Science

The Science of Ice in Cocktails

Bartenders weigh in on shape, size, cut, and clarity—and how to choose the right ice

Ice in a cocktail
Photo illustration by Jeff Quinn.

The greatest misconception about ice in cocktails, says Francis Schott, the cofounder of Stage Left restaurant in New Brunswick, New Jersey, “is that it cools drinks just by being cold. It doesn’t—it cools drinks by melting.”

When a bartender chills a drink, heat leaves the liquid, and it has to go somewhere. Raising the temperature of a gram of ice by 1 degree C will draw about 2 joules of energy from the surrounding cocktail. But melting a gram of ice pulls 333.5 joules—two orders of magnitude more cooling power. Melting ice is an extremely efficient way to cool a drink, so much so that in his cocktail treatise Liquid Intelligence, Dave Arnold dubs it the Fundamental Law of Traditional Cocktails: “There is no chilling without dilution, and there is no dilution without chilling.” That property of ice is one of the tenets underlying the contemporary focus on high-quality bar ice.

The Modern History of Cocktail Ice

Schott gives a little backstory on cocktail ice: “Until the ’80s,” he says, “there was a Kold-Draft machine in every bar, making solid 1-inch cubes. It was the best ice in the world, made by the worst machine in the world, notorious for breaking down all the time.” The Japanese equipment manufacturer Hoshizaki saw that unreliability as an opportunity and brought highly efficient ice machines to the U.S. “Those machines just didn’t break,” Schott says. “And they could make ice in half or a third of the time.”

Why were the Hoshizaki machines so efficient? The ice they made was in pieces that were smaller and had more surface area, says Schott, “either hollow cubes or little half-moons.” The greater ratio of surface area to volume meant the ice was quicker to make but also quicker to melt. And that makes a very significant difference to a drink.

“By the time we opened in 1992,” says Schott, “everybody had switched to Hoshizaki.” But Stage Left, working with cocktail pioneer Dale DeGroff, decided to buck the trend and return to cubical ice. “You cannot make really great cocktails with that half-moon ice,” says Schott. “The Kold-Draft people said we were the first new machine they’d sold in New Jersey in a decade. When our Kold-Draft machine would crap out, we’d use half-moons, and every cocktail we made would taste completely different, because everything was watered down about 20 percent more.”

“Today,” Schott says, “the first move of anybody getting into the modern cocktail movement is to go back to Kold-Draft-style ice.” Hoshizaki now makes machines that produce large “gourmet” cube-shaped cubes.

The Effects of Air

As a cocktail is flung back and forth over the ice in a shaker, it gets cold fast, but the agitation has another important effect: It incorporates a lot of air into the liquid. And the quality of the ice makes a difference in that respect as well.

Though he’s not positive why, Arnold has observed that the presence of a large ice cube in the shaker—the 2-inch kind—yields a cocktail with much better froth than the same drink shaken over small ice. His New York City-based food science development company, Booker and Dax, even manufactures a reusable plastic Cocktail Cube that gives the texture of a large-cube shake without incurring the expense of an actual large ice cube in every shaken drink.

Because of its shape, small half-moon-style ice also fills more of the space in a glass than cubes do. “With the half-moon ice,” says Schott, “a 2-ounce pour of Scotch will fill three-quarters to the top of the glass. With [1-inch] Kold-Draft ice, it’s the same 2 ounces of Scotch, but the customer [looks at it and] says, ‘Is this all you got?’”

Getting Clarity

As water crystallizes into ice, any minerals and gases dissolved or suspended in the liquid are pushed out of the way, leaving behind almost pure H2O. Whether the water was distilled or drawn from a tap or a special Argentine aquifer, the resulting ice is the same.

At least, that’s how it’s supposed to work. But when a standard freezer or half-moon machine makes ice cubes, the freezing happens rapidly and from all directions at once. The outside of the cube freezes first, and when the interior solidifies, those gases have nowhere to escape to. They get stuck in the ice, giving it a cloudy appearance and frangible texture.

