safe.
You are cooking on bare metal, so you can use utensils made of steel, flipping foods with metal spatulas and stirring sauces with metal spoons, and not have to worry about scratching the coating; there is no coating to scratch.
There are disadvantages to this, of course. Stainless steel frying surfaces are notoriously sticky; you need to add a dollop or two of cooking oil and preheat the pan long enough to keep foods like eggs or fish fillets from sticking.
You can load a stainless steel frying pan in the dishwasher without hesitation. As long as the handle is made of a durable material, it won’t discolor, corrode, or rust. I do most of my daily cooking with stainless steel and I wash all of my pans and pots in the dishwasher; they are still in mint condition.
Poor Thermal Conductivity Means Excellent Heat Retention
While an aluminum or copper pan will preheat in as little as 20-30 seconds, a stainless steel pan or pot will take 2-3, sometimes even 4-5 minutes to come up to temperature. For certain cooking methods, this can be an advantage.
Stainless steel has an excellent ability to retain heat. It lets go of heat as reluctantly as it absorbs it in the first place. The temperature of a stainless steel cooking vessel will not fluctuate as much when you put a cold steak or a new batch of fish fillets in it, so your food will brown better and cook faster.
This type of pans and pots perform superbly in cooking tasks that require high and steady heat, from searing to sautéing.
The Secret Is in the Construction
Though their name suggests otherwise, stainless steel pans and pots are made of a combination of metals, not just stainless steel.
To compensate for the poor conductivity of this metal, cookware manufacturers make the exterior of their cookware from stainless steel and bond the base—or, on well-constructed pans and pots, the entire core—with aluminum or copper.
Copper is the best heat conductor of all. Alas, it is also incredibly expensive. That’s why it’s found only in the most expensive pans and pots, usually hanging on the walls of celebrity chefs’ homes. Aluminum is affordable and, as far as cooking at home is concerned, just as good.
Now, there are two technologies for bonding steel to aluminum or copper.
Cheaper pans and pots comprise a stainless steel body with a thick, heavy aluminum or copper disc bonded to the underside on the bottom. The disc results in rapid and even heating on the frying surface, but not on the sides.
Mid-range and high-end pans and pots have a body that’s made of alternating metals pressed into the shape of a cooking vessel. Known as “cladding,” this technology ensures quick and even heating all around.
Generally, clad cookware can consist of three (tri-ply), five (five-ply), and seven (seven-ply) layers of metal. Tri-ply and five-ply frying pans are best for home cooking; seven-ply frying pans are overly expensive and intended first and foremost for professional chefs.
When to Buy Stainless Steel Cookware
Those brown bits and pieces of food that stick to the bottom of the frying pan during cooking? Instead of rinsing them down the drain, you can deglaze them to make the most delicious pan sauce. (As they say, it’s not a bug—it’s a feature.)
If you want an all-metal pan, but you don’t want to deal with the hassle of seasoning cast iron or carbon steel, stainless steel cookware is a great choice. You get all the benefits of cooking with metal with none of the complicated rituals for care and maintenance.
Stainless steel is the de-facto choice for home cooks who want to be able to clean their pans and pots in the dishwasher. Although ceramic and non-stick pans are often marketed as dishwasher-safe, the bolts and rivets on their handles are prone to corrosion and rust.