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The Fascinating Science Behind Beer Foam

Posted by timothy on from the ok-now-explain-my-flickering-lights dept.

RenderSeven writes "Science has so far been at a loss to explain why tapping a beer bottle with another causes it to explosively foam over. Thanks to a grant from the Spanish Ministry of Economy and Competitiveness, a research team at the University of Madrid studying fluid mechanics has found the answer with some fascinating slow-motion video. Their soon-to-be-published paper found that tapping the bottle (or shooting it with a laser) causes a series of compression and expansion waves, that generate unstable buoyant plumes, quickly turning most of the liquid into foam. PhysicsBuzz notes that the process is very rapid and nearly unstoppable once started."

14 of 73 comments (clear)

  1. LOL .... by gstoddart · · Score: 2

    Their soon-to-be-published paper found that tapping the bottle (or shooting it with a laser)

    I don't know about mixing beer and lasers.

    Just saying. ;-)

    Still, maybe we can look forward to beer bottles which are designed to prevent catastrophic foaming in cases like this.

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    Lost at C:>. Found at C.
  2. Beer and lasers. by fahrbot-bot · · Score: 4, Funny

    Their soon-to-be-published paper found that tapping the bottle (or shooting it with a laser) causes a series of compression and expansion waves, that generate unstable buoyant plumes, quickly turning most of the liquid into foam.

    Just one more reason sharks are lousy drinking buddies.

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    It must have been something you assimilated. . . .
  3. Actually there is a ninja defense trick here by GoodNewsJimDotCom · · Score: 2

    It says once the bottle is tapped, you have 1 ms to put your thumb over the mouth of the beer bottle. Of course even gamers know its hard to react sub 33ms, so 1 ms looks bleak... But look at it from another angle: If you see some jerk coming to tap your bottle, there is some reaction time there! So thumbs over the opening folks.

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    God spoke to me
  4. I make beer... by dargaud · · Score: 4, Informative

    ...and foam is a mix of two things: a gas (here CO2) and a liquid that can hold the gas, meaning something a lot more complex than water. Usually it's a mix of proteins, in a way similar to the way gluten holds the bubbles inside the bread to let it rise. I have some bottles that, if opened brutally, will turn entirely to foam. Others will have the wanted 'normal' foam: a few inches which lasts for a long time. Others have lots of gas but no foam. Soda makers in recent years have actually started adding anti foaming additives to their drinks; have you noticed that you can't shake a friend's coke and have it explode in his face anymore ?

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    1. Re:I make beer... by jm007 · · Score: 5, Funny

      Ah... that explains it. I had become somewhat nervous about the beverages handed to me by my grade school son ever since he learned about that prank. Nothing ever happened... and I thought he was just being a good, thoughtful boy.

    2. Re:I make beer... by gstoddart · · Score: 4, Informative

      Ah... that explains it. I had become somewhat nervous about the beverages handed to me by my grade school son ever since he learned about that prank. Nothing ever happened

      I learned a long time ago how to open a can without too much fear of this.

      Tap the top of the can a couple of times, and crack it open just enough to let a small amount of pressure escape, and wait a little while. It might foam a little, but you can actually 'burp' off most of the pressure if you're careful.

      Even back in the 80s I could open a can which had been shaken without much incidence of spraying. And I've always opened cans that way since because, well, my friends weren't good, thoughtful kids when it came to that. ;-)

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      Lost at C:>. Found at C.
    3. Re:I make beer... by cayenne8 · · Score: 2

      Ah... that explains it. I had become somewhat nervous about the beverages handed to me by my grade school son ever since he learned about that prank.

      Well, an easy way to combat that...open every beverage he brings you, pointed back at his face...

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      Light travels faster than sound. This is why some people appear bright until you hear them speak.........
    4. Re:I make beer... by gstoddart · · Score: 2

      4) the main useful thing you did was the slow opening maybe.

      Entirely possible. I haven't done rigorous testing to isolate which aspects of it are the biggest factor. If someone was to give me a grant I might. ;-)

      But I successfully went through my adolescence opening cans that I knew my friends had shaken and never got sprayed in the face.

      So I pretty much have kept opening cans that way since.

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      Lost at C:>. Found at C.
    5. Re:I make beer... by gstoddart · · Score: 5, Funny

      This sounds like it requires further testing. The setup: 5 identical cans, 4 shaken, one left unshaken as a control.

      Oh you'd need much more than that.

      You need to test beer (light beer, normal beer, dark beer, American beer), sodas (clear, dark, diet, rootbeer). You could also test energy drinks.

      You need to control for how cold the can and it's contents are. You could test for can size (is a tall can fizzier than a short can?). You could test the ratio of the can height to diameter. There's likely different types of pop-tops.

      You might also need to determine the threshold for spontaneous can explosion where it's coming out even if you don't do anything. We'll need a paint shaker for this.

      Hell, we might also need to do tests to determine if the likelihood is determined by how inconvenient it would be (critical need detectors and dress clothes).

      I'm going to need a truckload of beers, sodas, a walk in fridge, a normal fridge, a bar fridge, several changes of wardrobe, two assistants, a steady supply of pizza, a lazy boy, a paint shaker, a monkey, 4K of cocaine, some LSD, several hookers, a high speed camera, a good internet connection and a really fast car.

      The only thing I'm worried about is the bats. ;-)

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      Lost at C:>. Found at C.
    6. Re:I make beer... by OglinTatas · · Score: 3, Informative

      You'll see that on plastic soda bottles (pop bottles, depending on your origin) the threads are broken by gaps. This is to allow you to do just that-- crack the top and let the pressure release. You may have to crack/seal it a few times to safely remove the top.
      If the gaps were not there, you would have to unscrew the top much further to vent, and you would risk blowing the cap off and an ensuing fountain of foam.

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      More music, fewer hits
    7. Re:I make beer... by dwywit · · Score: 2

      Nuh - it's fat/oil. Collapses beer foam very quickly. Try this (and it's only in the interest of science that I recommend wasting a beer this way). Wipe a smear of cooking oil around the inside of a clean empty glass. Do it as far down the glass as you can get your finger, then tilt the glass and pour cold beer down the side of the glass to make sure the beer comes into contact with the oil. Put the glass down then pour cold beer the same way into another clean glass. Observe which one keeps the head longer.

      There are some valid reasons to add certain salts/minerals to beer when brewing - some water supplies lack trace elements or salts needed by the yeast. I wouldn't recommend dumping plain ol' NaCl in there, though - it's a yeast growth inhibitor.

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      They sentenced me to twenty years of boredom
  5. Practical application by Plazmid · · Score: 2

    Perhaps this could be used to figure out exactly how deadly limnic eruptions are triggered.

  6. That's funny... by Shoten · · Score: 2

    ...I always thought that the explanation for the phenomenon was, "The guy you're drinking with is a fucking douchebag."

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  7. Ah yes... by Doghouse13 · · Score: 2

    ...the old, hoary "science has been at a loss to explain.." hyperbole. Really? In reality, I suspect any number of science students could have made a pretty good guess on that one.