What Einstein Kept Under His Hat: Secrets of Science in the Kitchen by Robert L. Wolke Read Free Book Online Page B

coexist, they must get down to this lower temperature by melting some of the ice, a process that absorbs heat and makes the mixture colder. It’s the same phenomenon that makes an ice-and-salt mixture so cold that it can freeze cream in an old-fashioned ice cream freezer. The salt in this case lowers the freezing point, as the alcohol does in the julep.
    The cooling of the goblet’s contents by the bourbon’s alcohol can be so great that on a humid day the moisture in the air will not only condense on the outside of the goblet but actually freeze there, forming a coating of frost. A Tom Collins won’t get cold enough to freeze the moisture on the outside of its glass because it may contain only a few ice cubes and not enough alcohol to lower the freezing temperature very much. In a julep goblet, however, all that crushed ice has a huge surface area at which the ice/water equilibrium can play out its temperature-lowering game on a grand scale.
    For the most spectacular presentation, mint juleps should be made and served in sterling silver—not silver-plated—goblets or cups, rather than in glasses. Glass is a very poor conductor of heat (and cold), whereas sterling silver is 92.5 percent silver, and silver is the best heat conductor of all metals.
    A mere Yankee, I dare not venture to present here a recipe for a mint julep, inasmuch as part of the reason the South is warmer than the North is that Southerners are engaged in perpetual heated arguments about the best way to make one. Find a Kentucky colonel (no, not that one; he’s no longer with us) and ask him.

                                 
SHAKE ’N’ STIR
                                 
    I’ve been having a discussion with some friends about chilling drinks by stirring or shaking with ice cubes—how much ice to use and what the dilution factor would be. One guy said that he uses lots of ice to chill faster and get less dilution. I countered that it may chill faster, but the dilution factor would be the same: less water from each cube, perhaps, but the total amount of melted ice would be the same. Any help greatly appreciated.
    ....
    I ’m with the other guy.
    First, the colder the ice the better. Colder ice will cool the liquid faster, just as colder rocks would do. And melting is not necessary for cooling; cold rocks would do the job as well.
    If two substances are in contact, heat will flow automatically from the warmer one into the cooler one. In this case, heat flows out of the liquid and into the ice. Or, if you will, ice sucks heat out of the liquid. The colder the ice starts out, the more calories of heat it can suck out of the liquid before it reaches its melting/freezing point of 32°F (0°C) and even begins to think about melting. So if the ice is cold enough—far enough below 32°F—there need be little, if any, melting and consequent dilution.
    Second, the more ice the better. Lots of ice in the container forces the liquid into crevices between the ice chunks, creating thin layers of liquid that make efficient thermal contact with the ice surfaces and cool faster than would thicker layers of liquid. Another way of putting this is that the more ice chunks there are, the more ice surface is available for heat exchange with the liquid. So again there’s faster cooling and less, if any, melting—if you don’t leave the ice in too long. The best cooling mantra then, is “Lots of ice, short time.”
    That’s ice cubes , incidentally, not cracked ice. Cracked ice has so much surface area, and the heat exchange between it and the liquid is so efficient, that it will start melting and watering down your drink before you can say Jack Daniel’s.
    Unfortunately, most bartenders’ ice isn’t very cold. It has probably been sitting in the bin for hours, warming up to within a few degrees of its melting point, so it doesn’t have much cooling capacity before it begins to melt and