N is for Nitro
If you’ve spent any length of time in a bar, chances are you’ve witnessed the mesmerising effect of nitro in beer. Cascading up the glass in a reverse waterfall of tiny bubbles, it’s probably most often seen in pint glasses of Guinness. The brewery has even gone so far as to create a gas widget for its can that helps mimic the draft experience, but that’s another story.
Nitro refers to the gas blend that’s used to push the beer out of a draft system – generally comprised of 70% N2 (nitrogen) and 30% C02 (carbon dioxide). C02, the most common gas used in beer dispensing, forms larger bubbles in beer than N2. When a beer is nitrogenated, it leads to very small, fine bubbles and extremely creamy palate. There are two reasons for this.
First, nitrogen is, for the most part, insoluble in liquid (it doesn’t like to dissolve). This makes for that thick mouthfeel and your ability to float various bar items on top of your beer – bottle caps, small coins, etc.
Second, bars use what’s called a restrictor plate in the tap setup. This device forces the beer through very small holes before being poured into the glass.
But what’s up with the reverse waterfall? How can those nitrogen bubbles defy gravity and cascade towards the bottom of the glass?
The answer actually has to do with how the beer flows in the glass. Because most pint glasses are narrower in the bottom than the top, there is more space at the wide, flat, middle of the glass, than under its angled walls. This means there are more bubbles rising from the middle than the sides.
This higher density of bubbles in the middle causes a type of beer fountain. The beer rushes up the middle of the glass and slowly flows down the side – only to be rushed back up the middle. As this happens, the bubbles on the sides of the glass are being pulled down with that beer – seemingly defying the laws of physics.
Explain that to your buddies at the next pub crawl, and see if you don’t get some awestruck looks!
While Devil’s Peak has yet to nitro a beer, it could be on the cards.
“It’s definitely something I want to try,” says JC, our head brewer.
A nitro’d Russian Imperial Stout from The Taproom? Yes, please!