About Boiling Water

• Non-cooks are often described as people who "can't even boil water." Admittedly boiling water is not difficult, but it's worth understanding the process. When water reaches a temperature of 212 F, it converts into steam. Since steam is lighter than water, it rises to the surface in the form of bubbles, and disperses into the atmosphere. Salt and sugar can raise the boiling temperature of water, while altitude lowers it.

Simmer, Gentle Boil, Rolling Boil

• Water passes through several stages of near-boiling as its temperature rises. At temperatures of 140 to 190 F, the surface of the water appears to move gently on its own, stirred by the natural rise of heated water from the bottom of the pot. This is called simmering. Beginning around 190 F and continuing up to the boiling point of 212 F, bubbles begin to appear. When there a steady stream of bubbles disturbs the surface of the water, this is referred to as a gentle boil. When the surface consists entirely of jostling, rolling bubbles, that is a rolling boil.

Cooking at a Full Boil

• Despite the notable difference in appearance, the temperature of water at a full rolling boil is only marginally higher than water at a gentle boil. The difference between the two methods lies in the greater physical motion of the rolling water. Water at a full boil will vigorously agitate any foods that are cooked in it. This is great for pasta, for example, where the constant stirring motion of the water washes away the sticky surface starches, leaving the noodles tender and ready for their sauce. It's less appropriate for eggs, which crack, or potatoes, which turn to mush when boiled vigorously.

Cooking at a Gentle Boil

• Most foods are best cooked at a gentle boil, rather than a full rolling boil. Vegetables hold their shape more reliably when cooked in a gentler fashion, and retain their nutrients better without the jostling effect of a full boil to abrade their surfaces. Grains hold their shape and texture better at a slower boil, and even porridge is less likely to stick and scorch to the pan. Meats should be poached or simmered at even lower temperatures, so their protein molecules will not tighten and toughen from the heat.