The Expanding Iron Pan: Understanding Thermal Expansion

Cast iron pans are a popular kitchen item, known for their durability and versatility. Constructed from a sturdy alloy of steel and carbon, these pans can stand the test of time and be used for various cooking methods, from searing steaks to baking cornbread. One unique characteristic of cast iron is its ability to store and distribute heat evenly. This is because cast iron is a dense and heavy material with high volumetric heat capacity and emissivity, allowing it to retain and expel heat effectively.

However, cast iron does have some drawbacks. For instance, it takes longer to heat up compared to other materials like aluminium due to its poor thermal conductivity. Additionally, cast iron may not be suitable for cooking delicate foods as it gets extremely hot and retains heat for extended periods. Despite these minor limitations, cast iron pans remain a favourite among home cooks and professionals alike.

Does an iron pan expand?

It is unclear whether an iron pan expands or not. However, cast iron pans are known for their ability to store and retain heat. This is due to their high volumetric heat capacity and high emissivity, which allow them to stay hot even after being removed from the heat source. Cast iron pans are also touted for their durability and ability to withstand nicks, dents, and scratches.

Cast iron pans are constructed from an alloy of steel and carbon, which gives them their characteristic properties. They are often seasoned with a layer of polymerized oil, which helps to create a non-stick surface and protect the pan from rusting.

When it comes to cooking, cast iron pans are versatile and can be used for searing, frying, baking, and even deep-frying. They heat up relatively slowly compared to other materials like aluminum, but once hot, they provide a consistent and even heat source. This makes them ideal for dishes that require a constant temperature and even heat distribution, such as deep-frying and searing steaks.

In addition to their heat retention properties, cast iron pans can also add significant amounts of iron to your food. This is especially true for acidic and moisture-rich foods like applesauce and spaghetti sauce. However, it is important to note that cooking certain foods in cast iron, such as corn tortillas and liver with onions, may not result in the same increase in iron content due to shorter cooking times and less contact with the pan.

How does an iron pan store heat?

An iron pan's ability to store heat is due to its high volumetric heat capacity. This means that once it's hot, it stays hot. This is especially useful when searing meat, as the pan can maintain a high temperature even after the cold meat is added.

The high heat retention of cast iron pans is due in part to their high thermal mass. They are dense, heavy pans that can distribute heat evenly and retain it for an extended period. This makes cast iron ideal for dishes requiring long cooking times and even heat distribution, such as cornbread or slow-cooked meals.

Cast iron pans are also amorphous solids, meaning their atoms don't line up in a crystalline structure. This makes them relatively poor conductors of heat, so they take longer to heat up and cool down. This can be advantageous when cooking as it gives you more control over the temperature, but it also means that cast iron pans need to be preheated slowly over low heat or moved around on the burner to ensure even heating.

The high emissivity of cast iron pans is another factor in their heat retention. Emissivity is the tendency of a material to expel heat energy from its surface in the form of radiation. Cast iron has a high emissivity rating, so when cooking in a cast iron pan, you're not just cooking the surface in contact with the metal, but you're also cooking a good deal of food above it. This makes cast iron ideal for dishes like hash or pan-roasted chicken and vegetables.

What foods are best cooked in an iron pan?

Cast-iron skillets are incredibly versatile and can be used to cook a wide variety of foods. Here are some of the best foods to cook in your cast-iron pan:

Meats

Cast iron is excellent for cooking meats, especially when you want a nice sear on the surface. The high heat retention of cast iron makes it perfect for searing steaks, giving them a beautiful crust. You can also use it for whole roasted chicken, chicken fried steak, and bacon. Just remember to start cooking bacon in a cold pan to prevent it from becoming tough.

Pizza

Cast iron pans are ideal for making pizza, as they can create a thick and crispy crust that is golden on the bottom but puffy and soft underneath. The high heat of cast iron helps create an open, airy, and chewy crumb structure in the pizza dough.

Eggs

While it may take some practice to master, cooking fried eggs in a cast-iron skillet is a great way to develop a good seasoning on the pan. The key is to ensure that your pan has a well-seasoned surface before attempting this delicate task.

