> wrote in message
...
>
> : You don't shake the beer, but the empty can rattles - it contains a
hollow
> : ball filled with nitrogen, that has one or two tiny perforations in it.
When
> : you open the can (or relatively 'flat') beer, the escaping nitrogen give
a
> : fine beaded creamy head, quite unlike the large bubbled one produced by
> : carbonated beers.
>
> It's not a ball. It's a round disk.

It used to be a disk; it's a ball in the Guinness cans now.

kili