Stirring beer runs the foam backwards

By Nathalie Baylaucq 9.12.2019

Have you ever stirred your beer on a glass? Did you notice what happens? Are you familiar with this phenomenon? We explain you everything!

By swirling beer in a glass, one can witness a rather peculiar phenomenon: that of the foam that turns in the opposite direction given to the glass.

This observation has, of course, captured the attention of several scientists including Frédéric Moisy and Wietze Herreman. The first is a professor at the University Paris-Sud, and the second is a theorician. Assisted by a student intern, Julien Bouvard, they helped to give an explanation to this event.

It follows from their experiments that in the presence of a rather large density in the glass, it engages a counter-rotation which is at the origin of the situation of the foam upside down. Point out that it is also possible to note this fact on the surface of a tea, or an espresso. In addition, to access their entire presentation, please consult the June 25 edition of Europhysics Letters.

Don’t drink and drive. Enjoy responsibly.