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The Word From the Ice King
An excerpt from Camper English's The Ice Book, on the art of making ice for cocktails.
In the world of cocktails, you see and hear a lot of geeky chatter about ice. Yet much of this ice talk is…well, frankly…hot air. So, when you’re finally serious and ready to learn the art of making ice, there is only one person to turn to: Camper English. This week, in the New York Times, Camper was referred to as the “godfather of making clear ice at home,” among other superlatives. Camper, a former physics scholar turned cocktail writer, has spent the last decade-and-a-half perfecting the technique of creating clear ice, the bartender’s holy grail.
On May 23rd, Camper will release his much-awaited tome on the subject, The Ice Book. If you’re someone who cares about cocktails, I highly recommend pre-ordering The Ice Book—which will assuredly be the most talked-about book for cocktail nerds this summer and beyond. Along with his earlier book, Doctors and Distillers: The Remarkable Medicinal History of Beer, Wine, Spirits, and Cocktails, Camper has positioned himself as a leading authority of booze science.
I am thrilled that Camper has given us permission to publish an excerpt of The Ice Book in today’s newsletter, along with a cocktail recipe below. Read on for some serious ice wisdom and knowledge from the master.
Excerpt from The Ice Book, by Camper English
Clear ice. It’s frozen water. Why all the fuss?
You could say the same thing about pizza, bagels, beer, or any other edible or nonedible items—cast-iron pans, chef’s knives, or crystal wine glasses—that we obsess over. We want the very best version of our favorite simple things.
Crystal-clear, high-quality ice is somewhere between food and a tool. Yes, clear ice tastes better (but not much better) than milky-white cloudy ice. It also melts more slowly than cloudy ice: this can be a positive or negative aspect depending on how quickly you want to cool your cocktail. Aesthetically, however, clear ice is drastically superior to the cloudy stuff and elevates the experience of drinking a beverage with it.
Technically, the world’s best champagne tastes the same whether you sip it out of a Styrofoam cup or from an elegant crystal flute, but the latter vessel might cause you to slow down and appreciate it more. Good ice can do that for your drink as well.
This book is mostly about how to make clear ice via “directional freezing,” a simple trick to force water to freeze into ice from one direction to another rather than from the outside in, as in a typical ice cube tray. When we use a directional freezing system, mimicking how a pond or lake freezes naturally, the ice tends to form in perfect clarity as it pushes trapped air and impurities away from the point of freezing.
I didn’t create directional freezing, but I did help translate the natural process to the home freezer. More than a decade ago, after many months of experimenting with making clear ice, I figured out that you can imitate how a pond freezes by putting water into a hard-sided beverage cooler, leaving the top off, and placing it in the freezer. Back in 2009, I shared my technique, and although top bartenders around the world began adopting this method to make clear ice cubes, it wasn’t until YouTubers and Instagrammers began posting how-to videos of the process that it really took off.
In the years since my blog post, an army of ice nerds has joined me in finding beautiful and fun new ways to make ice in a variety of shapes, bedazzling it on the inside and out, and generally increasing the awesomeness of everyday ice cubes. So I can’t take credit for all of the good ideas presented here: just the one Big Idea that inspired the rest. It is my pleasure to share with you some of my favorite manifestations of frozen water.
An Ice Odyssey: How I Figured Out Directional Freezing
Do you remember being told that you should boil the water to make clear ice? When I was a kid, there was even an educational segment between cartoons on TV that told us this. It was science!
But it was all a lie. The boiled water urban legend is something everybody “knows” and yet very few people have fact-checked.
In the early days of the post-2001 craft cocktail renaissance, some bars began making larger ice cubes than the ones made in ice machines to put into slow-sipping drinks like the Old-Fashioned. They froze water in large containers and then cut up the blocks into big cubes by hand. (This was before you could buy 2-inch silicone ice cube trays.) The ice was not clear, but bartenders tried to improve it by boiling the water first. Others melted down small clear cubes from an ice machine with hot water and refroze them.
I heard about this quest for clearer ice and decided to do some home experiments. I boiled water and then froze it. The idea is that if you boil the water all the air inside the water will bubble off. It doesn’t work, and the resulting ice is still cloudy. Thinking that perhaps the water was reabsorbing air when it cooled down after boiling, I tried putting airtight lids on containers of boiled water and froze that, but this also produced cloudy ice.
