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Sad Science of Soup


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Soup is the title of a chapter in Herve This' book Kitchen Mysteries, which currently I am reading.  This essay asserts that blowing on soup cools it by disturbing the boundary layer of what is technically smoke (not vapor) above the hot liquid.  @nathanm reached essentially the same conclusion in Modernist Cuisine.


As much as I respect the great minds, I call balderdash.  I maintain blowing on soup cools it primarily by the Joule-Thomson effect, in which a gas is cooled by being forced through an orifice, eg. one's lips.  This is easy enough to prove with an experiment:  with mouth open, blow on soup with all one's might.  Keep blowing, because you will be at it quite a while.


Then purse your lips, as one naturally does when cooling soup, and continue blowing.  The soup cools quickly.  The experiment does not need soup, or even a thermometer.  With mouth open blow on your hand.  Your breath feels warm.  Purse your lips and continue blowing.  Your breath feels cool.


Thank me next time you don't scald your tongue.


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Cooking is cool.  And kitchen gear is even cooler.  -- Chad Ward


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