As the icicle turns

Canadian iciclologists have discovered the perfect conditions to grow smooth uniform icicles – pure water and a breeze, anything else results in lumpy structures with offshoots.

Stephen Morris and Antony Szu-Han Chen’s findings challenge the accepted notion that all icicles should, by and large, assume a conical shape and that still air is necessary for the perfect icicle.

The pair – from the University of Toronto – used a refrigerated box with a water drip at the top to grow icicles 50cm in length under different conditions.

“As far as we know, no one has really systematically studied the shape of icicles and how they grow,” Morris said, “Nobody has really tried to fill in the physics of how the shape emerges.”

The structures were rotated once every four minutes so that, on average, the whole surface got the same treatment with the results recorded on film.

The iciclologists discovered that icicles grown from tap water and in still air were lumpy and sprouted shoots at the tip, and they believe impurities in the tap water may be responsible for the rippled shapes. Icicles grown in moving air and with distilled water assumed the traditional smooth conical shape.

Morris said understanding how icicles for is important for engineering problems such as ice on the wings or airplanes or on power lines: “If you can’t understand and icicle, you’re not going to understand how ice develops on a fast blowing airplane wing,” he said.