How to make clear ice at home

Tap water carries dissolved air and dissolved minerals. When water freezes, those dissolved substances are rejected by the growing ice crystal rather than absorbed into it, so they get pushed ahead of the freezing front.

In an ordinary tray, the freezing front advances inward from every surface at once. The rejected air and minerals get squeezed toward the middle from all directions, and when the fronts meet in the center the impurities have nowhere left to go. They freeze in as microscopic bubbles, and a mass of tiny bubbles scatters light - which is what you are looking at when a cube is white in the middle.

That trapped air is also why cloudy ice cracks loudly in a drink and breaks up faster than it should. Every bubble is a void, and every void is a place the ice can fail.

Insulate every face except one and the front can only advance in a single direction. The rejected air and minerals are pushed steadily ahead of it, always toward the last part to freeze, and they end up concentrated there instead of being trapped in the middle.

That last-to-freeze zone becomes your sacrificial layer. Everything you did not want is in it, and you cut it off. The rest is water that froze with nothing left in it to scatter light - glass clear, and dense, with no voids to accelerate the melt.

This is the whole idea, and it is also why the folk advice about boiling water twice is mostly beside the point. Boiling removes some dissolved air and does nothing about the direction of the freeze. A cooler with the lid off beats boiled water in an ordinary tray every time.

Here it does, and it is one of the clearer cases on this site. The cooler method genuinely works, and it also involves lifting a heavy block, tempering it, scoring it, splitting it with a mallet, and cutting the results down - every single time you want ice.

An insulated mold replaces all of that with filling a tray and, a day later, popping out four finished pieces. It is not making better ice. It is removing about ten minutes of wet, cold work per batch, and that is the difference between a technique you use twice and a technique you use weekly.

The honest sequence: try the cooler method once, this weekend, for nothing. If you find yourself doing it again the following week, buy a mold. If you find yourself wanting ice you did not plan for, that is the argument for a machine, and molds vs machines is the comparison to read.

Cutting ice is not difficult, but it does have a correct method and an incorrect one, and the incorrect one produces a lot of small fragments and a bad mood.

• Temper first. Five to ten minutes at room temperature. Cold ice is brittle and shatters; slightly tempered ice splits cleanly along a score.
• Score, then split. Draw a serrated knife along the line you want several times to create a groove, then tap along the groove with the back of a heavy knife. Do not try to cut through in one go.
• Tap, do not chop. The split propagates from the score. Force just makes fragments.
• Work on a towel. It stops the block sliding and it catches the meltwater.
• Keep the offcuts. Anything too small for a rocks glass is ideal shaking ice.

Clear ice you made yesterday can be ruined by Thursday. Ice left uncovered in a freezer sublimates - it turns directly to vapor at the surface - which frosts the outside and rounds the edges. It also absorbs odors, and a cube that tastes faintly of last week's dinner ruins a drink far more effectively than a cloudy one does.

Store finished pieces in a sealed bag or a lidded container. If you are keeping them more than a few days, double-bag. And do not store them in the same drawer as anything strongly aromatic, sealed or not.

Serving is the other half of this. Good ice has to survive the trip from freezer to glass, and an insulated bucket is what makes that possible for a round rather than a single drink - see best bar cart accessories.