How freezing a soap bubble turns it into a ‘snow globe’
Differences in surface tension create currents in soapy films that move ice crystals around
THIN ICE A patchwork of ice crystals swirls across the surface of a soap bubble as it freezes. The glittery display is caused by a mismatch in surface tension in different regions of the soapy film.
F. Ahmadi, C. Kingett and J. Boreyko
Frigid air can transform an ordinary soap bubble into a glittery “snow globe.” No shaking required.
When a bubble is placed in a freezer set to –20° Celsius, delicate ice crystals swirl gracefully across the soapy film, gradually growing larger until the bubble freezes solid. The phenomenon can also be observed when blowing soap bubbles outside in wintry weather. Although the process is captured in a number of YouTube videos (see examples here, here and here), it lacked a scientific explanation. Researchers from Virginia Tech in Blacksburg explained the physics behind the miniature snowstorm on November 20, during the American Physical Society Division of Fluid Dynamics meeting
