That clangy thing taking up space in the bottom of your Guinness or Tetley’s can might soon be done away with and replaced by a coffee filter.
The ball inside the Guinness can, called a widget, contains a pocket of nitrogen gas held under pressure. When some lucky person opens the can, the pressure is released and the gas shoots out into the beer through a small hole and creates the foam.
You may now be thinking, Wait a minute—most beers seem to have plenty of gas bubbles even without some fancy widget. The thing is that Guinness and similar brews need the widget because nitrogen bubbles are smaller than those filled with carbon dioxide, the bubbling gas in other fizzy drinks. The small nitrogen bubbles make Guinness’ foam deliciously thick and creamy, but it’s harder to get the gas to come out of solution. The widget forces lots of excess nitrogen into the beer, setting off a well-timed bubble eruption.
Oh, St. Patrick’s Day! Somehow it has become the day of binge drinking, day of doing shots, and the day before contemplating why you spent the last 24 hours drinking your head off. Nonetheless, St. Paddy must be honored, and honor him we shall—with alcohol and some science.
We decided to reach into the past and pull out the wondrous mystery of the Guinness beer bubbles. For years, the mysterious downward flowing Guinness bubbles have confounded both professional scientists and drinkers. When the bartender pulls a pint of most any beer, the bubbles can clearly be seen gushing to the top. When a pint of Guinness is poured, however, the bubbles slyly cascade down the sides of the glass, while the beer mysteriously maintains its frothy layer on top.
So in 2004, scientists Andy Alexander from the Royal Society of Chemistry and Dick Zare of Stanford University decided to find out why the bubbles act the way they do. After preliminary research trips to the local pub proved unfruitful, they decided to move the scene to a lab where they rigged a high-speed camera to take pictures of the Guinness being poured. The camera could zoom in and magnify the images ten times.