When we bake a food, we surround it with a hot enclosure, the oven, and rely on a combination of radiation from the walls and hot-air convection to heat the food. Baking easily dehydrates the surface of foods, and so will brown them well provided the oven temperature is high enough. Typical baking temperatures are well above the boiling point, from 300 to 500°F/150–250°C), and yet baking is nowhere near as efficient a means of heat transfer as is boiling. A potato can be boiled in less time than it takes to be baked at a much hotter temperature. This is so because neither radiation nor air convection at 500°F transfers heat very rapidly to food. Oven air is less than a thousandth as dense as water, so the collisions between hot molecules and food are much less frequent in the oven than in the pot (this is why we can reach into a hot oven without immediately burning our hand). Convection ovens increase the rate of heat transfer by using fans to force more air movement, and significantly reduce baking times.