Boiling Temperature

• Although cookbooks often describe the boiling point of water as a constant, that's only true within certain limits. At sea level, its boiling point is 212 degrees Fahrenheit, but factors, such as altitude and the purity of the water, can affect that mark. If the water contains a high percentage of dissolved salt or sugar, its boiling point rises appreciably because those substances interfere with the water's ability to evaporate. It's a well-tested effect, but in the kitchen, it's more applicable to sugar than to salt.

Try to Concentrate

• How much your water temperature increases is closely related to the amount of salt you're using. A heavily saturated salt solution can raise the boiling point of water significantly, but it has limited culinary use. Even brining a piece of meat for curing seldom requires enough salt to significantly affect the boiling point. Saturated sugar solutions are much more common in the kitchen, especially in candy making. The concentration of sugar required for fudge or caramel can raise the boiling point by 80 to 100 degrees F.

Everyday Cooking

• The amount of salt you use in everyday cooking doesn't bring the water anywhere close to the level of saturation needed to raise the boiling point. It takes about 5 teaspoons of salt, or not quite 2 tablespoons, to raise the boiling temperature of a quart of water by just 1 degree F. That's already a substantial amount of salt, more than most cookbooks suggest for cooking potatoes, pasta, vegetables and most other boiled foods. In short, although salt can raise your water's temperature, it has a negligible effect on ordinary food preparation.

A Few Other Benefits

• Just because salt doesn't cook your food faster, it doesn't mean that you shouldn't add salt. On the contrary, salt serves a number of useful purposes. A moderate amount of salt in the cooking water for vegetables, pasta and other starches seasons them gently but thoroughly, so you won't need to add as much at the table. It also ensures that those starches won't zap the flavors from your sauces, which can be noticeably muted as a result. With dried peas and beans, salt in your water can actually slow cooking rather than speeding it. Salt strengthens the beans' skins, helping them withstand long, slow cooking without breaking down.