Normal ice trays freeze their cubes from every angle at the same time. This locks in air bubbles, impurities, and all the little particles that make ice cloudy. Directional freezing only allows ice to freeze from the bottom up, in one direction. This gives all the air bubbles and particles time to escape through the top. Ever see a pond that’s partially frozen? The top layer is always super clear because it freezes from one direction (the air above). This is the same thing!
Some of the directional ice cube trays empty like normal trays where you shake or “crack” the ice out, while others have a latch you pull or a lid you open to unlock the ice. The size of your ice cubes can influence how long it takes to freeze. If you have one of those big ice trays to make spherical ice cubes, it may take 6-8 hours.
The double-boiling method will not give you perfectly clear ice, but it’s going to be as close as you can possibly get without using a directional freezing method. If you really want your ice to be as clear as possible, use distilled water for this.
Boiling the water twice ensures that you’ll evaporate any impurities that weren’t fully dissolved the first time you boiled the water.
Again, you may still have some cloudiness in your ice, but your cubes will be way clearer than they would be if you just filled up the ice tray with tap water and tossed it in the freezer.
The cooler method is the only consistent way to directionally freeze ice at home without a special ice tray. You do need a lot of space in your freezer though, and your cooler has to be perfectly clean for this to work.
The more water you add, the more ice you can make. However, it’ll take a lot longer for a full cooler to freeze than it would take for a few inches of water to freeze.
You can remove the ice at any point once the top layer is frozen. Keep in mind that the more water underneath the top layer, the easier the ice block will be to handle.
Wear a thick glove on your non-cutting hand to hold the ice still and keep your hand warm. The ice at the very bottom of the cooler will be very cloudy. It’s perfectly fine to use if you’d like, but the top layers of the ice will be the only clear ice.
