Instant Ice: How to Flash Freeze Supercooled Water at Home

Pour water from a bottle onto a single ice cube and watch it turn to slush as it lands, building a tower of ice in seconds. The trick, made popular by the YouTube channel TKOR (The King of Random) in its 2013 video Instant Ice – Waterbending In Real Life!, relies on supercooled water: water chilled below 0 °C that has not yet frozen.

What is supercooled water?

Water normally freezes at 0 °C (32 °F), but only if something gets the ice crystals started. Freezing begins at a nucleus: a speck of dust, a scratch in the container or an existing ice crystal. Without one, water can stay liquid well below its freezing point. This is called supercooling.

Very pure water, free of any nucleation sites, can be supercooled at normal pressure all the way to about −48 °C, where ice finally forms spontaneously. Bottled drinking water in a home freezer only needs to go a few degrees below zero for the party trick to work.

How to make instant ice at home

TKOR's method is simple:

1. Put several unopened bottles of purified water in the freezer. In TKOR's freezer, the timing was 2 hours 45 minutes; yours may need more or less, so check a bottle at intervals.
2. Take the bottles out gently. If they are still liquid but very cold, they are supercooled.
3. Place an ice cube in a bowl or dish and slowly pour the water onto it. The cube acts as a seed crystal, and the water freezes as it touches the growing pile.
4. Alternatively, give a supercooled bottle a sharp knock. The shock triggers freezing, and ice spreads through the bottle in seconds.

Using several bottles helps, because some will freeze solid early and others will stay liquid. Unopened bottles of purified water work best, since they contain few impurities to start ice forming too soon.

Why the ice spreads so fast

Once a crystal forms, the water molecules around it have everything they need to join the lattice, and freezing races outward. Not all of the water turns to solid ice, though. Freezing releases latent heat, which warms the remaining liquid back towards 0 °C, so the result is usually a soft slush of ice crystals and water.

Supercooled water in clouds and freezing rain

Supercooling is not just a kitchen experiment. Stratus and cumulus clouds often contain supercooled droplets, which freeze on contact when an aircraft flies through them, creating dangerous airframe icing. Freezing rain forms the same way: drops fall as liquid through sub-zero air and turn to a glaze of ice the moment they hit roads, trees and power lines.

For more cold-water science, read about the Mpemba-effect question, or see ice growth on a much smaller scale in a rimed snow crystal.

Related reading

• The Mpemba Effect: Why the Experiment’s Definition Matters
• Hot Water in Extreme Cold: What the Pale Cloud Shows
• Soap Bubbles in a Thompson, Manitoba Winter
• Frozen Bubbles at Mount Washington Observatory

Sources