Guinness isn’t just tasty — the company has a long history of technical and scientific innovation.

Guinness draft beer is famous for both its taste and its velvety, foamy head. The creamy foam of dry stouts is notably different from the bitter, more carbonated foam of other beers because of the addition of nitrogen. In fact, kegs that dispense stouts are pressurized with nitrogen, which has a low solubility in liquids and works to displace carbon dioxide (CO₂), imparting a unique head with a pleasant mouthfeel.

The bubbles of other beers, as in lagers, form as dissolved CO₂ comes out of solution slowly. But this doesn’t translate well to canned beers. So, in the late 1980s, Guinness developed an answer: a special can pressurized not just with ₂ but also nitrogen. Cans — and, more recently, bottles — of Guinness contain a floating plastic container called a widget, which releases additional nitrogen when the container is opened. This sophisticated combination has been very successful in mimicking draft Guinness.

In 2006, Guinness introduced another option: the Surger, an ultrasonic device that sits under a pint glass and sends out a pulse of ultrasound to create cavitation, which drives bubbles out of solution.

We cut open a Guinness Bottle to examine how the widget works its magic.

– Adapted from Modernist Cuisine: The Art and Science of Cooking