Then I tried letting ice melt and freezing it again to see if the clarity would improve. I repeated this with the same water-filled container every day for nearly two weeks. It didn’t get any clearer. Next, I compared frozen distilled water with tap water. Nope. I even froze carbonated water just in case that would magically make clear ice. It does not.
Throughout these experiments I used many different shapes and sizes of containers in which to freeze the water. I started to notice that the ice near the outside of each container was clearer than that near the middle. This was true in round vessels like deli soup containers and in flat square ones like lasagna pans. And it didn’t seem to matter whether the water was boiled, melted, or distilled.
I figured out that if you wanted to harvest just the clear parts of the ice, you could use a wide, flat container to make the ice and then cut off the clear outside edges. Further, I noticed that if you didn’t let the container of water freeze all the way solid, the outside shell of ice was clear, while the center was still (also clear) liquid. It was only when the middle froze solid after the outsides did that the cloudy part appeared. It seemed to me that the cloudy part of the ice was due to “trapped” air in the middle of the ice block. It is the same in ice cubes made in a tray—the outsides are usually clear while the centers are cloudy.
I tried to release that trapped air in the center liquid so that I would have only clear ice. I inserted a metal straw into the middle of a water-filled container so that the air could escape as the water froze. Instead, the water inside the straw also froze and blocked the air from exiting. I tried a few other configurations, but I couldn’t figure out a way to release the air from the middle of a block of ice while it was in the process of freezing.
I theorized that if there were no “middle” of the ice block, then the air couldn’t be trapped there. So I tried freezing water in very thin layers, but there was still a cloudy middle to each layer of ice. I ended up with thinly striped ice with white and clear layers.
I knew I was stuck with cloudy ice. But then I had the thought: If we can’t eliminate the cloudy part of the ice block, could we at least relocate it? The last part of the ice to freeze, the center, is where the cloudy ice forms. But if I used an insulated container, I might be able to control which part of the ice froze first and last.
In theory, I could use an insulated cooler, put it in the freezer filled with water, and leave the top off. As the cooler is insulated on the bottom and sides, the water inside it would freeze only from the exposed top surface downward toward the bottom, then the last part of the block to freeze would be on the bottom of the cooler rather than in the middle. There would still be a cloudy part down at the bottom, but it might be easy to separate from the clear part.
I first tried a soft-sided insulated picnic bag cooler in my freezer, leaving the top open so that it would encourage freezing from the top down. It worked! The top part of the block was perfectly clear and only the bottom was cloudy. But as the bag was made of a flexible material, it expanded as the water froze, and I struggled to remove the ice.
I bought a small, hard-sided cooler to solve that problem and made the same type of clear-on-top ice block. In December 2009 I posted the results on my website. I had discovered the practical way to make clear ice at home. It became known as “directional freezing.”
With this technique, people at home could harvest just clear ice and leave the cloudy part behind. Over the next months and years I was able to refine the technique and figure out some of the nuances. But to be honest, I didn’t understand exactly why water froze into ice this way. It was all based on practical observation.
I then read a terrific book: Ice: The Nature, the History, and the Uses of an Astonishing Substance by Mariana Gosnell. In the first chapter, the author watches a lake freeze and consults with scientists about what is happening. I’ll skip most of the details because it’s surprisingly complicated, but the author describes the way in which water turns into ice and how it behaves while in the process of freezing.
When fast-moving water molecules slow down and form solid ice crystals, the crystals reject air and impurities due to their size and structure, and those impurities and air get pushed away from the point of freezing. Lakes that freeze slowly are clear, as pure ice forms on the surface of the water and grows downward. The air and impurities in the water are pushed below the forming clear ice.
When water freezes fast, though, the crystals grow quickly and surround some of the air and impurities in the water, thus trapping them inside. Lakes that freeze very fast tend to be covered in cloudy ice with lots of trapped air and impurities. So in order to make clear ice at home, I knew I’d want to control not only the direction of freezing but also the speed.
I understood how to make clear ice and also why I was able to do so. And I now knew how to maximize ice clarity. This allowed for a whole range of further experiments, including the writing of this book more than a decade later.
Aperol Spritz over a Clear Ice Spear
3 oz (90 ml) prosecco
2 oz (60 ml) Aperol
1 oz (30 ml) soda water
Add all ingredients to a highball glass with a clear ice spear. (Traditionally served in a large wine glass with ice cubes.) Garnish with orange slice.