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Nagging Question
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Does Tapping a Soda Can Stop the Foaming?Warning: contents under pressure |
If you tap the top of a soda can, will it really keep it from foaming when you open it?
Those who think so follow this logic: When you shake a soda can, little molecules of carbon dioxide bump into each other and form bubbles. These bubbles hang around on the sides and bottom of the can until you pop the top, at which time they shoot out, eager to escape to the lower air pressure outside the can. Some liquid clings to them on their way out—and winds up all over your shirt. Tapping the can prior to opening it, the theory goes, dislodges bubbles from the bottom and sides. The bubbles join the big pocket of gas at the top, which escapes harmlessly because it’s above the liquid.
But the theory is wrong. Doesn’t work. “We are not aware of any impact that tapping on the top of a can before you open it has on fizzing over,” said Scott Williamson, a Coca-Cola spokesman in Atlanta. A counterpart at Pepsi concurred, though neither was quite able to explain why the tapping doesn’t work.
It even turns out it could do more harm than good. “If you were tapping rigorously enough to dislodge bubbles from the bottom and the side, you risk creating more bubbles,” said Karl J. Siebert, a biochemistry professor and foam expert in Cornell University’s Food Science & Technology Department.
So tap at your own risk.
I can't believe anybody anywhere in the world was ever stupid enough to believe this.
I see people doing this all the time, even my own wife. I used to get on her for it, now I just figure might as let this old wives tale roll on anyway.....
The thing to do is let it sit undisturbed for about 20 or 30 seconds, and then open it quickly in one smooth motion. Works every single time.
A mallet works for me.
Well, it's always worked for me, so I'll probably continue to do it. I've even watched people shake a can, set it down smartly, tap the top once or twice and open the can- no spray. I take vitamins, too- cheap insurance.
If I suspect a can or bottle of pop of being seriously under pressure, I just open it really slowly. It takes patience and control, but it works ;) Only things this doesn't work on are those non-carbonated drinks like the triple espresso drinks from Trader Joe's. Those always explode on me!!
Well, guys, let me tell you that this information was given to me by my high school chemistry teacher, Jules Dante, first person to ever get a perfect SAT score, holder of many patents, including the Dante method for converting Celsius to Fahrenheit. I didn't believe him because he was a genius. I believed him because he demonstrated it. It works. QED
I'm with foehngoes - I've done this as a party trick before. Either it works, or shaking a can of soda vigorously for 60 seconds has no effect. I have to blame Mr. Lane for consulting a spokesman and a biochemistry professor when he could have easily done a $2, 5 minute experiment to test this theory.
I tend to think this is along the same lines as Grannies Cold Cure Poltice.
The fact that most people believe that it works is because it does - in that you tap lightly on the can for 30-60 seconds and by then everything has calmed down. The tapping doesn't do it. The waiting does. I'd stick with the tapping. I like rituals.
I did some more research and it looks like a British show called "How" used a clear can to demonstrate how this works (and it DOES work!) even though our American show "Mythbusters" has apparently dropped the ball on this one... their experiment failed, but I can't say why because I haven't seen it. I feel certain that location, number, and force of tapping are experimental parameters worth examining.
I've always rolled the can back and forth..seems to settle down a bit.
a co-worker and i tried this after reading today. He bought a coke at the co. vending machine and shook it all the way back to my desk. He set it down and I gave it five brisk taps (wasn't on my desk longer then ten seconds before opening), it foamed, but not above the rim of the can. Very mild for the shaking it got! Try it outside where there is nothing to ruin, if you doubt.
If one doesn't open one's mouth, when one doesn't know what one is talking about, one doesn't look like a fool.
I was just at 7 Habits seminar on Monday... and the instructor used this trick to make one of the points. After vigorously shaking a coke can several times.... he then tapped it a bit and when he opened it, foaming really was minimal.
Tapping the can adds heat to the system, forcing carbon dioxide out of solution. The fifteen seconds you spend lightly tapping it; however, allows the system to equilibrate.
It works. I don't why it does, but it does.
