By Devin Powell
This St. Patrick’s Day, raise a glass to the beer researchers of Ireland. By figuring out how bubbles form in stout beers, a team of mathematicians has come up with an idea that could better unleash the foamy head of Guinness: beer cans lined with a material similar to a coffee filter.
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Stout beers foam less than other beers when poured, thanks to the nitrogen gas that brewers inject into the liquid before packaging. Nitrogen cuts down on acidic tastes and provides a longer-lasting head and a creamier mouthfeel, owing to the small size of its bubbles. But nitrogen doesn’t dissolve as well as other gases or form bubbles as easily. That’s why bars need special devices to force the bubbles out of tapped stout beers and why every can of Guinness contains a hollow ball filled with nitrogen gas that triggers foaming. It’s also why beer aficionados in search of a foamy head spend 30 seconds on the perfect pour.
Carbon dioxide, present only in small quantities in stouts, gives a quick fizz and foam to soft drinks, champagne and paler beers. Pour a bottle of one of these carbonated beverages, and the gas readily comes out of the liquid. Bubbles speedily form and grow larger while rising through the liquid, adsorbing gas and releasing it at the surface.