Crystal clear ice may not make your cocktail taste any better, but it definitely makes it look more elegant and sophisticated. Using a process called directional freezing, you can make a huge batch of perfectly clear ice without any expensive equipment. In this video from the Cocktail Chemistry YouTube channel, you'll learn how you can use it to create glass-like ice that can be shaped for multiple styles of cocktail. All you need is a small cooler with the lid removed, and a serrated knife and mallet for carving the ice. Fill the cooler with water (tap water is just fine), then stick it in the freezer for about 24 hours. It should be crystal clear ice by that time. Then plop the clear ice block on a cutting board and get carving. You can make small ice cubes for general use, large cubes for whiskey and long cubes for cocktails in tall glasses.
As the video explains, the cloudiness you see in most ice is formed toward the end of the freezing process. Directional freezing in an insulated cooler -- a process originally developed by Camper English at Alcademics -- forces the water to freeze top to bottom, which keeps the water in the cooler from freezing all the way through. In fact, you don't want the water to freeze all the way through because that's when the impurities begin to form. Using filtered or boiling water will help with cloudiness to some extent, but this method will guarantee maximum clarity.
Cocktail Chemistry - Clear Ice [YouTube]