Why would the cap shoot off a 2-liter bottle of Coke, but no soda came out?

Question

Last night, my fiance tried to open a 2-liter bottle of Coca-Cola and found it very difficult. The soda was delivered by a pizza delivery person, so I am assuming it was jostled in the car on the way over.

Using considerable strength, my fiance was able to turn the cap to the bottle after several tries. Once loosened, the cap shot off the bottle and into my fiance's eye, causing what we hope is temporary blindness. His eyelid is swollen almost shut and he cannot see out of his eye when opened. We had to go to the ER and the Dr. diagnosed him with a hyphema (blood in a chamber of the eye). This is a very serious injury and he is on bed rest until the bleeding stops. After the bleeding stops, the question of his eyesight and possible surgery will be addressed.

The strangest part about this entire thing is that the Coca-Cola in the bottle did not rise up at all when opened. Nothing came out of the bottle at all. Why would this happen? If you shake a Coke and then open it, Coke will come out of the top, or at least rise up a little. Why not this time, especially given the force of which the cap came off. Could this bottle have been tampered with?

Thanks!

Answer 1

Best of luck to your fiance. I hope he holds in I really do.

Sometimes a lot of tapping can just settle down the carbonation.

or when opening, the bottle could of been pressed down causing lots of pressure.

However, its not really the bottles fault.

Answer 2

wow i can't believe this. hope your fiance gets better.

Answer 3

What kind of cap is it?  When I was looking into your other question (in Law & Ethics), I came across a Saskatchewan case with a somewhat similar fact pattern (and very similar injuries).  In that case, it was an aluminum cap which had been improperly closed in the first place.  So it took some doing for the person opening it to get it loose in the first place, but once it was loose, there was no threading for the cap to latch onto.

The court quoted the brochure of the closure system, warning of possible consequences of improperly applied closures:

"Sometimes, ordinary pressure in a package can suddenly eject an improperly applied closure with considerable force. This can result in serious injury, often to an eye."

So I guess the physics of it are fairly straightforward.  Even in an unshaken bottle, the air inside the bottle is pressurized, and so if there's a problem with the sealing of the cap, it basically turns the bottle into a projectile weapon.  Still difficult to understand how your fiance's hand wasn't between the cap and his eye.  (In the Saskatchewan case, the girl had grabbed a nutcracker to try to loosen it.)

Answer 4

It wasn't shaken hard enough.