The magical sight of a soap bubble freezing is one few people have probably ever seen, save for chill-freaks who like to lather up in a walk-in freezer. But it turns out to be a little understood and beautiful bit of science.
In the above video, which has not been sped up,crystals grow and spread their way toward the top of the dome, creating a remarkable snow globe effect.
This effect is caused by a phenomenon called a Marangoni flow, in which liquids move from areas of low surface tension toward areas with higher surface tension, according to new research published in this week's edition of Nature Communications. This causes ice crystals to detach from the freezing front side of the bubble and move around like flakes in a snow globe. Eventually the crystals all grow together and the bubble completely freezes.
But the researchers, led by Jonathan Boreyko of Virginia Tech, found that this only occurs when the bubble and its surroundings are at the same temperature. When a bubble on a freezing surface was placed in a room temperature environment, it only froze midway up. It stayed partially frozen for a while before deflating and collapsing.
So if you really are interested in creating gorgeous soap bubble snow globes, science says you need to commit and do your work in the walk-in freezer after all.