How does tapping a soda can make the fizz go down?

Question

Or is that just an "old wives tale"?

Answer 1

well I just stick my finger in it and the fizz goes down real fast! So, I wonder what makes that happen?

but tapping it...... i think that is a bull c**p fairy tale lol

Answer 2

Respectfully, it is supposed to do something, but whether it does depends on a bunch of different things so sometimes it doesn't appear to do anything.  To understand why there is a purpose but sometimes it is completely useless you have to understand why soda "fizzes" to begin with.  

When a soda bubbles over when opened, what is happening is when you open the can or bottle, the internal pressure decreases from around 30 psi to 0. When that happens, bubbles that are already present in the soda rapidly expand and if there are enough of them, and there is soda between them and the opening of the can/bottle, they shoot soda out the opening.  

What tapping the can is supposed to do is dislodge bubbles clinging to the sides of the can and bring them to the surface.  If the bubbles are at or near the surface, then when they expand they don't shoot soda out the top since there isn't any soda between them and the opening.  Typically, bubbles form on the can/bottle walls when the soda has sat for a while and warmed up a bit, like you took it from the refrigerator and left it on the counter for a while.  

However, if the bubbles are suspended in the soda, rather than clinging to the walls, then tapping doesn't do anything since the bubbles don't get dislodged.  Then, when you open the soda it will fizz over as if you hadn't ever tapped it.  Typically this is the case when a soda has been shaken or bumped, the bubbles are already suspended in solution and tapping doesn't do any good.  Since this is the more common occurrence with a soda, most people equate tapping with being useless.  It's not though, it's just useless in that situation.  (There can also be instances where the bubbles on the can walls are too small to be dislodged easily by tapping the can.)

So tapping a can often doesn't do any good, probably more often than not, but it isn't correct to say it is never effective.  

Answer 3

ah.  thank you for asking this question so other people will now understand.

The answer is simple.  It dosent do anything!  I have no idea who dreamed this up and I have no idea who passed this weird "tradition" on.