It’s a worldwide and age old idea that tapping a shaken up can of beer will stop it from fizzing over when opened.
But now that action has been debunked as a myth, thanks to a study from a Danish university called ‘To beer or not to beer: does tapping beer cans prevent beer loss? A randomised controlled trial.’
Twelve researchers tested the theory, aiming to evaluate the effect of tapping a can of beer, as “preventing or minimising beer loss when opening a can of beer is socially and economically desirable.”
According to global science and technology publication NewScientist, the theory behind tapping a shaken beer is in fact rational. When beer is shaken, carbon dioxide bubbles from on the inner wall of the can, swelling and rising to the surface when the can is opened and depressurised, taking beer with them.
NewScientist say that tapping the can is supposed to “dislodge bubbles of carbon dioxide from the sides of the can, making them rise to the top where they won’t expel beer when the can is opened.”
Using 1031 units of 330ml cans, donated to the study by Carlsberg Breweries, the researchers conducted a trial, randomly separating the cans into four groups: unshaken/untapped, unshaken/tapped, shaken/untapped, shaken/tapped.
The method used in the research was to shake two groups of cans for two minutes. Two groups were also tapped on the side of the can three times with a single finger. All cans were then weighed and opened, with any spilt beer mopped up before all cans were reweighed.
Results of the paper stated: “For shaken cans, there was no statistically significant difference in the mass of beer lost when tapping compared to not tapping (mean difference of -0.159g beer lost with tapping).”
Of course, in the daily workings of this industry, we’re unlikely to encounter beer cans that have been shaken consistently for two minutes. But the message remains the same – tapping a shaken can doesn’t completely protect from spilling precious beer.
The study has said the only way to avoid losing liquid is to wait for the carbon dioxide bubbles to settle before opening the can. And in further perfect news for this busy festive season, it says there’s no proven way to know when these bubbles have settled, as it all depends on how shaken the drink was as well as characteristics of the can and the beer recipe.
So if you drop an unopened beer over summer, good luck.