Guinness fans have long raved about the tight, creamy foam atop a perfectly poured pint (stayed tuned later this week for tips on achieving the perfect pour). That pillow-y effect is thanks to nitrogen, and more and more bartenders are using that strategy on other brews. But what is a nitro-poured beer? 

Beers are bubbly because carbon dioxide builds up during the fermentation process. As the liquid warms, the carbon dioxide "bubbles" out. For most draft pours, extra gas is added to move the beer from the keg to tap.

Nitrogen is even more effervescent (or, for you science-types, less soluble than carbon dioxide in beer). The result is more bubbles. These taps are usually thin and tall with a hole-filled restrictor plate that regulates the gas and brew. The result is a bubbly, cream-like nitro pour. 

While most beers could be poured through nitro taps, low-carbonation varieties are best (think: stouts).

Try it: LoDo's Freshcraft often has a nitro beer on tap (like Bristol's Compass IPA).   

Image by Sami Keinanen