Breads

Cast iron is perfect for baking bread, cornbread, and even tortillas. The even heat distribution and heat retention of cast iron result in bread with a crispy, golden crust and a fluffy interior.

Vegetables

Cast iron is excellent for roasting or charring vegetables. Brussels sprouts, for example, can be tossed in a cast-iron skillet and roasted in the oven, resulting in a dish that even those who don't typically enjoy Brussels sprouts will eat.

Desserts

Cast iron skillets are great for baking desserts like cobbler, apple pie, and even cookie cake. The even heating of the skillet ensures a consistent crust on your desserts.

One-Pot Meals

Cast-iron skillets are also perfect for one-pot meals, such as lasagna, macaroni and cheese, and oatmeal. The heat retention of cast iron ensures that your meal stays warm throughout the cooking process.

How do you season an iron pan?

Seasoning an iron pan is a crucial step in maintaining your cookware and ensuring that your food doesn't stick to the pan. Here is a step-by-step guide on how to season an iron pan:

Step 1: Wash and Dry Your Pan

Start by giving your pan a good scrub with warm, soapy water. This is especially important if your pan is new, as you don't know what it has been exposed to during manufacturing and shipping. Make sure to dry the pan thoroughly after washing. You can use a towel to wipe it down, and then place the pan on a stovetop flame for a minute or two to drive off any remaining moisture.

Step 2: Apply Oil to the Pan

Once your pan is clean and dry, it's time to rub it all over with cooking oil. Vegetable, canola, grapeseed, and corn oil are all good choices. Use a paper towel or lint-free cloth to apply a thin, even layer of oil to the entire pan, including the handle, inside and out. Make sure to buff the pan well after oiling to remove any excess oil. This step is important because excess oil can pool during the seasoning process, forming hardened droplets or turning sticky if left unused.

Step 3: Heat the Pan in the Oven

Place the oiled pan in a preheated oven. The ideal temperature is between 450°F and 500°F (230°C to 260°C). It's recommended to put the pan upside down on an oven rack with a baking sheet or aluminium foil on the rack below to catch any oil drips. Leave the pan in the oven for about an hour. It may get smoky, so make sure your kitchen is well-ventilated. During this time, the oil will undergo a process called polymerization, where it bonds to the metal and forms a hard, plastic-like coating.

Step 4: Repeat the Process

After an hour, remove the pan from the oven and let it cool. You may want to rub the pan with another light coat of oil and buff it again. Then, repeat the process of oiling and heating the pan in the oven for another 30 minutes to an hour. You can do this three to four times to build up a good initial layer of seasoning. Once you're done, simply let the pan cool, and it's ready for cooking!

Maintenance:

After the initial seasoning, maintenance is much simpler. Each time you cook with oil in your cast iron pan, you will be adding to the seasoning. Simply using your pan regularly will help maintain its non-stick properties and protect it from rust. If you notice that food is starting to stick or the pan looks dry, you can repeat the seasoning process described above.

How do you clean an iron pan?

Cast iron pans are a versatile and durable option for any kitchen. They can be used for anything from searing steaks to baking cornbread. But how do you clean them?

Firstly, it is important to note that cast iron pans should always be washed by hand. They should not be put in the dishwasher as this will remove the seasoning and likely cause rust. You can use a small amount of soap to clean cast iron, contrary to popular belief. However, large amounts of soap can strip the seasoning off the pan, so it is important to re-season the pan if this happens.

To clean your cast iron pan, start by washing it by hand with hot water and a sponge or stiff brush. Avoid using steel wool, as this can damage the pan. For stuck-on food, use a pan scraper or a nylon scrubbing brush. If the food is particularly stubborn, you can simmer a little water for 3-5 minutes and then use the scraper after the pan has cooled.

Once the pan is clean, dry it promptly and thoroughly with a lint-free cloth or paper towel. If you notice any black residue on the towel, don't worry, it's just seasoning.

The final step is to rub a very light layer of cooking oil or seasoning spray onto the surface of the pan. Use a paper towel to wipe the surface until no oil residue remains.

And that's it! Your cast iron pan is now clean and ready to be stored away in a dry place.

Frequently asked questions