Why does tapping a can stop it from fizzing

As soon as a shaken can is opened, it flies to the top and thus overflows the can. Tapping the can has no effect on carbon dioxide bubbles, and will not decrease their ability to overflow once the can is opened. People thought that tapping caused the bubbles to break apart, but that is scientifically impossible.

Tapping may reduce the amount of overflow slightly, but it will in no way stop it from happening. The only way to fix this problem is to wait. Time is the only proven way for dioxide bubbles to start the breakdown process, so the longer you wait to open the can, the less likely it is to overflow. So what part could tapping the top of the can play in this process?

Whether or not this technique actually works is the subject of some debate but there is a theory explaining why it may work. As described earlier, the bubbles in an unopened can nucleate at the walls Figure 2a so tapping the can before opening could dislodge some of the bubbles, enabling them to float to the top of the liquid.

When a can is opened, the bubbles expand Figure 2b with those deeper within the liquid travelling further than those near the surface, displacing more of the drink and possibly resulting in greater amounts of ejected liquid. Bubbles also can be dislodged from the side of the can with violent shaking, of course — but this method introduces more turbulence which increases the energy of the system, resulting in more bubbles in the drink and more spraying when opened.

Sharply tapping the top of an open beer bottle with another has a similar effect, commonly resulting in a colossal gush of beer foam. The debate of tapping aside, the actual material that the container is made from may also reduce gushing. It provided more than a thousand millilitre cans, but had no involvement in the study design or analysis. Half of the cans were put on a mechanical shaker for two minutes, with a level of vigour intended to simulate being transported on a bicycle.

Read more: Beer before wine or wine before beer: the hangover is the same. The cans were weighed before and after opening to measure how much beer escaped. The shaken cans lost on average 3. That may be because beer contains barley proteins that stabilise bubbles, a process that helps to create the foam head in a glass of beer.