Why Bubbles in Guinness Fall

ts4z writes "Reuters reports: 'Australian scientists say they have answered a question that has plagued and entertained drinkers for generations -- why do the bubbles in a glass of Guinness appear to be falling to the bottom?' I found the full story on Yahoo. Explains my endless facination with the stuff. " Hah! Beer and science working together. It's beautiful.

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Guiness Unified Theory

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Guiness Unified Theory - GUT ---------------------------- At the beginning of the Universe, there was Guiness, and there was a bubble. The bubble, unable to resist the temptation to go up, did so. Once it reached the top, it had to come down, so it did. T+2s: There is Guiness, and there is a bubble, going up and down. The other bubbles, realising that this bubble was breaking the state of equilibrium, decided to join it, in it is endless monotonous cycle. T+3s: There is a Guiness, and there are bubbles. The bubbles are in a state of equilibrium. Is this, the future of the universe ? T+300s: A guy comes along, and sees a Guiness, and he sees bubbles. He is fascinated by the bubbles going up and down. He is so fascinated, he decides to create the rest of the universe, the stars, the planets, the comets, and other celestial objects. T+5Days: The guy is still fascinated by the Guiness, and its bubbles. He finds nothing so interesting in the rest of the universe he has created, so he puts plants and animals, on some planets. T+6Days: There is the Guiness, and there are the bubbles, and there is the rest of the universe. Still, the Guiness, with its bubbles, is more interesting. The guy ponders, while watching the bubbles go up and bubbles go down, and decides to put intelligent being, in the form of himself, on of the planets. He calls that being 'Man'. T+6.5Days: There is a Guiness, and there are bubbles, there is the rest of the universe, and there is Man. The first guy, gets a bit thirsty. He looks at the Guiness, and unable to resist the temtation drinks it. T+7Days: There is no Guiness, and there are no bubbles, but there are stars, planest, moons and, then there is Man. The first guy, the guy who has been there from the beginning of universe, and who is now totally drunk, looks at the man, and, he feels that the man looks too happy, and content. Then, he creates a woman.

Have you ever taken a Guiness can apart?

[Jack William Bell]

I love those little nitrogen widgets they put in them. It is nitrogen that makes the 'small bubbles' required for the creamy head and the downward flow (as the article points out, the bubbles must be less than than 0.05 mm for this).

But the widgets themselves are a truly cool piece of engineering. They hold the nitrogen under pressure until the can is opened and then inject the gas into the beer through a hole so small it almost has to have been drilled by a laser.

The first time I took a Guiness can apart was documented by my girlfriend on her Web Journal. We did some interesting web searchs for more information on the thing. Turns out the widget is patented, and only one of several versions of the same (all of which are patented). Apparently there was a fairly significant research effort by competing companies to re-create the correct creamy foam on canned stout.

I think I speak for all of us when I say "Thanks! It was money well spent!"

Jack

Re:Have you ever taken a Guiness can apart?

[Saurentine]

I love those little nitrogen widgets they put in them. It is nitrogen that makes the 'small bubbles' required for the creamy head and the downward flow (as the article points out, the bubbles must be less than than 0.05 mm for this).

But the widgets themselves are a truly cool piece of engineering. They hold the nitrogen under pressure until the can is opened and then inject the gas into the beer through a hole so small it almost has to have been drilled by a laser.

I don't think that the little widgets actually hold the nitrogen in them throughout the shipping process. Without knowing the manufacturing details, it would make more sense that they put them in there with nitrogen in them, but they're frozen at the time of insertion. The can filling and capping process is done immediately afterward, very quickly. The hole is always there, and it cannot hold the nitrogen in the device during transit.

Then nitrogen then thaws, pressurizing the can to a rather high equilibrium point and Guiness absorbs virtually all the nitrogen during shipping.

When you open it, the pressure at the can's pop-top drops almost instantaneously, while the widget's tiny hole prevents the pressure from dropping as rapidly. The relative imbalance of pressures creates a brief but very energetic internal fountain of Guiness in the bottom of the can! The shearing forces of Guiness rubbing up against itself then releases much of the trapped gasses in the Guiness in dramatic fashion. This is why the foam up best when you crack the top quickly rather than breaking the seal slowly.

I sacrificed a particularly noble can of Guiness to test this theory once by chopping it open with a very large thin-bladed adze and my observation was that the device was literally squirting Guiness and not venting gas.

A very, very costly experiment indeed, but I had to find out what was going on in the magic can!

The Guinness Widget Explained

[mindstrm]

Okay. The 'widget' in the can of guinness.. here goes.

Guinness is brewed iwth a 75/25 mix of N2/CO2 (You know.. Nitrogen gas/Carbon Dioxide). CO2 apparently creates much more pressure when compared to dissolved Nitrogen... anyway...

When the publician pours you a draught guinness, usually the guinness is passed through a filter with a few tiny pinholes in it.. this causes the beer passing through it to release it's nitrogen en masse, and causes that nice creamy head we all know and love.

Now.. many say the 'widget' in guinness contains compressed gas, and releases that gas when the can is opened... but they, having had a few already, forget that beer (like water) doesn't compress really... and could not possibly hold a compressed widget closed... what really happens is this.

The widget is a plastic container with a few very tiny pinholes laser-drilled into it. This is put in the can, the can is filled most of the way up with guinness, and a drop of liquid nitrogen is placed in the can, and then it is immediately sealed. As the liquid nitrogen turns to gas, the gas is absorbed into the beer, and also increases the pressure on the beer (by increasing the gas volume in the available space) causing liquid to be forced into the widget through those little pinholes.... under pressure. Now.. when the can is opened, some of the beer vacates the little widget, and by moving through these pinholes, acts similar to the bartenders filter, and causes more of the 75/25 n2/co2 mix to be released.. giving a nice, creamy head with strange properties.