Beautiful crystal clear ice cubes, tailored in size and shape to the glass and drink, are a great way to elevate your cocktail service. You often see these kind of cubes at high-end bars, but how can you achieve this at home? It’s easier than you think.
Large format ice cube trays available at most kitchen supply stores work just fine, but I prefer the directional freezing method. The name may sound complicated, but the process is very simple. It creates gorgeous cubes that are crystal clear and can be cut to your preferred dimension. I first read about directional freezing in Dave Arnold’s excellent cocktail book, Liquid Intelligence, but apparently credit is due to Camper English. It’s easy to pull off and just requires some space in your freezer, or a cold winter.
Why Is Regular Ice Cloudy?
Cloudy ice doesn’t come from impure water, but oxygen and carbon dioxide dissolved in water. These normal atmospheric gasses come out of solution as the ice freezes. In regular ice cube trays or ice makers, the ice forms from the outside in, trapping water with increasingly high concentration of gas in the middle of the cube. When the innermost portion freezes, a lot of gas is forced out as bubbles that are literally frozen in place.
What is Directional Freezing?
Directional freezing is the fastest and most efficient way to keep your ice from getting cloudy. It’s simple, requires very little investment, and it’s actually quite fun. The brilliant trick? All you need – in addition to a cold space – is a small beer cooler. Fill it with water and put it in your freezer (or on your porch or window sill covered with a thin towel or saran wrap). Thanks to the insulated sides of the cooler, the water will freeze from the top down. Pull it out of the freezer before it freezes solid, and you have a couple inches of crystal clear ice above some very cold water. In my freezer, 24 hours is about right, but your mileage may vary. And even if you miss the timing and freeze the cooler solid, the top couple inches will be clear and you can cut off the cloudy bottom.
Directional freezing is actually how ice forms in lakes – and before the days of freezers, that’s where all ice came from. If you’ve seen Disney’s Frozen (and who hasn’t?) the scene at the beginning (Frozen Heart) is a great depiction of how ice used to be harvested. After harvest, super-insulated ice houses could keep ice frozen all summer long.
Making Your Crystal Clear Ice Cubes
Now that you have a cooler with a hefty chunk of ice in it, invert it over your sink and wait patiently for your giant block of ice to drop put. There’s likely to be residual water – potentially a lot – so the sink or a roasting pan is a good idea here. Once it drops out, cut off any excess, and then shape your cubes. I find the process of cutting ice magical.
Ice is quite easy to cut, but you have to wait for it to warm a little. Fresh from the freezer, it will be a little gray. Once it’s ready – or tempered – it will turn perfectly clear and have a little moisture on the surface.
To cut ice, use a bread knife you don’t love to score it on all sides, then tap the back of the knife gently with a wooden mallet of some kind (I use a rolling pin or meat tenderizer). You generally get quite clean fractures along the lines you’ve scored, thanks to clear ice’s regular crystal structure. Sometimes though, there are some irregularities, and you can get some funky breaks. It still looks lovely, though.
First cut off any excess. If you timed it right, you just have a 2-3″ layer of ice, but until you get the hang of how long this process takes, you may have either a block of ice with a pocket of water in the bottom third, or a solid block of ice. Sometimes the ice at the bottom is thin enough to simply break off, but you may need to score and cut off part of the bottom. If it did freeze solid, start cutting well above the cloudy bottom portion. You can use the ice you cut from the bottom of the block, but it won’t look as nice and won’t cut cleanly.
When you’re left with a block of ice a couple of inches think, score and cut it into rectangles and then cubes of your preferred dimensions. You get about a dozen 2″ cubes out of a 6 can cooler – depending on what you drink and how often, a batch can last quite a while.
These ice cubes will astonish anyone observant enough to notice them. And when your guests do notice, you’ll feel a gentle glow inside.
Alternatives to Directional Freezing
Some people try to filtering water before freezing it, but as it’s not impurities that create cloudy ice, but dissolved gas, that doesn’t really work. Boiling the water does, though. You may recall from chemistry class that the solubility of gas in water decreases with increasing temperature. As you boil water, you clear most of atmospheric gas out of it. Then pour your freshly boiled water into your ice cube trays and carefully transfer them to the freezer (the water is obviously still very hot!). Gas will dissolve back into the water as it cools, but there will still be less gas in your water when it freezes than there would be ordinarily. Less gas means clearer ice. Still, you’re wasting a lot of energy and time relative to directional freezing.