Does Tapping the Top of a Soda Can Really Do Anything?
Most of us have a friend or have at least seen someone perform this odd ritual: tapping the top of a soda or beer can before cracking it open. They’ll tell you that it prevents the can’s carbonated contents from foaming over, but does it really?
In a word, no.
Just like how a four-leaf clover is supposed to bring you good luck or how breaking a mirror or walking under a latter will bring you the opposite, this too is a mere superstition.
Why Tapping Doesn’t Work
Carbonated soda consists of carbon dioxide dissolved in liquid, causing the can to be pressurized. The interior pressure prevents the gas from leaving the liquid. But once you open the can, the CO2 gas begins to escape.
Now, by shaking an unopened can of soda, you add energy to the system, enabling the gas to unbind from the liquid and form bubbles. If you open the can while it’s in this excited state, the gas will shoot out of the can, carrying a stream of liquid with it.
Those who ritually perform the tapping method believe that it breaks up the bubbles. However, both Coke and Pepsi agree that the practice does not work. In fact, you’re probably generating more bubbles by adding energy to the system.
Snopes.com conducted their own experiments and concluded that the claim is false. In fact, the only thing that the tapping method achieves is giving the liquid time to reabsorb the CO2 inside the can.
How to Actually Prevent a Soda from Foaming Over
Just as time heals all wounds, so does it stop bubbles from shooting out of a shaken soda can. Chilling a can of soda in the fridge or freezer will also help to prevent foaming. This is because the colder temperature causes the CO2 molecules inside the can to move more slowly, making it easier for the liquid to reabsorb them. Just don’t leave the can in the freezer for too long, or else you’ll have a different sort of mess to clean up.