by Conor Friedersdorf
Forget about what James Bond would do -- here's what you need to know:
Cocktail shaking is a violent activity. If you shake for around 12-15 seconds (though shaking longer won’t hurt), and if you aren’t too lethargic, neither the type of ice you use nor your shaking style will appreciably affect the temperature or dilution of your drink. Shaking completely chills, dilutes and aerates a drink in around 15 seconds, after which the drink stops changing radically and reaches relative equilibrium. Shaking is basically insensitive to bartender-induced variables. See my post on the Science of Shaking.
Stirring is different. Think of stirring as inefficient shaking. It can take over 2 minutes of constant stirring to do what shaking can accomplish in 15 seconds. No one stirs a drink for 2 minutes, so the drink never reaches an equilibrium point. All the bartender-induced variables size of ice, speed of stirring, duration of stirring, etc. make a difference in stirred cocktails, so bartender skill is very important in a stirred cocktail.
Because stirring doesn’t reach equilibrium, stirred drinks are warmer and less diluted than shaken cocktails. Stirred drinks, unlike shaken ones, are not aerated. Stirring does not alter the texture of a drink it merely chills and dilutes. A properly diluted cocktail stored at -5 degrees Celsius in a freezer is indistinguishable from a properly stirred one.
Don’t believe me? The proof’s in the long story.