Editor's note: For more fun with woks, check out Thy Tran's compendium of wok shopping tips, history, and the meaning of BTUs here.
When you think of a wok, chances are you picture the curve of the wok, with its rounded bottom and sloping sides. What distinguishes it in design also distinguishes it in function. Both the concave shape and material of the wok allow heat to distribute evenly and prevent the formation of “hot spots,” which cause food to stick and burn.
The most common materials for woks are carbon steel and cast iron. While cast-iron skillets are poorer heat conductors than aluminum or copper skillets, they have the advantage of being able to hold more heat and distribute it more uniformly. Cast-iron skillets also accumulate a natural nonstick coating from the fats and oils of cooking. This “seasoning” is the result of oils breaking down and reacting to form a carbon-containing residue. Carbon is an element that takes many forms (ranging from coal to diamonds), but in this case, the carbonized layer protects the metal from corrosion and reduces sticking that would otherwise result from food hitting a bare, hot metal surface.
When nestled in the flames of a fire, the sloping sides distribute heat evenly among the food being cooked. The technique of pushing food away from the center and up the sloping edges regulates heat distribution and allows cooking to alternate between higher and lower temperatures, which ultimately gives the chef more control.
Jamie Bresson is a chemical engineer at Calera Corporation. Fumei Lam is a postdoctoral researcher in mathematics at the University of California.