Sat. Oct 1st, 2022
Danish physicists have tested 1,000 cans of lager - for science!
enlarge Danish physicists have tested 1,000 cans of lager – for science!

simonkr/Getty Images

Anyone who has fallen victim to the old “opening a shaken beer can” joke has probably heard that tapping the side of the can before opening can prevent the beer inside from fizzing. It’s a nice bit of folk wisdom, but apparently science doesn’t back it up. Danish scientists at the University of Southern Denmark (USD) in Odense tested the tapping strategy and found that it really doesn’t work. They summarize their findings in a recent paper posted to the physics arXiv.

Beer is a surprisingly popular area of ​​research for scientists. For example, there was a 2011 Irish study on bubble formation in strong beers, and in 2016 scientists showed how beer foam reduces the sloshing of beer when poured into a glass, and improves the taste. In 2013, Javier Rodríguez-Rodríguez, a physicist at Carlos III University of Madrid, and several colleagues presented experimental and computer simulation findings about why beer cans froth so much after being shaken, at a meeting of the American Physical Society’s Division of Fluid Dynamics. They concluded that the foaming over came from a series of waves.

“Actually, the laws of physics governing the development of these beer mushroom clouds are the same as” [those that drive] developing the cloud into an atomic bomb,” Rodriguez told NPR’s The Salt at the time. “Obviously, there’s no nuclear stuff in the beer. So the source of the explosion is very different, but the mushroom cloud you see is very similar.”

Video by Javier Rodríguez-Rodríguez, Almudena Casado and Daniel Fuster.

Per Physics Central:

The first tap on the bottle sends a shock wave through the glass to the bottom of the bottle. The energy of the wave is transferred to the beer inside and sends a second shock wave to the surface of the beer. It then bounces back again and continues to move back and forth through the liquid until its energy dissipates.

The wave motion and changing pressure release tiny gas pockets that are trapped in microscopic imperfections in the glass bottle. The bags implode, creating clouds of smaller bubbles from the dissolved carbon dioxide in the beer. While these bubbles can quickly grow up to three times their original size, that alone isn’t what causes the bottle to overflow with foam. Individual plumes of bubbles float up through the beer and build up speed as they get bigger, until they burst from the top of the bottle in a shower of foam.

USD’s Elizaveta Sopina and Elliot J. Brown, co-authors of this latest paper, came up with the idea of ​​testing the hypothesis and possibly ending the horrific scourge of excessive beer spillage. “This is inefficient, as fizzing reduces the amount of beer available for consumption and results in wastage,” the Danish authors wrote of the rationale behind their experiment. “Beer spray can also stain clothing or surrounding objects, and there is also an unpleasant and socially undesirable side effect.”

Whether tapping or tapping a shaken beer helps to reduce fizz and beer loss — though based on reasonable hypothetical assumptions — had never been thoroughly tested, although anecdotal evidence suggested it was ineffective. “Given the strong Danish tradition in brewing and consuming beer, and an emerging trend in exploring alcohol-related urban myths, we wanted to resolve this issue with high-quality evidence,” the authors write.

The experimental setup: cans randomized to the shaker group were claimed on a shaker in batches of three or four.
enlarge The experimental setup: cans randomized to the shaker group were claimed on a shaker in batches of three or four.

E. Sopina et al/arXiv

Over a thousand lager cans were supplied by Carlsberg Breweries A/S for the experiment, although some were excluded due to damage or errors in the experimental process. Finally, on a Friday in May 2018, 1,000 cans were successfully tested. The cans were randomly assigned (using Microsoft Excel’s random number generator) to one of four groups: unshaken/unused, unshaken/tapped, shaken/unused, and shook/tapped. Each can was shaken with an industrial shaker for two minutes, equivalent to what cans of beer would experience if transported for ten minutes on a bicycle (a common way of delivering beer in Denmark).

Three teams then weighed the cans and tapped the side with one finger three times (or not, depending on the group in question). They then opened the cans, “absorbed beer loss with paper towels,” and finally reweighed the cans to determine the beer loss. Initially, the participants opened the cans with their hands, but apparently this caused “finger and nail bed pain,” so they were fitted with stainless steel butter knives to open the rest of the cans.

But tapping the cans was still done manually. The co-authors also considered automating that process, but decided against it, because “the aim of the study was to determine whether this effect would be observable in a realistic use case, not an overdeveloped laboratory setting.”

Graph showing the change in the mass of beer cans by shaking and tapping.
enlarge Graph showing the change in the mass of beer cans by shaking and tapping.

E. Sopina et al./arXiv

The result: The researchers found no significant difference in beer loss between shaken cans that were tapped and those that were not. (The same was true for unshaken cans.) They suggested a possible explanation: The barley proteins in the beer can stabilize the bubbles, preventing them from rising to the top of the can. Further experiments would be needed to determine whether tapping could reduce the fizz of other carbonated beverages, such as soda.

However, one of the teams lost significantly less beer during the experiment than the others. “The most likely explanation for this is that, unlike other teams, Team 3 consisted solely of engineers, who are known to go to great lengths to get the last drop of beer,” the authors wrote. As for the leftover beer, it didn’t go to waste: the researchers distributed the beer with snacks to university staff and students.

So the best remedy to avoid excessive spilling is to wait for the excess air bubbles to settle before opening the can. The authors suggest (tongue in cheek) that their findings could discourage the practice of tapping the cans, thereby avoiding “tapping-related finger injuries (e.g., damaged tendons, ligaments, RSI)” — apparently a genuine concern, if a 2006 study is any indication.

The strategy of waiting rather than tapping could also benefit those prone to drinking too much beer, encouraging beer lovers to slow down to waste less beer. “Our study suggests that an entire can of beer can be preserved by settling about 100 shaken cans,” the authors wrote. “Post-secondary students, economists and other frugal beer aficionados are likely to find satisfaction in this fact.”

By akfire1

Leave a Reply

Your email address will not be published.