Stirring vs. shaking a cocktail

Stirring and shaking obviously result in the various ingredients being mixed together, but both actions also cool and dilute the cocktail being mixed. The key difference between the two mixing methods is that the violent action of shaking achieves the same results quicker. The same degree of cooling and dilution can be achieved with 15 to 20 seconds of shaking as 90 to 120 seconds of stirring.

With few exceptions, (most notably the Old Fashioned) drinks are not stirred for longer than 30 to 45 seconds, so do not end up as cold or as diluted as if they had been shaken.

Why stir then? Stirring merely chills and dilutes a cocktail whereas shaking additionally changes its texture. The ice, being violently shaken about inside the shaker, also aerates the drink with tiny air bubbles, which are held in suspension in the liquid, giving the cocktail a cloudy appearance. Stirring, on the other hand, has the benefit of delivering a crystal-clear cocktail.

Hence, bartending 'law' has it that drinks made with only clear ingredients should be stirred and drinks with cloudy ingredients such as citrus juice, milk or cream should be shaken. Laws are, of course, made to be broken, and while it is true that any drink which can be stirred can also be shaken - and occasionally might even be better for it (should, for example, a Vodkatini be shaken or stirred?) - drinks containing egg white, cream and, to an extent, milk, should always be shaken.