If you haven’t done it yourself, you’re at least likely to have observed others give a light tap to a beer can. Supposedly, tapping the beer can is way to keep it from fizzing over when you open it. But does it actually work? Sadly not, according to the researchers who just carried out a random trial to find out.

A team of scientists, led by Elizaveta Sopina, studied whether or not tapping a beer prior to opening reduces the amount of overflowing foam.

Bubbles of carbon dioxide form on the inner surface of the can and when opened, the depressurization causes the bubbles to swell and rise to the surface — often taking precious beer with them.

And so in theory, proponents of the practice say that tapping dislodges bubbles from the sides of the can. This causes them to rise to the top and therefore won’t expel beer when the can is opened.

“Being a scientist, I always wanted to know whether it actually has an effect,” says Elizaveta Sopina at the University of Southern Denmark in Odense.

Sopina, who is doing a post-doctorate in health economics, gathered an intrepid group of scientists from the university’s PhD association to help her conduct the experiment in her spare time.

She and her colleagues approached the Carlsberg Brewery to supply beer for the experiment. The brewery provided more than a thousand 330 ml cans but had no involvement in the study design or analysis.

Half of the cans were set to the side. The other half of the cans were put on a mechanical shaker for two minutes at a level intended to simulate being transported on a bike.

Half of the can from the shaken and unshaken groups were then “tapped” by flicking by flicking them on the side three times.

The testers who opened the cans were unaware as to whether their cans had been shaken, tapped, or simply left alone.

The cans were weighed before and after opening to measure just how much beer escaped.

On average, the shaken cans lost 3.45 grams of beer when opened. The unshaken cans lost only 0.51 grams. Further, tapping the can didn’t make a significant difference to how much beer was lost.

“I was surprised, but not disappointed… it’s good to be evidence-based in your behavior.”

According to Sopina, the evidence suggests that tapping or flicking the beer cans doesn’t actually help the bubbles to rise to the top. It might be because the beer contains barely proteins that stabilize the bubbles and contribute to the foamy head in a glass of beer. Those same proteins may stop the bubbles from rising to the can.

And therefore it’s possible tapping may be useful for other carbonated beverages. Perhaps another test will be conducted in the future.

It turns out the best strategy to avoid any loss of beer, says Sopina, is to simply wait. “If you want to save your beer, let it settle.”

For those who may have been concerned, thankfully, the beer that remained in the tested cans didn’t go to waste. It was offered to the university staff and its students, along with snacks.

Source: https://arxiv.org/abs/1912.01999