Does it really help to tap the can with your finger?
We'll probably just knock on top of the tin out of sheer habit, because we've heard at some point that it does not splash. But is that true?
The answer is no: in most cases it does not help to knock on top of the can. To understand why, let's first explain how it comes to overblowing.
If the can is quiet, it is filled to a good extent with our drink, in the upper part of the can, however, gas has settled. Now, when the can is shaken (or tumbled down through the soda machine), this gas enters the drink in small bubbles - and these bubbles settle on the inside walls of the can.
If we now open the can, the gas escapes upwards - and all the bubbles that have settled on the inner walls, "tear" the liquid with outside: our can foams over.
The aim of the knock would therefore be that the bubbles that have settled on the inside of the can, solve and rise to the surface again. This does not work most of the time, though, by knocking on the top of the lid!
It works better, if you knock with your fingertips gently on the side of the can - once around the can. This ensures that the bubbles inside easier ascend and when you open it's finally no mess!
