Glossary
Clear ice
Ice frozen directionally so air and minerals are pushed out, giving a dense, slow-melting cube that looks glass-clear.
Clear ice is ice that freezes without trapped air bubbles or mineral cloudiness, made by controlling the direction water freezes in so that impurities get pushed ahead of the ice front instead of getting trapped inside it. The result looks like solid glass rather than the cloudy white center found in ordinary freezer ice cubes.
It matters for two reasons beyond looks. A denser, bubble-free cube melts more slowly than a cloudy one of the same size, so it dilutes a drink less over time, and it also cracks and shatters less easily when stirred or dropped into a glass, since trapped air pockets are usually where cracks start. That combination makes it popular for spirit-forward drinks served on the rocks.
Dedicated clear ice makers use directional freezing, insulating a container on most sides so freezing only happens from one direction, pushing impurities down and away from the final block. A common mistake is expecting any large ice cube tray to produce clear ice, when the shape alone does nothing without controlling which direction the water actually freezes from.