I DIDN’T KNOW THAT...

Q: Why do Guinness and some other European beers have a small plastic ball inside the can?

A: The purpose of the ball, called a widget, is to give the beer an acceptable head when it is poured. Beers are carbonated with carbon dioxide, which is held in the liquid under pressure by the sealed can. When the can is opened and the beer is poured, some of the carbon dioxide escapes, producing foam. Guinness and similar beers, however, contain less carbon dioxide, so engineers have devised a tricky way to produce a head, according to https://www.howstuffworks.com. The widget is a plastic, nitrogen-filled sphere with a tiny hole in it. The sphere is added to the can before it is sealed. It floats in the beer, with the hole just below the surface of the liquid. Just before the can is sealed, a small shot of liquid nitrogen is added, which pressurizes the can, forces beer into the sphere and compresses the nitrogen in the sphere. When the can is opened, the pressure drops and the beer inside the widget rushes out. The agitation releases carbon dioxide, forming tiny bubbles that produce a desirable head.