For many of us, it’s almost a reflex action – before you open your lovely, refreshing can of coke , you give it a tap on the top. Do you tap? Or is it just nonsense?
Why? Well, you think it helps prevent it becoming overly effervescent. No one wants to be coated in a sugary soft drink on a hot summer’s day (wasps!).
But is the tapping to stop it fizzing theory more of an urban legend than something grounded in scientific theory?
If you tap religiously then rejoice – there is a good reason as to why this method works, and it is backed up by science.
The science of tapping
Lending his voice to the debate in The Conversation was Christopher Arthur Edward Hamlett, a Chemistry lecturer from Nottingham Trent University.
This is what happens before, during and after a can of soft drink is opened.
“Before the can is opened, microscopic gas bubbles attach to the inside of it (nucleation).”
“When the can is opened, these bubbles increase in size, due to the decrease in the solubility of CO2.
“When these bubbles reach a certain size they detach from the inside of the can and rise up to the top of the can due to buoyancy and displace liquid in their path.”
3. And after?
Christopher does admit there is still some debate over the efficacy of the technique, but the theory of what happens after tapping is explained as follows.
“As described earlier, the bubbles in an unopened can nucleate at the walls 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 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.
“A ‘tapped’ can will have fewer of these ‘deep’ bubbles and so less liquid will be dislodged – and possibly sprayed out – than an ‘untapped’ can.”
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