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Tiny Bubbles


Beer is unique in many ways but perhaps the most outstanding from a visual perspective is that it is the only beverage that forms a stable “head” or foam top.  I love a nice foamy head on a beer and I know for a fact that the presence of the head makes the beer underneath it taste better.

What’s in that head?  Where does it come from, why is it important, and how much is the right amount?  Why do bubbles continually stream up from the bottom of the beer? Why are there rings around the glass when you’re done? And why are there sometimes a profusion of bubbles sticking to the inside of the glass?  Hopefully I can answer these questions, and I’m going to do my best to do it without using terms like “nucleation site” or “Sigma value.”

The head is formed when the beer is poured into a glass and some of the carbon dioxide that is dissolved in the beer comes out of solution.  There are proteins (derived from malted grains) and resins (derived from hops) that allow stable bubbles to form.  Many beverages have different sorts of protein in them but do not form foamy tops: hops are key.  No hops, no head. 

The bubbles aren’t just filled with CO2, though: all sorts of other aromatic compounds go in to the tiny little bubbles along with CO2.  As those bubbles sit on top of the beer, some of them burst, releasing those aromatic compounds right under your nose.  In a well-made beer, bubbles continually rise from the bottom of the glass restoring the head even as the top bubbles burst under your (hopefully appreciative) nose.  This is critical to enjoying the flavor of beer because the vast majority of our perception of taste comes from our sense of smell.  The taste buds on your tongue can only detect five very basic flavors; the rest of your sense of taste really comes from the interaction of those flavors with your sense of smell.

Bubbles continually rise from the bottom because there isn’t enough CO2 pressure in the atmosphere to keep them in solution in the beer (and that’s a good thing: that much CO2 in the atmosphere would kill you.)  CO2 likes to come out of solution wherever there is a microscopic scratch in the glass or a particle of some kind.  Some people like to put salt in their beer to liven it up—all the little salt crystals give CO2 many places to come out of solution.  Some glassware (especially that intended for sparkling wine) is intentionally scratched or etched to give CO2 a place to come out of solution.  If you can find one, look at the bottom of a Chimay glass: it has a small “fleur de lis” etched in the bottom.

One of the coolest looking consequences of a foamy head on a well-made beer is the foam that clings to the inside of the glass, sometimes forming rings.  This is known as “Brussels lace” and is one sign of a well-made beer.  Since hops contribute to head formation, you are likely to see more lacing after you’ve enjoyed a hoppy beer like our HopStorm IPA.

When you receive a fresh, well-made beer it should have a dense foam head on it about the thickness of an average index finger, you should see a steady stream of bubbles rising from the bottom of the glass, and there should be no bubbles clinging to the inside of a glass.  Remember that CO2 is picky about where it comes out of solution and prefers to have a scratch or particle of some kind—if the inside of the glass has bubbles clinging to it, chances are good that the glass was not properly cleaned and the CO2 is showing you where the dirt is.  You should never see that in BJ’s, but if you do, please send the beer back. We want you to enjoy our beers at their best, in a clean glass, with a nice foamy head on top. Our goal is to serve you the perfect pint, every time!



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