What does a rocket widget do in a Guinness beer?

Answer 1

To really understand what the widget does, first you have to understand how Guinness is served on tap.

Guinness is a beer with relatively low carbon dioxide content. Low CO2 beers generally have gas added to them as they're released from the tap (called brewgas - a CO2 and nitrogen mix usually), which gives a thick, creamy head to the beer. The head is very important for flavor and texture of the beer. Guinness in particular needs a half-inch head to get the optimum "creaminess." Normally, it's not possible to add the brewgas to a canned or bottled beer; it has to be added just before pouring to agitate the beer and make a thick head.

Canned Guinness solves this problem using a "widget" - a plastic ball that holds some brewgas inside it. When you open the can, the change in pressure forces the gas out of the ball. The extra shot of gas, combined with pouring it into a pint glass, causes it to develop the same head that it would in the pub. (Guinness cans actually have instructions on the side, telling you to pour the beer instead of drinking from the can.)

The rocket widget is essentially an improved version of the ball widget. It still gives the initial burst of brewgas when the bottle is first opened, but the new design gives an additional "squirt" of gas each time the bottle is turned upward, recharging the head each time you take a drink. The result is that you can drink Guinness straight from the bottle, without sacrificing the head and impacting the flavor.