If you enjoy an occasional whisky on the rocks, congratulations! You’ve already made the first of many difficult decisions whisky lovers face. The next question: Which type of ice should you use in your drink of choice? Years ago, most bars served that hollow “cheater ice” designed to melt on contact and fill your glass. Today, large, square ice cubes that melt slowly are de rigueur for both bars and at-home drinking. At the extreme end, whisky stones promise to chill without dilution. We tested each of these methods to evaluate the ways in which they cool and dilute whisky over time, so you can select the right fit for your whisky the next time you’re chillin’.
Laws of Whisky Thermodynamics
Iskender Sahin, professor and associate chair of mechanical engineering at NYU Tandon School of Engineering, explains what’s happening in the glass.
The Smaller the Ice, the Colder the Whisky
The verdict is in—the smaller ice made our whisky freezing cold—actually even colder: 23º F! That’s because the heat transfer, or the cooling process of the whisky, is proportional to the surface area of the ice. The same volume of small cheater ice or crushed ice has much greater surface area than a single cube, therefore enhancing the cooling of the whisky.
Whisky Stones Never Get as Cold as Ice
Those trendy little soapstones can’t match ice’s cooling powers thanks to a thermodynamic material property called heat capacity. Heat capacity, or specific heat, refers to the amount of heat needed to raise the temperature of a substance one degree. Stones have a lower heat capacity than ice, meaning it is way easier to raise the temperature of a stone than a piece of ice.
Large Ice Is Best for Slow Sippers
As ice slowly melts, your whisky benefits from the power of a phase change. It takes a crazy amount of energy to turn ice from solid to liquid, and according to latent heat, temperature change does not occur during a phase change. So as the ice cube in your dram slowly melts, it is not only holding its cold temperature, but also cooling your whisky.
Swirl It, But Don’t Go Stir Crazy
Shaking and stirring is a good way to cool off a cocktail, but don’t get too carried away trying to cool off your whisky. Although the turbulence effect states that stirring or agitating a fluid will increase heat transfer, or cooling, a glass of whisky is just too small to yield any noticeable results, according to Sahin.