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from the whether-tis-nobler-to-tap-or-not-to-tap dept.
Tech Review reports on some Danish experiments on beer foaming, https://www.technologyreview.com/s/614907/does-tapping-the-bottom-of-a-beer-can-really-stop-it-fizzing-over/ (likely also available on archive.is if you don't subscribe).
Among the great questions in science, one stands sadly neglected: Is it possible to stop a shaken beer can from foaming by tapping it before opening?
There are good theoretical reasons to think this should work. The tapping should release any bubbles that are stuck to the inside walls of the can. These should then float to the surface and dissipate, making the beer less likely to foam when it is opened. But is this true?
Today, we get an answer thanks to the selfless work of Elizaveta Sopina at the University of Southern Denmark and a few colleagues. This group has tested the theory for the first time using randomized controlled trials involving 1,000 cans of lager. And luckily for the research team, the result raises at least as many questions as it answers, ensuring a strong future for beer-related research.
[...] The cans were then shaken using a "Unimax 2010 shaker" for two minutes at 440 rpm. "Pilot testing revealed that this shaking method successfully mimicked carrying beer on a bicycle for 10 minutes—a common way of transporting beer in Denmark," says Sopina and co. Unwanted foaming must be at epidemic levels there.
The researchers then weighed each can, tapped it by flicking it three times on its side with a finger, and then opened it. Finally, they weighed the can again to determine the amount of beer that had been lost.
The results are palate tickling. Sopina and co compared the amount of beer lost for tapped and untapped cans that had been shaken and found no statistical difference—both lost about 3.5 grams of liquid to foaming.
They also found no meaningful difference between the cans that had not been shaken—when opened, they lost about 0.5 grams on average.
Personally, I don't have a dog in this fight, always drink bottled (or tap) beer. But for you can users I suggest that looking inside the can might be a more direct way to see what is going on with the bubbles--seal up a can with camera & light source inside, or make some cans with a small viewing window. But that might generate an answer, where the goal of this research seems to be to consume more beer...For Science!
(Score: 2) by looorg on Thursday December 12 2019, @01:50PM (10 children)
Should be the same issue for soda etc. I dont tap it. Just slowly rotate the can one or two times (top-bottom axis). That always worked in my experience.
(Score: 3, Informative) by The Mighty Buzzard on Thursday December 12 2019, @01:58PM (3 children)
Dunno why that should work either. It's not so much that there are bubbles in the liquid, it's that quite a bit of CO2 has come out of solution. There's really not a whole lot you can do to remedy that except keep the container cold and wait.
My rights don't end where your fear begins.
(Score: 3, Interesting) by FatPhil on Thursday December 12 2019, @02:51PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Interesting) by looorg on Thursday December 12 2019, @03:37PM (1 child)
I'm not saying that it makes scientific sense in any way shape or form, at least not in a way I can explain. I didn't even come up with the idea to begin with but was told, I tested it and it seemed to work. That said I think the idea is that there is an air-pocket at the top of the can. So if you shake it the bubbling will start. This could be checked by just taking a can, feel it. Then shake the can, feel it again and you should notice that the pressure inside the can is higher. So I would think the idea of rotating the can top-to-bottom-to-top again would be that the air-pocket will change direction as it travels to the bottom then to the top again and perhaps it's just that enough time have passed for it to "calm down" again. At least after doing it I have never had a big soda fountain spew forth as I open the can.
(Score: 1, Interesting) by Anonymous Coward on Thursday December 12 2019, @04:19PM
> Then shake the can, feel it again and you should notice that the pressure inside the can is higher.
Did this experiment in the instrumentation lab I took in the mechanical engineering department. We started with normal Coke cans, polished a bit of the surface and bonded/glued on strain gages* to measure any changes in the strain (stretching/contracting) of the aluminum. The gage becomes one arm (or more, depending on the gage types) of a Wheatstone bridge and tiny changes in strain can be measured. This is a common tool in all kinds of structural testing.
At this point in the experiment, shaking the can had no effect on the gage readout--thus no change in pressure. Made sense to me, since shaking the can does not add or remove any material from the can (or change the volume of the can), but some of my lab partners were expecting a change in pressure.
Then we opened the can to release the pressure (I think we tapped or waited long enough to not make a geyser). The strain gage setup showed material contraction. While I don't recall measuring temperature, a really precise experiment might do this as well--since releasing pressure typically cools things down.
The final step was to cut open the can, measure the thickness of the aluminum at the gage location and calculate the hoop stress reduction from the change in strain--which could then be used to calculate the initial pressure. IIRC, we got about 80 psi (550000 Pa) for our can, but it has been a long time and my memory could be off.
* Yes, "gage" is the spelling that I learned. Here is a link to one of the oldest manufacturers who traditionally use this spelling https://www.micro-measurements.com/stress-analysis-strain-gages [micro-measurements.com]
(Score: 3, Funny) by DannyB on Thursday December 12 2019, @02:26PM (5 children)
For soda I avoid all foaming over by simply asking the waitress for a large picture of diet coke.
The lower I set my standards the more accomplishments I have.
(Score: 0) by Anonymous Coward on Thursday December 12 2019, @02:36PM
Does the picture of diet soda have less foaming than pictures of regular soda?
(Score: 5, Touché) by FatPhil on Thursday December 12 2019, @02:58PM (1 child)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by DannyB on Thursday December 12 2019, @03:53PM
And the picture doesn't need to be rotated end over end. Which would not be good.
The lower I set my standards the more accomplishments I have.
(Score: 2) by captain normal on Thursday December 12 2019, @05:30PM (1 child)
I don't care for diet coke (nor any soda drink, other than seltzer water), but I do like my beer served in a pitcher. I would imagine it would not be possible to drink an image of a diet coke.
Everyone is entitled to his own opinion, but not to his own facts"- --Daniel Patrick Moynihan--
(Score: 2) by DannyB on Thursday December 12 2019, @08:52PM
Diet coke is probably acidic enough to dissolve any picture into solution. Unless it has a metal frame.
The lower I set my standards the more accomplishments I have.