While holding a bottle of cream soda today (mighty tasty soda, I might add) I realized that I was subconsciously cradling its neck to avoid having it ‘tapped’, something that has occurred to many partygoers I’ve known, as well as myself.
To those of you who don’t know what ‘tapping’ is, it’s the practice of hitting the very top of a bottle containing carbonated liquid with a hard object (almost always it is done with the bottom of the bottle in the tapper’s hand, as this is the most subtle approach). If the tapper is good at it, neither of the bottles will break. The unwary tappee does not know how to respond, of course, since nothing happens immediately. In a very few seconds, though, the substance inside the bottle begins to foam rather violently, overflowing the bottle and making a mess for which the victim, and never the instigator, is blamed.
Now, my experience with this, and conversations while observing this activity seem to imply that it’s the shock wave going through the bottle and resonating at the bottom of the tapped bottle, then propagating into the liquid, or something pseudoscientific like that. Some argue that the coldness of the liquid is a help. But observing myself holding my cream soda, I began to wonder if anyone could provide a good explanation of just what goes on there. I’d buy a case or two of Henry’s to experiment, but I don’t know if I want to devote that much for the sake of science (yet).
panama jack
To Anacreon in heaven, where a sat in full glee,
a few Sons of Harmony sent a petition.
I dunno, Jack, all the parties I ever went to, they wouldn’t let us have glass, only plastic.
Party lore at the dorm I lived in said that it was the air being forced into the bottle that made it foam, like blowing into a drink with a straw on a larger scale. It sounded reasonable at the time, but then again we were generally pretty buzzed by the time we got around to talking about it.
My theory, when I first saw this, was that when the two bottles contact, the liquid in the top bottle is subjected to increased pressure, while the liquid in the bottom bottle is subjected to decreased pressure from the bottle bottom pulling away from the beer. Pressure is what keeps carbonation in the liquid, so a lot of microscopic bubbles form with the decrease in pressure.
Essentially, this is the same mechanism that causes pop to make bubbles when you first crack the seal on a bottle. For the beer bottle on the bottom, the pressure decrease is only temporary, but the damage has been done, and it foams up.
So after demonstrating this to my friend and physics teacher tonight, he told me that my theory about the air was way off base. Mind passing me some salt for these here Nikes?
He seems to favor panamajack’s idea about the shock wave. Something about nucleating the CO2 molecules, and once you start the reaction it keeps going … I’m not a physicist and there’s probably someone out there who could explain it better than I could. At any rate, just ignore what I said before, if you weren’t already. <g>
Nucleating the CO2 molecules sounds cool; I think I’ll just use that as the explanation. And I bet it’d blow away anyone who’s had a few to drink. (that seems to the problem with this, it’s rarely discussed by sober people).
ZenBeam, I think I partly like the explanation but I’m not sold on it. It seems that it might have something to do with it, but the reaction does seem more chain-reaction type like JayLa pointed out; I think to be all due to pressure would require a greater difference.
My guess is that we’re describing the same effect slightly differently.
panama jack
tonight this fool’s halfway to heaven and a mile out of hell, and I feel like I’m coming home.