The American Mixologist Online® Newsletter Vol. 11, No. 04 All Rights Reserved
Drinks

Archie Bunker maintained that you don't buy beer, you just rent it for awhile. Well a lot of Americans must be renting these days, because according to Beverage Media, beer remains the favorite alcoholic beverage of men and the second most frequent request of women. Yet despite its popularity, there is a lot about beer you might not know.

For example, when you pop the cap off a 12-ounce bottle of brew, the sudden loss of pressure causes the bottleneck temperature to plunge for a fraction of a second from around 41°F to an incredible -31°F. The nearly instantaneous drop in temperature causes water vapor inside the neck to condense and form a white vapor cloud.

Anyone who's chugged a beer only to have it gush out his or her nostrils knows that beer contains carbon dioxide, a natural byproduct of the fermentation process. When sealed, the internal pressure within a bottle of beer—approximately 30 to 45 pounds p.s.i.—is so high that the CO2 within the beer cannot expand and form bubbles, which explains why no bubbles are visible in a capped bottle. Once opened, the compressed gas in the beer is free to expand and rise.

Greg Bohren, Penn State physicist and beer aficionado, determined that the streams of bubbles actually start as loose clusters of CO2 molecules that require microscopic cracks or pits in the glass to cling to and accumulate into individual bubbles. As they begin to rise from these departure points—called nucleation sites—the bubbles are joined by other CO2 molecules, expand in size and accelerate toward the surface in a steady stream where they will form the head.

In an article in Discover Magazine, Bohren explains why the time-worn habit of adding salt to beer will recreate the head, and contrary to popular belief, it has nothing to do with the chemical composition of sodium chloride. The same results can be achieved by sprinkling any granular substance into beer like pepper, sand or dust. The crystalline structure of the granules create countless nucleation sites for CO2 molecules to cluster and create torrents of bubbles that subsequently collect on the surface as a foamy head.

However, should you feel a need to add a granular substance to your beer, most agree that salt is preferable to pepper, sand or dust.