Grilling and Broiling: Infrared Radiation

Grilling and broiling are the modern, controlled versions of the oldest culinary technique, roasting over an open fire or glowing coals. In grilling, the heat source is below the food; in broiling, above. Though air convection contributes some heat, especially as the distance between heat source and food is increased, broiling is largely a matter of infrared radiation. The heat sources used in these techniques all emit visible light and so are also intense radiators of infrared energy. Glowing coals or the nickel-chrome alloys used in electrical appliances reach about 2,000°F/1,100°C, and a gas flame is closer to 3,000°F/1,600°C. The walls of an oven, by contrast, rarely exceed 500°F/ 250°C. The total amount of energy radiated by a hot object is proportional to the fourth power of the absolute temperature, so that a coal or metal rod at 2,000°F is radiating more than 40 times as much energy as the equivalent area of oven wall at 500°F.