WOK: Carbon Steel vs. Cast Iron

Carbon steel is refined iron, cast iron is pig iron. As for woks, carbon steel woks are noticeably superior to cast iron woks.

Cast iron is a primary product of iron smelting, with a high carbon content and a relatively brittle texture. It can only be cast into shape using molds, hence the name "cast iron wok pan".

The Difference Between Carbon Steel and Cast Iron

Carbon steel is the product after removing carbon from cast iron. It has good ductility and can be forged into shape. From the perspective of cookware, the main difference between metals lies in their thermal conductivity and specific heat capacity. The distinction between the two can be seen in the diagram below.

The thermal conductivity of impacts cookware in two main ways:

1. The higher the thermal conductivity, the faster the cookware heats up.

2. The higher the thermal conductivity, the more uniform the temperature distribution across the cookware, resulting in better heat distribution.

As shown in the table above, cast iron has only half the thermal conductivity of carbon steel. It means carbon steel wok significantly outperforms cast iron wok in terms of heating speed.

In Chinese-style cooking, sufficient heat is often required to ensure the desired texture and color of the dishes. Due to its lower thermal conductivity, cast iron wok is inferior to carbon steel wok in terms of its physical properties.

As mentioned earlier, cast iron, with its high carbon content, cannot be forged and shaped but must be cast. This contributes to the considerable weight of cast iron wok, which is typically more than twice the weight of carbon steel wok of the same size.

However, the thickness resulting from casting also improves the heat distribution and retention of cast iron wok. This makes cast iron woks more suitable for stewing or frying. Enamel-coated cast iron pots, which have become popular in recent years, are essentially porcelain-coated cast iron pots. Meanwhile, cast iron skillets are commonly used in Western cuisine for searing steaks.

Conclusion: carbon steel woks are more suitable for stir-frying due to their excellent heat conduction, which allows for more sensitive temperature control. Cast iron woks are better suited for use as stewing or frying pans.

Exception: When the household's heat source is very weak, cast iron woks may be more suitable because adding ingredients to the wok lowers the temperature, and cast iron retains heat better, resulting in less fluctuation in temperature. For households using gas stoves with a heat output greater than 4kw, wrought iron woks are recommended, while for those with less than 4kw, cast iron woks are preferred. Induction cooktops also favor cast iron woks or tri-ply stainless steel woks.

The Color of the Wok

Regarding the color of woks, whether it's cast iron or carbon steel, under normal circumstances, both exhibit a silver-white fracture surface. Even the commonly seen hand-forged wrought iron woks also have a silver-white appearance.

As we all know, iron is a relatively reactive metal that oxidizes to form iron(III) oxide, also known as rust, especially in the presence of water. This is why sometimes leaving water residue in a wok can lead to rusting overnight.

To address this issue, iron woks are often treated with nitrided to prevent rusting. Nitrided involves the strong bonding of nitrogen with the surface of the iron wok, forming nitrided compounds. Nitrogen occupies the oxygen sites, thereby preventing rusting. Consequently, nitrided iron woks typically have a gray-black color.

The image below shows the unboxing of a nitrided iron wok I recently acquired, displaying an overall distinct gray-black coloration.

In addition to nitrided, another common method to prevent rusting is through oil seasoning, a technique employed by Lodge cast iron woks. Essentially, this process involves applying oil to create a protective barrier against oxidation. Edible oils are typically used, but it's still advisable to thoroughly clean the pan upon purchase.

There are a few points to consider when selecting a wrought iron wok. You'll need to decide whether to opt for a conventional forged wrought iron wok or one with mechanical spinning and nitrided processes. This decision often hinges on budget constraints.

The "Blog" section on our homepage offers a wealth of kitchenware guides. Feel free to explore them for more insights and tips.