8 Things You Didn’t Know About…Boiling Water
We all know by now that, whether you’ve got your eyes fixed impatiently on it or not, the water will always boil, just as most of us have known since elementary school that water boils (more or less) at 212˚F.
And long before humans figured out how to measure temperatures, we’ve been boiling our food. Paleontologists don’t agree on when, precisely, but it’s likely the next cooking technique our ancestors discovered after roasting meat over an open flame. (Probably a long time after, though, since boiling required some sort of vessel sturdy enough to heat liquid to a boil and hold it — hardly as simple as, say, tossing a mastodon steak on a fire.)
Whether you’re cooking rice or pasta, blanching some raw summer vegetables, hard-cooking eggs or making tea, you probably boil water several times a week. It’s one of the easiest things we do in the kitchen, hardly worth devoting much time to. Well, maybe a little.
The boiling point of water decreases about 2˚F for every 1,000 feet in elevation above sea level. That means at a mile high (in Denver, say) water boils at 202˚F.
Why? It all has to do with atmospheric pressure. There’s less pressure at higher elevations, which means it takes less energy to heat the water molecules to a point where they come to the surface and turn to vapor.
Whether you want to watch the pot or not is up to you, but the fastest way to boil water on the stove is really the most intuitive: high heat and a lid. Hot water from your tap also boils faster than cold. (This would seem to go without saying, yet there’s a persistent myth out there that cold water boils faster — perhaps only in the kitchen of that exiled Nigerian prince who just needs your social security number to transfer all his money to you.)
Boiling and simmering are not the same thing. Boiling occurs when a liquid has reached its full boiling point — 212˚F for water at sea level. Simmering, on the other hand, means bringing the liquid to a boil then reducing the heat to around 180˚F.
But you likely don’t rig up a thermometer on the side of your pot every time you cook. So in more kitchen-friendly terms, a boil is rapid and seething, a Wagnerian crescendo of bubbles roiling and bursting. Simmering is quieter and gentler, with a few lazy bubbles floating to the surface.
Poaching is even lazier still — maybe just a bubble or two coming to the top. It’s generally reserved for delicate foods such as eggs and fish.
So your recipe calls for “salted boiling water,” but what does that mean — and why? It’s a matter of taste, plain and simple. While dissolving just about anything in water will raise its boiling point, it’s not by much: you’d have to boil the equivalent of sea water to raise the boiling point a measly 1˚F. In other words, adding salt to boiling water doesn’t change the cooking time in any real way.
How much salt, then, is entirely up to you. A good place to start is about ¼ tsp. for every cup of water. Coarse salt, such as kosher salt, works great. Add it to the water once it’s boiling (which makes a fun fizzy sound), stir a bit to dissolve, then add whatever it is you’re cooking.
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