United States Patent  5,863,577 Lynch , et al. January 26, 1999 A beverage package and a method of forming such a package defines a primary chamber containing an insert defining a secondary chamber. The insert has a seating in the form of a bore within which is received the lower end of a tube which is fitted to the insert. When the package is charged with beverage such as beer having gas in solution and sealed to form a headspace containing gas at a pressure greater than atmospheric, beer from the primary chamber fills the tube. The secondary chamber contains beverage and gas at a pressure greater than atmospheric and on opening the container the headspace depressurises
	causing beverage and gas from the secondary chamber to be ejected through the tube. A restricted aperture between the bottom end of the tube and an opposing wall of the insert causes froth to be developed in the beverage in the secondary chamber as the beverage flows into the bottom end of the tube. The frothy beverage then flows through the tube into the headspace. The tube isolates a major part of the beer in the container from having its gas liberated so that such gas can evolve gradually to provide sparkle in the beer when the latter is poured into a glass.
	THAT sounds complicated! The picture associated with the cited patent reflects something just as monstrous. Odd, considering that all I've ever noticed in the can is something sort of like a little bathysphere. So, to quell my curiosity and, hopefully, that of many of you, I have sent the HBD Labs forces out to dissect a Guinness can. What follows may be consider vivisection to those in the packaging industry. If you're squeamish, please: don't come any further along this path to discovery. For the rest of you, follow me!