A flame diffuser or heat diffuser is a piece of equipment used on gas stoves, as well as electric stoves, to evenly distribute the heat of a burner or heating element. The advantage of using a heat diffuser is that it prevents hot spots from forming and potentially ruining food.
Heat or flame diffusers are sold under a variety of brand names. As of 2015, companies such as Broadway Panhandler, The Brooklyn Kitchen and Flamer Tamer offer models that sell from $4 to $25. They are typically circular in shape, with either perforations or slits cut in. Heat diffusers range from 6.5 to 12 inches in diameter. Different sizes better accommodate the wide variety of burner and heating element sizes available on the market. They are usually made from tin-plated steel, aluminum or cast iron and often feature a handle, sometimes encased in a cool-grip material like wood.
Heat diffusers are especially useful for low-heat applications like melting chocolate, braising or cooking a delicate sauce. Overheating such dishes is easy to do on a traditional burner and tends to scorch the food item. They also prevent pan discoloration that can occur with prolonged high heat, as well as balancing heat for small cookware items such as espresso makers or butter warmers.