COFFEE spills more easily than beer, and physics can explain why.
Carrying drinks from the bar, Alban Sauret at Princeton University noticed that beer rarely sloshed out of a glass, provided it wasn鈥檛 full to the brim. The same was true of a latte, though less so, but not a regular coffee.
To investigate, he and his colleagues mixed water with glycerol and surfactants and blew bubbles to create a stable foam. The mix allowed them to control the size of the bubbles and the thickness of foam. The team jolted containers holding liquids covered with different foams and filmed their sloshing motion, then analysed the video to study how the velocity of individual bubbles related to the foam鈥檚 dampening abilities.
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It turns out just 0.3 centimetres of foam is enough to of the sloshing motion, and 3 centimetres stops it almost completely, Sauret told the at a meeting in San Francisco this week.
The study started as pub talk, but may have useful applications in keeping hazardous fluids from spilling over.
This article appeared in print under the headline 鈥淏eer has its own anti-spill mechanism鈥