Bubble Trouble

Am I tipsy, or are my beer bubbles….sinking?!

This is Sandra Tsing Loh with the Loh Down on Science.

Fans of the Irish stout, Guinness, are perplexed. The bubbles in their pints seem to…. sink!

William Lee, a mathematician at the University of Portsmouth has BURST this case wide open! Lee and colleagues developed a series of equations to explain the bubbles’ rebellious behavior.

It starts with size. In most carbonated beverages, the bubbles are pure carbon dioxide. But Guinness also includes nitrogen gas, which makes bubbles ten times SMALLER than carbon dioxide. Size matters!

Lee accounted for these smaller bubbles in his mathematical model. And here’s what he learned:

After you pour yourself a pint, the SMALL bubbles STICK to the glass’s outer edge. Meanwhile, LARGER bubbles float upwards, but they’re hidden from view in the CENTER of the glass. Once at the pint’s peak, the upward flow of liquid is forced back downwards. This current sweeps the small bubbles DOWN, sinking them before they can float back up!

So, when it comes to Guinness, what goes DOWN must come UP! And that ain’t just the beer talking, mate!