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Got Spikes
on Your Ice Cubes?
you are not alone ...

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Why do ice cubes grow spikes?

The short explanation is this: as the ice freezes fast under supercooled conditions, the surface can get covered except for a small hole. Water expands when it freezes. As freezing continues, the expanding ice under the surface forces the remaining water up through the hole and it freezes around the edge forming a hollow spike. Eventually, the whole thing freezes and the spike is left.

A slightly longer explanation: the form of the ice crystals depends on the cooling rate and hence on the degree of supercooling. Large supercooling favors sheets which rapidly cover the surface, with some sheets hanging down into the water like curtains. These crystallites tend to join at 60 degrees and leave triangular holes in the surface. Hence, spikes often have a triangular base. The sides of the spike are sometimes a continuation of pre-existing subsurface crystallites, and can extend from the surface at steep angles.

Pictures of spikes on ice cubes:

With very cold (-10C to -20C) freezer conditions, spikes will often form during the rapid freezing of ordinary ice cubes. In a frost-free freezer, the kind that most people have, initially sharp spikes will take on a rounded appearance as they slowly sublime away.

Movies of growing spikes:

Spikes in the great outdoors:

Spikes are occasionally seen in a natural setting. Since rapid freezing under supercooling is required, they are usually the result of someone leaving a relatively small volume of room temperature water outdoors overnight.

Links to other pages about spikes:

References:



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Go to the Nonlinear Physics Group home page

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The Experimental Nonlinear Physics Group, Dept. of Physics, University of Toronto,
60 St. George St. Toronto, Ontario, Canada, M5S 1A7. Phone (416) 978 - 6810