![]() Poor conduction stopped the freeze front from climbing more than halfway up the bubble. So the researchers didn’t see any ice crystals break off from the freeze front or whirl around the bubble. They were cold at the point of contact with the stage and warm on top. The soap bubbles already had an externally imposed temperature difference. They found that the Marangoni currents were weaker when the surroundings were at room temperature. Boreyko’s team placed soap bubbles on an icy stage outside their walk-in freezer. Could they learn to tweak Marangoni currents to speed up or prevent liquids from freezing?ĭr. The researchers wondered how this phenomenon affected bubble behavior at different temperatures. That results in Marangoni currents that produce swirls of liquid and ice crystals, resulting in a dramatic snow globe effect. In a bubble that’s slowly freezing, the changes in temperature change the surface tension, too. The phenomenon of the Marangoni current also explains why food dyes disperse in a bowl of milk and create a tie-dye effect when you add soap, or why wine appears to leave “tears” behind in your glass as you drink: Liquids move from areas with low surface tension to areas with high surface tension. ![]() The study could also have applications for flash freezing food, creating tastier ice cream or even developing antifreeze materials. Boreyko and colleagues’ results, published Tuesday in Nature Communications, make for fascinating viewing. “We’ve seen the unique freezing dynamics of bubbles in nature, but we’ve never understood the physics behind it,” said Jonathan Boreyko, who studies condensation and frost phenomena at Virginia Tech.ĭr. Recently, scientists set out to explain the transfer of heat that affects how bubbles freeze. So when soap bubbles freeze, lacy crystals break off from cooler points on the surface and swirl around on currents of warmer liquid. Unlike water droplets, puddles or other liquid surfaces, the thin, rounded shape of bubbles makes them poor heat conductors. They’re magical, turning into ethereal globes filled with ice crystals when the surrounding temperature is just right. You may have seen the viral videos of photographers freezing soap bubbles during a recent Snowmageddon.
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