Glass And Gushing
The debate of tapping aside, the actual material that the container is made from may also reduce gushing. It has been shown that the amount of foam formed when pouring beer into glasses of different “wettabilities” – the extent to which water wets a material – can affect not only the amount of beer head formed but also the size of the bubbles on the inside of the glass. This information is relevant when such bubbles are thought to be the cause of gushing.
Another important factor when it comes to the level of gushing is the stabilisation of the bubbles caused by the presence of large molecules in the drink. This is why some beers have long-lived foam heads compared to the short-lived bubbles at the surface of, say, sparkling water. But such foam stabilising agents are a conversation for another day.
Diagram drawn specifically for this article
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. This is because pressure waves caused by the impact create tiny “mushroom clouds” inside the bottle that eject huge quantities of liquid as they escape.
So this summer why not try different ways of opening your fizzy drink – and see how much of it you end up wearing.