Crystal maze: The mystery of clear ice

When enjoying a finely made cocktail or sipping on premium whiskey, the little details make all the difference: the aroma of the ingredients added, the feel of the glass in one's hand.

- Swetha Sivakumar

One of the most-overlooked components? The ice.

I mean, it's just water, frozen: you might be thinking. What more is there to say? Well, regular ice is just water placed in a freezer and allowed to set. Which is why it is often clouded with air bubbles and trapped minerals. Clear ice is like a polished gemstone in one's glass, and it adds no tinge of mineral flavour to a drink.

I am not suggesting this is in any way an issue. It just interested me to see the differences—and I recently managed to make clear ice at home. So here's a bit of what I have learnt lately.

Most ice turns out cloudy because, as water starts to freeze in a regular tray, dissolved gases such as oxygen and nitrogen, and minerals such as calcium and fluoride, are pushed inward and trapped. This concentration creates the cloudy, sometimes opaque effect.

Clear ice is made using a method called directional freezing, in which freezing occurs from a single direction (usually top-down), so that impurities are pushed away from the freezing front, into what remains a body of water below.