Ice Blade in Bucket

March 09, 2022

IceSail_20220111_083516 (003)

Photographer: Pierre Renoult 

Summary Authors: Pierre Renoult; Jim Foster

Imagine my surprise when one morning earlier this winter I found a large piece of ice protruding from a bucket of water left out overnight on the terrace of my home, in Aurillac, France. The day before it rained most of the day, and then the sky cleared allowing overnight temperatures to plummet below the freezing point. By the next morning, I couldn’t open my mailbox as it was frozen. This protrusion had an obvious slope and was about 16 inches (40 cm) in length.

Once the sky cleared, fast freezing or “supercooling” of the water in the bucket took place. When water is confined in small places, such as a pool or a bucket, the water freezes first along the edges and so water in the center is slightly raised with respect to the sides. As ice expands beneath the surface it forces out the remaining liquid through the hole at center. This is where the hollow ice blade emerged. Different shapes can be observed, including spikes, sails and needles. The size of the pool of water, just how it’s confined, and differential freezing rates all play a role in determining if protrusions will form and just what shape they'll take.

It’s worth noting that because ice expands in crystalline planes, protrusions commonly occur at similar angles, typically about 60 degrees to the ice-covered surface. If you have a frost-free freezer, maybe you've noticed that sharp spikes sometimes form on ice cubes. Photo taken on January 11, 2022.

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