“We want all our ice to be beautiful,” says bartender Chris McLeod of Dutch Kills bar in Queens, New York. And beautiful ice is ice that’s as clear as water. Dutch Kills uses a Clinebell ice machine, which freezes a tank of water slowly, from one direction, keeping the surface gently agitated to make sure not a single air bubble is trapped in the 300-pound blocks of ice the machine ultimately produces. After lifting a block from the machine, a full-time ice specialist in the back room at Dutch Kills uses “chainsaws and bandsaws” to render it into usable sizes: 2-by-2-by-3-inch blocks for Old Fashioneds and the like, 1-inch cubes for shaken drinks, and a “spear,” shaped like a stick of butter, that fits neatly in a highball glass.

“The reason the cocktail took off in the U.S. in the late 1800s is that the U.S. was the first country to figure out how to harvest, store, and distribute large blocks of ice from ponds and lakes,” says McLeod. “The idea is that the experience at Dutch Kills will be more like what people used to drink back then.”

The majority of bars that use clear ice buy it rather than making it. The machines take up a lot of space and require not only custom plumbing but also the machinery and trained personnel to hoist the 300-pound blocks and cut them to size. Dutch Kills’s offshoot business, Hundredweight Ice, provides cut ice to about 75 clients throughout New York City, in “packs” of 50 cubes (a pack of 2-inch cubes, for example, sells for about $60). “Some bars,” McLeod says, “get two or three packs a week; some get 50-plus.”

At the Manhattan bar Existing Conditions, which is run by Arnold and Don Lee in collaboration with Greg Boehm and, as of this writing, is just about to open, a Hoshizaki machine makes 2-inch cubes—but, says Lee, they’re “just for shaking with. When we put ice in front of a customer, it has to be perfect ice.” For a drink served over an ice cube, the bar uses a cube hand-cut from a 13-inch-square block made in a machine affectionately called the mini-Clinebell. Created by Vancouver ice specialist Cameron Bogue, it uses the same unidirectional freezing method as the Clinebell but on a smaller scale—and produces a more wieldy set of four 50-pound blocks at a time.

Not all high-end ice is clear ice, though. Aviary, a cocktail bar with a branch in Chicago and one in New York City, makes ice cubes out of flavored “stocks” in molds in a blast freezer. As the ice melts in a drink, the flavor profile shifts. “Our drink prices are pretty high, but the ice adds value,” says Aviary’s beverage director, Micah Melton. (Cocktail prices start at around $18) “Instead of having one drink, you have how it tastes right away, how it tastes after one minute, after two minutes … You get 10 or 12 different drinks in one glass.” He explains how bright red ice cubes made from Fresno pepper juice gradually turn a standard margarita on the rocks into a spicy margarita, and how milk ice in an espresso cocktail lets it evolve into “essentially a White Russian.”

Special Shapes

“If you can cut a block of ice into a diamond shape, that’s great,” says Schott, “but it’s just aesthetic. Aesthetics are a big part of drinks, but in terms of melting and cooling, the difference between a ball or a diamond or a cube isn’t anything.” The number that matters is the ratio of surface area to volume—the lower the better—and for a 2-inch cube and a 2-inch sphere, the ratios are the same. A half-moon shape has much more surface area relative to its volume. “You need the right size,” says Schott, “and that’s it.”

When a drink calls for rapid chilling and high dilution—like a mint julep or Moscow Mule—most bars use crushed ice, but Aviary makes BB-sized spheres of ice in custom-designed trays. “We weigh it out—1,200 pieces of that ice go into one drink,” Melton says. “If you use crushed ice, you have some small pieces, some large pieces. This is more effort, but [with the spheres] it’s more consistent, so if we make two of the same drink, they’re exactly the same.”

For decades, ice in drinks went more or less unnoticed, but a more nuanced understanding of it has provided a key to enhancing the quality of today’s cocktails.

Paul Adams is the senior science research editor at Cook’s Illustrated. He lives in New York City, where he writes about food and drinks.

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