Scientists explain the physics of a perfect Guinness pour

A new study from scientists at Osaka University and Kirin HD has revealed the unique physics behind a perfectly poured pint of Guinness.

Everyone knows that getting the pour right is one of the main factors that affect the quality of a pint of Guinness. But have you ever wondered why? Well, wonder no more as these scientists explain the physics of a perfect Guinness pour.

The legendary brewery established its unique pouring technique back in 1959, and it been a staple part of the Guinness experience ever since.

An integral part of the experience – a perfectly poured pint of Guinness

The perfect pour is an integral part of the Guinness-drinking experience.
Credit: commons.wikimedia.org

The system developed by brewers at Guinness alters the elemental texture of the resulting pint. And to this day, it is a fundamental part of the Guinness drinking experience.

There is a strict six-step process to create the perfect pint. And now, scientists at Osaka University and Kirin HD have explained the physics of a perfect Guinness pour.

The study, published in Physical Review E, explains the basic principles of physics that contribute to the perfect pint of Guinness.

Cascading flow – all in the bubbles

Scientists explain the physics of a perfect Guinness pour.
Credit: Pixabay / AntonioTerranova

Explaining the physics of a perfect Guinness pour, the researchers clarify why the nitrogen bubbles found in the stout flow similar to a fluid.

They explain, “In a glass of stout beer, a very large number of small dispersed bubbles form a texture motion of a bubble swarm moving downwards.

“However, it is unknown why the bubble cascade is observed only in stout beer with nitrogen, such as Guinness beer.”

They observed that bubbles in most freshly opened carbonated drinks move upwards, following Archimedes’ principle. However, this is where stouts with nitrogen, such as Guinness, differ from the rest.

So what is the physics of a perfect Guinness pour? – so-called collective flow

It is all down to 'collective flow'.
Credit: Pixabay / jarmoluk

In researching the unique structure of the perfectly poured pint, scientists have come up with an answer. They conclude that the ‘collective flow’ behaviour causing bubbles to move downwards results from how the pint is dispensed.

Osaka University researcher and lead and senior author of the study, Tomoaki Watamura, explained the experiments undertaken.

He said, “A wide range of lab work and computational simulations has been useful for estimating individual and collective bubble motion. But only after the flow has occurred.”

He continued, “We’re interested in predicting cascading flow via mathematical modelling, rather than results from experiments or simulations after the fact.”

An in-depth study – various experiments

Scientists explain the physics of a perfect Guinness pour.
Credit: Pixabay / brunamazzer

In an attempt to explain the physics of a perfect Guinness pour, the scientists undertook several numerical simulations. These involved a transparent “pseudo-Guinness fluid”, made up of small hollow particles in tap water and actual Guinness beer.

They investigated the effects of particle concentration, inclination angle, particle diameter, and container size on the cascading film flow.

Shockingly, the study revealed that the unique cascading bubbles found in Guinness might not require nitrogenated stout beer after all.

Kirin HD researcher Hideyuki Wakabayashi explained, “The bubble diameter and bubble volume fraction in carbonated water, poured into the approximate dimensions of a common 200-litre drum with inclination angle, facilitate cascading bubbles.”

Wakabayashi continued, “The associated fluid motion near an inclined container wall pertains to maintenance of product quality during brewing. Thus, suggesting an immediate application of our findings.”

So, there you have it – the science behind a perfectly poured pint of Guinness.

What’s more, it is not only hoped the findings will explain the unique science behind Ireland’s favourite beverage. Rather, they could have a hugely positive impact on several sectors, including pharmaceutical production and city water purification.