The ball in a can of Guinness is known as a widget, and its purpose is to replicate the creamy head and surge of bubbles found in a draught pour.
The Science Behind the Guinness Widget
The widget is a clever piece of technology designed to deliver the distinctive Guinness experience outside of a pub tap.
- What it is: It's essentially a small, white nitrogen filled ball that sits inside the can. Although it looks like a ball, it's often shaped like a dome or disc with tiny holes.
- How it works: Canned Guinness is pressurized with both carbon dioxide (CO2) and nitrogen (N2). Nitrogen is less soluble in liquid than CO2, which is key to the widget's function. The widget contains a small amount of beer and dissolved nitrogen under pressure.
- The "Magic Surge": The reference states, "the second the can is opened, the widget does what it has so patiently been waiting to do. It releases the magic surge of bubbles, replicating the draught experience in a can." When you open the can, the pressure inside drops rapidly. This pressure drop causes the nitrogen-rich beer inside the widget to be forced out through the tiny holes. As the nitrogen comes out of solution, it creates millions of tiny bubbles.
- The Result: This rapid release of nitrogen bubbles creates the characteristic cascading effect and forms the tight, creamy head synonymous with a perfectly poured pint of Guinness draught.
In essence, the widget ensures that canned Guinness provides the same visual and textural experience as its tap-poured counterpart, delivering that smooth, creamy finish.
