What is that little plastic thing in cans and bottles of Guinness?

That little piece of white plastic is referred to as a widget and carries a small charge of nitrogen gas that give your Guinness some fizz and head (the white foam on the top). Most beers are carbonated with carbon dioxide (CO₂₎, which is a natural byproduct of fermentation. This is quite convenient because yeast provides the carbonation.

Guinness Draught is a less carbonated stout and porter hybrid; yet, it still retains a thick frothy head, which is a difficult task, especially for cans or bottles. This is accomplished with a lower carbonation of carbon dioxide and inert nitrogen gas (N₂).

Fast-forwarding past the gory details of gas dissolution --if you really want them, send me an e-mail-- I'll use an analogy. Imagine a can of beer, and we'll represent the liquid as round rocks. In between these rocks, there are small crevices. It is simple to push some smaller rubbery pellets (they'll represent carbon dioxide) into these small crevices. If you really squeeze and push these rubber pellets in as tight as they go and apply a lid, the can will be under pressure-- exactly how most cans and bottles of beer come. When one opens the can or bottle, some of these pellets come spilling out of the gaps to the top due to pressure, creating bubbles and a nice head on a beer.

Now Guinness is another story because they don't want nearly as many pellets (carbonation) in the beer, but they still want some pellets to push their way to the top to create a nice thick head and a few bubbles for a tingly feeling on your tongue. The widget and the nitrogen gas allow for this. Imagine the nitrogen gas as hard balls, similar in size to the carbon dioxide rubber pellets. But the little balls want to get out of the rocks, also known as liquid beer. They hate spending time in the crevices and want to get into that space at the top of the can. In essence, the widget holds a charge of small hard balls or nitrogen gas, so that when the can is opened, it pushes some of the rubber pellets, carbon dioxide, up and out to create the bubbles and give Guinness its trademark thick, frothy head. Most of the nitrogen gas escapes to the air. If the widget didn't hold the gas, it would just sit at the top of the can and release out the top upon opening, leading to a flat Guinness pour.

The widget allowed Guinness to bring draught quality beer to cans in 1988 and a 1999 modification of the spherical widget, called the rocket widget, allowed the introduction of Guinness Draught in bottles. In 1992, the widget was awarded the Queen's Award for Technological Achievement. This ingenious invention has allowed Guinness to offer its beer in a convenient take home package, allowing Irish Carbombs to be enjoyed in fraternity houses, apartments and dorms throughout State College and elsewhere.

A few other brewers have adopted the widget but Guinness is certainly the most well known.

NOTE: Guinness had made attempts to launch its Draught before the widget was invented with other methods but to limited success in matching the quality of its true tavern quality Draught.

Chris Straub is a senior majoring in Chemical Engineering. He is also the great-great grandson of the founder of Straub Beer. His e-mail address is cts150@psu.edu