Cast iron
Cast iron is made from pig iron, which is the product of smelting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting.
Wok
Cast iron woks form a more stable carbonized layer of seasoning which makes it less prone to food sticking on the pan. While cast iron woks are superior to carbon steel woks in heat retention and uniform heat distribution, they respond slowly to heat adjustments and are slow to cool once taken off the fire. Because of this, food cooked in a cast iron wok must be promptly removed from the wok as soon as it is done to prevent overcooking. Chinese-style cast iron woks, although relatively light, are fragile and are prone to shattering if dropped or mishandled.