Shaken vs. Stirred: Why Does It Matter How You Chill a Cocktail? Ask Paul

Beyond thoroughly combining the ingredients, the purpose of shaking or stirring a cocktail is all about causing ice to melt. That accomplishes two essential things: It makes the drink cold, and it adds in a certain amount of water. But each method leads to different final results.

Before we get to how the methods differ, let’s take a close look at what the ice is actually doing in a drink. Ice doesn’t make the drink cold simply by being cold itself; its cooling power is only unleashed when it undergoes a phase change—that is, when it starts to melt. That’s because melting ice draws heat from its surroundings. A lot of heat.

If you put half an ounce of ice-cold water (at 32 degrees Fahrenheit) into 2 ounces of room-temperature liquor (68 degrees Fahrenheit), the mixture will drop to 61 degrees.

But if you put half an ounce of ice (also at 32 degrees Fahrenheit) into that same liquor and allow it to melt, the temperature of the whole drink will come down to 30°F. How is that possible?

It’s all about that phase change. Any time a substance changes phase—from solid to liquid, liquid to gas, or vice versa—there’s energy involved. To melt a single half-ounce ice cube requires a specific amount of heat energy: 4.7 kilojoules. If the cube is in a drink, it pulls that heat from the drink. And pulling 4.7 kilojoules out of 2 ounces of room-temp liquor is enough to chill it to 30 degrees.

The water that melts from the ice dilutes the drink, of course—and while that might not seem like a benefit, cocktail recipes are designed with this in mind. The addition of water helps harmonize the flavors of a cocktail and soften any harshness, turning it from a mere combination of liquors into a pleasing drink. In a typical cocktail, 25 to 35 percent of the volume is made up of water that was added by melting ice. And our palates are sensitive to even slight variations in the ratio of water to alcohol.

If you simply add ice to a liquid and leave it alone, the ice will melt very slowly. As it melts, each cube becomes surrounded by cold liquid meltwater, which slows down the melting process. If we want to cool the drink in a hurry, we need to move the ice around, either by stirring or by shaking.

Stirring the ice around in the drink hastens melting (and hence chilling). In our testing, 30 seconds of stirring will bring a martini down to a pleasant 28 degrees; but it keeps getting colder over the course of a couple of minutes of stirring, and 90 seconds of stirring gets it to a lovely 24 degrees. Dilution and chilling go hand in hand, so while the 30-second drink contains about 25 percent added water, the colder drink contains 32 percent. (In tastings, a majority preferred the more dilute martini.)

Shaking agitates the ice and liquid together quite a bit faster, so that you can achieve a temperature of 20 degrees Fahrenheit in about 20 seconds.  

Stirred drinks retain a beautiful clarity due to the gentle treatment. This is the method usually chosen for drinks such as martinis, Manhattans, and negronis, which are supposed to be served clear and cool. The temperature of a stirred drink, a few degrees warmer than a shaken one, allows the botanical, bitter complexities of these spirit-forward cocktails to shine forth.

Shaking is a more violent treatment, generally used for drinks that contain citrus or cream (a daiquiri, a Creema di Leema) and hence will never have the clarity of a stirred drink. A shake, while rapidly chilling the drink to a brisk and refreshing temperature, also incorporates plenty of tiny air bubbles, giving the drink a frothy texture, and ingredients like juice and dairy maintain the froth that would otherwise dissipate quickly. Vigorous shaking can leave you with shards of ice floating on the drink as well, which some people enjoy and others hate. 

Ask Paul Adams, senior science research editor, about culinary ambiguities, terms of art, and useful distinctions: paul@americastestkitchen.com