If you're not in a bar, the Guinness can (rather than the bottle) is the best way to approximate the flavor and experience that is particular to the pub tap. G

If you're not in a bar, the Guinness can (rather than the bottle) is the best way to approximate the flavor and experience that is particular to the pub tap. Guinness put 20 years of research into the can method. The 16.9 ounce can (containing 14.9 ounces of beer) is fitted with a small plastic device (Guinness calls it a "smoothifier") which sits in the bottom of the can. This device has a pocket or cavity which is open to the atmosphere via a pin hole in its top. The can is evacuated of oxygen and filled with beer. Prior to sealing the can, a dose of liquid nitrogen is added to the beer. The can is closed and as the liquid nitrogen warms a pressure is created. The pressure forces about 1% of the beer and nitrogen into the plastic cavity. When the can is opened, the pressure is released and the small amount of beer in the cavity is forced back through the pinhole quite violently. The agitation created by this "geyser" mixes the nitrogen with the beer in such a way as to reproduce the tap handle character. Prior to serving, the beer must be chilled. Guinness suggests a two hour stint in a refrigerator, with a target serving temperature of 45-50 degrees (if opened while warm, the beer gushes with excess force). This is the one area where flavor will be variable since most American refrigerators hold their temperatures closer to 35-40 degrees. The colder the beer, the less the flavors are perceptible. The entire contents should be emptied into a 16 ounce glass. The head which forms is exactly like that of the draught version. It should last to the bottom of the glass.