Mad About Science: Cast Iron

By Brenden Bobby
Reader Columnist

Nothing beats the sizzle of a steak on a cast iron pan. Dense, seasoned metal bringing perfectly even heat and a flawless sear to the outside of your filet is a thing of real beauty. If you just so happen to prefer sautéed vegetables to meat, I won’t judge… much.

There’s no denying the utility of culinary cast iron, but what makes it so special and different from regular cookware? Steel is steel, right?

Courtesy photo

Metallurgy is kind of like baking with metal — precise configurations of ingredients, temperatures and time exposed to heat can create wildly different results from item to item. In the case of most cast iron, it has a carbon content of up to 4% (which is high) that produces unique results well-suited to specific functions. In 2025, one of the most widely used applications of cast iron is for cookware, owing to its phenomenal ability to hold and retain heat evenly across its surface. Caring for cast iron cookware comes with its own unique set of challenges you don’t have to worry about with ceramic and nonstick metal cookware.

Adding various elements to pig iron (that is, the intermediate product of iron ore smelting used to make steel), carbon and silicon during the smelting process can drastically alter the final product. Sulphur can make the metal harder, but more prone to cracking. Adding chromium or nickel can help counteract this by making the metal harder, but also less brittle.

The production of cast iron was believed to have started in China, sometime during the fifth century B.C.E. Cast iron is not well suited to creating very sharp objects that will be subjected to heavy impact forces, such as arrowheads, spears or swords. Instead, it was used for things like ploughs, pagodas and larger, heavier weapons. Knowledge of cast iron blacksmithing has also been observed in central Africa in the Congo around this time. The knowledge of how to create cast iron was likely brought west from China through roads that supported the silk trade. Cast iron production in Europe was believed to have started sometime in the 13th century C.E.

Later, cast iron and wrought iron both featured heavily in Victorian-era decoration in England, particularly for fireplace tools and decoration. Cast iron pots were frequently used throughout Asia as a form of food storage, and cast iron pots were a must-have for many people throughout history. 

Personal stoves were rare until the 19th century, as hearths were a much more common form of heating and cooking for communal and individual homes. Cast iron’s ability to retain and evenly distribute heat made it a perfect tool for cooking large quantities of food over a hearth. Its durability and reliability made it a staple throughout the American West in the 1800s.

However, cast iron cookware faded from widespread use as newer forms of cookware entered the market as more advanced technology and metallurgical techniques came to prominence. Nonstick cookware, pyrex and various plastics totally altered the culinary landscape from the 1950s until the 2000s, when cast iron saw a sudden resurgence. Viewed as rustic and reliable in a time when seemingly everything was built to break, cast iron brought a taste of the past into the present while also enhancing the flavor and the sear on everything it touched.

So how is cast iron cookware produced today?

It all starts with pig iron and steel scrap in a factory. Iron is very easy to recycle in a factory setting, so a mixture of scrap and defective cookware can be used to supplement the process ensuring very little waste outside of the energy required to produce the items to begin with. Pig iron is loaded into a furnace along with scrap collected by a giant magnet on a crane. It is smelted at a temperature of at least 2.500 degrees Fahrenheit and slag is skimmed off the top by a large robot arm.

Sand molds are utilized to create the desired shape of a pan. This sand doesn’t become glass until it is subjected to temperatures of at least 3,100 degrees F, allowing it to be reused several times. The sand is fed into a two-part die that presses the sand together and compacts it into the desired shape. This is very similar to using a molded bucket at the beach to create a sand castle. Pressure packs the sand together so that the mold doesn’t lose its shape. Molten iron is squirted into the mold, which can then be knocked off the new pan once it has been adequately cooled. The sand from the mold is cycled back into the production process to be reused in new molds. This sand is a lot like the sand you’ll find at City Beach, but it has been turned black by heat and carbon.

Molded pans are then hung on moving racks and sprayed with a soybean oil and heated to season them. This oil creates a protective barrier over the iron, and is crucial to maintaining the longevity of the cookware. A fun extra tidbit is that excess oil forms a droplet at the bottom of the pan as it hangs, and a worker is assigned to burn it off with a high-powered torch.

Depending on the process, there’s anywhere from a 5% to 10% rate of defective pans, which is an acceptable margin in this field. These pans are sorted out before reaching distribution and are recycled back into the scrap heap to begin the process all over again. Pans that pass inspection are packed into cardboard boxes and stacked onto pallets that are then loaded into a distribution center before being shipped off to their final destination, be it your home or local store.

It’s a fascinating and entertaining process to watch, which I would highly recommend you do from the computers at your local library; after you’ve done that, you’re just a few steps away from checking out a cookbook to test out your grandmother’s old cast iron pan.

Stay curious, 7B.