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How one man’s quest to mix the perfect drink led him to his freezer—and how you can recreate what he discovered at home


The key to a truly stellar cocktail may go beyond top-shelf liquors and trendy mixing techniques. In fact, the secret ingredient may be something that is odorless, colorless and tasteless, and easily made at home—ice. Not just any ice, says Mark Davidson, a software-engineer-by-day, cocktail-enthusiast-by-night. “The secret sauce is pure ice. It makes a clear, clean cocktail.”

If you thought the ice in your freezer was already pure, take a closer look. Little cracks and bubbles on the inside of the cube are evidence of trapped impurities like chlorine, organic compounds and suspended particles which result in opaque, muddy streaks. Not only are they visually unappealing, but these traditional ice cubes melt quickly, diluting a high-quality cocktail with low-quality water.

Driven by a desire to create a perfect gin and tonic, Davidson, a former scientist, had already delved deep into the world of home cocktail- making when a book, Liquid Intelligence: The Art and Science of the Perfect Cocktail, pushed him further down the rabbit hole with a recipe for ice.

The process removes the impurities and gases that are found in water and freezes it by methods that render the result perfectly clear. The ultimate presentation is dramatic, especially when using premium tonic and gin, Davidson says. “If I get it right, it looks like a clear glass of water with a lime, and you can’t see the ice cube.”

To create pure ice at his home in Scotts Valley, Davidson boils a gallon or two of tap water twice to remove chlorine and other basic impurities before pouring the water into an insulated cooler. After the water cools to room temperature, he freezes the water in the cooler, lid open, for 36 to 48 hours.

In a traditional ice cube tray, which is not insulated in any way, cold air hits the water from all sides, which pushes impurities towards the center of the cube. As the ice freezes and expands, mini-explosions shatter the center of the cube, creating the telltale white center. The pure ice method uses directional freezing, with cold air cooling the water from one direction. As the water freezes from the top down, its natural crystalline structure builds piece by piece while pushing impurities to the bottom of the cooler. Davidson, who grew up in Toronto, explains that this is similar to how lake water freezes.

Once frozen, Davidson lets the outside of the ice come to room temperature for about 30 minutes (the surface almost sweaty and no longer frosty) before sliding the block out of the cooler. With the exception of a couple inches of frosty-looking impure ice at the bottom, the ice is beautifully clear.

The last step—cutting the block into cubes that will fit in your glass—is arguably the hardest. After tempering the block, Davidson scores it with a knife and, using a cleaver and a plastic mallet, shears away slices and divides them into 2-inch cubes—with varying success. “Strange shapes are good enough. The effect, aesthetically, is still amazing,” he says. The important thing is to avoid small cubes and try instead for large blocks, which melt much more slowly. “They can last 30 to 40 minutes without excessive dilution and the flavor profile doesn’t change dramatically.”

The cubes can be kept in the freezer on a tray covered with a lid. But before using them in a cocktail, Davidson advises taking them out of the freezer and letting them sit in a bowl for 20 to 30 minutes; if their surface has not first reached room temperature, the cubes may crack when you pour other ingredients over them.

Davidson acknowledges with a laugh that the process may seem lengthy. “But all you really need is space, a little patience and materials at hand,” he says, “and the results are worth it.”

Lily Stoicheff is an eater and writer living in Santa Cruz with a soft spot for points of historical interest and a passion for pickles that threatens to take over her fridge.


Mark Davidson’s Perfect Gin and Tonic

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Lily Stoicheff is an eater and writer living in Santa Cruz with a soft spot for points of historical interest and a pickling passion that threatens to take over her fridge.