We have all had our share of soda cans foam from being shaken around too much, but why does it make such a mess?
According to Life’s Little Mysteries:
Carbonated soda consists of carbon dioxide dissolved in a liquid. Inside a sealed can, interior pressure prevents gas from escaping the liquid (much the same way that altitude and atmospheric pressure affect the boiling point of water). Crack it open and some CO2 gas escapes; pour it out and more gas escapes, foaming into the characteristic, nose-tickling head.
When you shake a can of soda, you add energy to the system, which enables bubbles to form – usually along tiny imperfections on the sides and bottom of the can. Like a beach ball held under water, these bubbles will exit the liquid quickly and violently once pressure is released, shooting out so fast that they carry a stream of liquid along with them.
I have always believed that flicking the bottom of the can a few times helps settle down the pressure inside the can but according to Pepsi and Coke, I’m mistaken.
Both Pepsi and Coke agree that tapping the can does not lower pressure, but instead adds energy to the system thus creating more bubbles. Experiments performed by Snopes.com came to the same conclusion. If anything, it’s the time that you take flicking the can that causes the pressure to lower.
This doesn’t mean that you are entirely powerless. Cooling the can briefly in the fridge or freezer can help speed things up.