Tech Review reports on some Danish experiments on beer foaming, https://www.technologyreview.com/s/614907/does-tapping-the-bottom-of-a-beer-can-really-stop-it-fizzing-over/ [technologyreview.com] (likely also available on archive.is if you don't subscribe).
Among the great questions in science, one stands sadly neglected: Is it possible to stop a shaken beer can from foaming by tapping it before opening?
There are good theoretical reasons to think this should work. The tapping should release any bubbles that are stuck to the inside walls of the can. These should then float to the surface and dissipate, making the beer less likely to foam when it is opened. But is this true?
Today, we get an answer thanks to the selfless work of Elizaveta Sopina at the University of Southern Denmark and a few colleagues. This group has tested the theory for the first time using randomized controlled trials involving 1,000 cans of lager. And luckily for the research team, the result raises at least as many questions as it answers, ensuring a strong future for beer-related research.
The cans were then shaken using a “Unimax 2010 shaker” for two minutes at 440 rpm. “Pilot testing revealed that this shaking method successfully mimicked carrying beer on a bicycle for 10 minutes—a common way of transporting beer in Denmark,” says Sopina and co. Unwanted foaming must be at epidemic levels there.
The researchers then weighed each can, tapped it by flicking it three times on its side with a finger, and then opened it. Finally, they weighed the can again to determine the amount of beer that had been lost.
The results are palate tickling. Sopina and co compared the amount of beer lost for tapped and untapped cans that had been shaken and found no statistical difference—both lost about 3.5 grams of liquid to foaming.
They also found no meaningful difference between the cans that had not been shaken—when opened, they lost about 0.5 grams on average.
Personally, I don't have a dog in this fight, always drink bottled (or tap) beer. But for you can users I suggest that looking inside the can might be a more direct way to see what is going on with the bubbles--seal up a can with camera & light source inside, or make some cans with a small viewing window. But that might generate an answer, where the goal of this research seems to be to consume more beer...For Science!