stout widget

The widget-free way to foamy stout

When pouring a can of stout such as Guinness, the physics behind the satisfying head of beery foam that forms is probably the last thing on most people’s minds. A new study has investigated the phenomenon in depth, and suggests a new technique for bubble creation that could supersede the ‘widget’ — a hollow plastic sphere with a small hole in it — currently used to set some canned beers foaming when opened.

Stouts bubble less readily than lagers or other carbonated drinks when poured because they contain dissolved nitrogen as well as the carbon dioxide that drives the fizz. Adding nitrogen makes the beer less acidic, and gives a longer-lasting head with relatively small bubbles that are behind stouts’ smooth, creamy ‘mouth feel’.

But the addition also demands the use of the widget, which takes in gas and beer as it floats in the canned stout and, when the can is opened and the pressure drops, jets it out again through the hole, helping to create the foam.

The new study, published in the online physics archive arXiv1, suggests that the same result could be achieved by coating part of the can’s interior with cellulose fibres.

“It would be a much simpler process than using widgets,” says William Lee, a physicist at the Mathematics Applications Consortium for Science and Industry at the University of Limerick, Ireland, who led the work.

A fibrous coating might be cheaper and more environmentally friendly than the current practice of injecting liquid nitrogen into cans to pressurize the widget, he says.

Nature: Read more