Just in time for St. Patrick's Day, Irish mathematicians discover a biodegradable alternative to the plastic widget in cans of Guinness.
As St. Patrick's Day draws near, many of you may be anticipating a nice chilled glass of Guinness, complete with a creamy foam head. But if you're not propping up a bar in Ireland, and are instead pouring your beer out of a can at home, that long-lasting head can only be produced with the help of a plastic widget.
Simply pouring a carbonated beer, such as a lager, from the can into a glass is enough to generate a head. But this is not the case for stouts, which are infused with nitrogen bubbles, rather than carbon dioxide, in order to create their uniquely smooth texture. The small plastic widgets in each can of stout contain pressurized nitrogen, which is released once the can is opened, triggering some of the dissolved nitrogen in the beer to bubble up into a head.