Scientists solve Guinness mystery
Published 17/03/2010 | 05:00
IT'S not the work of mischievous leprechauns or the result of having one too many -- Guinness bubbles really do go down instead of up, say scientists.
Pour just about any other pint of beer and the bubbles rise to the surface and form a frothy head. But not Guinness.
Members of the Royal Society of Chemistry in London set out to investigate the puzzle. The scientists used a super-fast camera that could zoom in and magnify the bubbles 10 times.
The study showed that the more visible outlying bubbles in a pint of Guinness did move downwards, as a result of circulation flow and drag.
At the centre of the glass, the bubbles were free to rise rapidly, pulling the surrounding liquid with them and setting up a circulating current.
Dr Andrew Alexander, who led the researchers, said: "The circulation cells in the glass provide the same effect as you see in a tornado."
A spokesman for the RSC said: "We're pleased to have solved this mystery in time for St Patrick's Day, when many people will enjoy a pint or two."