That being said, "my" technique is a little different from the one described here and in the comments. I tap the side of the pop can (near the top) twice (a second time just because I'm weird) and open the can right away. There's no waiting around for 15-60 seconds or continuously tapping.
i think we all have way too much time on our hands...
i think we all have way too much time on our hands...and here i am, too! now, where is my can of coke zero?!
Has anyone tried shaking the can and then opening it WITHOUT tapping it? I believe you'll get the same result-not much foaming. Try it! It works...
Ok, the spokespeople at Coke and Pepsi, and some biochemistry professor explain why tapping shouldn't work. Guess what? Somebody showed me the tapping trick over 20 years ago at summer camp and it has worked every time I used it. I agree with ynniv; stop wasting time asking people about it and try it yourself.
Non Soda geeks ignore this please. Lets look at the soda can from a Pressure-Volume point of view. You know the can is pressurised. Anyone who has opened a polycarbonate plastic (transparent) soda will agree with this & also that there are no bubbles till you open the bottle. The pressure in the unopened can or bottle prevents the dissolved Co2(?) gas from escaping as bubbles till the pressure is released. This phenomenon is called dissolved gas. When you open the can, that pessure holding the liquid & gas is released & the gas starts expanding & thus begins bubbling out of the liquid, thus the situation of tapping an unopened can does not alter the pressure of the can & hence one cannot possibly affect the bubbles till that point of time when the can is actually opened & then only can the bubbles come in to play & then onwards tapping may certainly help dislodge those bubbles which are sticking to the sides & bottom, thus actually assist the process of foaming because in fact, those bubbles are the cause of foam generation. Foam = liquid spheres trapping gas pockets. Hope this helps. My explanation comes from Undergroung Oil exploration, where the oil in the depths of the earth is under exactly the same (but more intense pressure) situation.
Non Soda geeks ignore this please. Lets look at the soda can from a Pressure-Volume point of view. You know the can is pressurised. Anyone who has opened a polycarbonate plastic (transparent) soda will agree with this & also that there are no bubbles till you open the bottle. The pressure in the unopened can or bottle prevents the dissolved Co2(?) gas from escaping as bubbles till the pressure is released. This phenomenon is called dissolved gas. When you open the can, that pessure holding the liquid & gas is released & the gas starts expanding & thus begins bubbling out of the liquid, thus the situation of tapping an unopened can does not alter the pressure of the can & hence one cannot possibly affect the bubbles till that point of time when the can is actually opened & then only can the bubbles come in to play & then onwards tapping may certainly help dislodge those bubbles which are sticking to the sides & bottom, thus actually assist the process of foaming because in fact, those bubbles are the cause of foam generation. Foam = liquid spheres trapping gas pockets. Hope this helps. My explanation comes from Underground Oil exploration, where the oil in the depths of the earth is under exactly the same (but more intense pressure) situation.
FWIW -- this was never a *theory* in the scientifc sense. A theory has been rigously tested time and time again, under highly controlled circumstances, to the point where it can longer reasonably be considered false. It's the highest level of science based epistomology.Of course even theories can be disproven, but it's a pretty high bar.
Now to go shake & tap...
If I recall correctly, soda cans w/the stay on top that we see nowadays were invented so that there would be less foaming. When we use to have the pull tabs, we had more cans that would foam and shoot out soda. I may be incorrect, but I thought that is why they changed it to the tops we have now.
I know that tapping doesn't change anything, but I still do it. It's allways polite to knock before entering.
What hasn't been done is the "double blind" comparison, like they do with experimental drugs. Different people using identically agitated cans, some tapped and some not, and opening both with identical technique. Anything less is less than scientific.
I believe that Rustkam is correct. When CO2 is dissolved in water and kept under pressure, there are no bubbles to dislodge from the sides. Shaking or agitating a can or bottle of soda will, however, change the equilibrium in the can as the small amount of air/CO2 that is undissolved in the container is churned up inside the liquid. It starts to form small bubbles at that point and pulls the dissolved CO2 out of the liquid. That's more or less why shaking the can will cause it to explode when you crack it open.
Now, tapping a can will allow time for the gas and liquid to move back toward equilibrium under pressure. That's generally why tapping on a can seems to reduce the incidence of explosive failures.