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Salt to reduce boiling time

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I know salting water causes it to have a lower boiling temperature, so it reaches the boiling point sooner. My question is whether there's a difference in the time it takes to reach the boiling point if you add the salt at the beginning (when the heat is first applied) or later (after the heat has been applied a while, and the water's temperature is already a little higher).

I ask this out of "scientific" curiosity. I can't imagine the time difference would be that big, if there were one.

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  1. Really? I always thought that adding salt to water increased its boiling temp., so that it takes slightly longer to reach boiling . . . my Italian friends always say to salt the pasta water once it's boiling so that you don't slow down the process at all . . . .

    GG
    http://www.semisweetonline.com

    3 Replies
    1. re: gansu girl

      GG is correct -- salt water boils at a higher temperature. Here's a great piece that discusses and dispels kitchen water myths: http://itotd.com/articles/521/water-f...

      I think the real reason to add salt after the water is already boiling is that it dissolves faster and you don't risk pitting your pot with undissolved salt crystals sitting on the bottom (although most modern cooking vessels won't pit anyway).

      1. re: gansu girl

        Yikes. I guess I fail both basic chemistry and cooking. I always thought the mixture would have increased entropy, and therefore boil at a lower temperature. What did I forget from high school chemistry ?

        OK, I just googled this. (Should've done that in the first place.) The increased entropy results in a lower freezing point, but a higher boiling point.

        Some articles also mentioned not waiting until the water was boiling to throw in the salt, because it might induce an immediate boilover.

        1. re: dump123456789

          The boilover effect is actually a fact. It ocurs after adding the salt by making the water boil more vigorously for a few seconds or even "explode." I've never actually had water boil over when adding salt, probably due to the quantity of water I was boiling and the amount of salt I added to same.

          Then there's this:

          "Adding salt to water raises the boiling point. This is a scientifically measureable effect, but it takes 2 oz. of salt to raise the boiling point of 1 liter nearly 2 degrees F, so the effect is not noticeable in your average kitchen. Salt added to water also lowers the freezing point. "