How many individual bubbles are in a “typical” beer head, and if left alone, how long do they last before popping?
I’d say it depends on the beer. At tastings one thing you note is the size of the bubbles (the smaller the better) and how long the head lasts.
Even the desired bubble size varies. For a stout, it’s usually very fine - so the head is creamy. But for an ale, an open, frothy head is quite normal.
1…2…3…Gulp
Th-r-r-ee.
From personal observation while on a work trip to Darmstadt: Based on the time that a German bartender waits for the bubbles to subside, so that he can top it off and give you a legal pour, three to five agonizing minutes.
This calls for massive study before chancing a conclusion.
Anybody willing to finance such an in-depth examination of the topic? I estimate it shouldn’t take more than a few decades of research.
There are quite a number of different variables that will change how much head, size of the bubbles in the head, and how long the head lasts. Some of the biggest are: Proteins in the beer, carbonation level (amount of dissolved gas in the beer), gas used to draw the beer from the keg, how rough the pour is and the temperature of the beer.
For example, a hefeweizen (unfiltered wheat beer) has a lot of protein in the beer because of the wheat used in making it. Similar to how urine foams when you have a lot of dissolved proteins in it, it foams heavily. (Don’t use this explanation in a bar)
Many beers are also carbonated at a higher or lower rate than others and that will change how much head you see as well. A highly carbonated beer, such as a hefeweizen, will have a huge head compared to, for example, a much lower carbonated Wee Heavy.
Different gas mixtures result in different sizes of bubbles in the head. Compare a stout poured with nitrogen to a stout poured with CO2. With the nitro you get huge quantities of small bubbles and, as a result, a very thick, creamy long lasting head. With CO2 there are fewer, larger bubbles.
If you are pouring out of a bottle the roughness of the pour will change the size of the head. Take two beers, pour one gently down the side of the glass and pour the other quickly down the center of the glass. The gentle pour will have nearly no head while the rough pour will be overflowing the glass. This is why you should never drink beer out of the bottle (or can) and why beer on tap tastes better to most people. Most of the aromatics show up when the bubbles in the head begin to burst so a bad pour (or no pour) keeps you from enjoying a lot of the flavor and aromas.
Lastly, temperature has a huge effect on the size of the bubbles and the amount of head. A cold beer will have less head than a warm beer and, what’s more, the head will last much longer on the cold beer.