I did some Googling around and searched here and the answer given to this effect is generally that the beer is supercooled and opening relieves the pressure allowing the beer to instantly (or near instantly) freeze.
Ok, I get that except a friend was just describing seeing this and swears he did not open the bottle. Further if you look at the video the beer is still capped and they induce freezing by clinking the bottle on a hard surface.
So what is making this happen here? If anyting one would think clinking the bottle would have the effect of increasing pressure as you agitate the liquid (like shaking up a soda to make it explode on someone when they open it).
Just a mildly educated guess, but I would assume the freezing occurs as a result of CO[sub]2[/sub] coming out of solution, thus raising the freezing point slightly.
There’s also an effect whereby freezing won’t occur without nucleation sites for the crystals to form around. Clinking the bottle induces a shockwave in the liquid, causing enough disturbance for ice crystals to form.
If either guess is correct, I take full credit for knowing my ass from a hole in the ground.
Supercooling, I’d say - nucleation sites are one way that ice can start to form in a supercooled liquid, another way is pressure disturbances - in much the same way as those little handwarmers that are filled with a supersaturated solution of sodium acetate can be induced to start crystallising by clicking a little metal spring inside the bag - it creates a small zone of pressure where supersaturation can’t be sustained, crystallisation commences and those crystals provide nucleation for the rest.
I have no clue why or how it happens, but I know from experience it’s not just beer. We once left a pricey (~$50) bottle of champagne in the freezer for a little too long. When we took it out, it was still liquid, so we figured it was OK to open. Upon opening, about 3/4 of it blew out, and the remaining quarter froze solid. We were very sad that day. :mad:
We frequented a bar whose claim to fame was that the temperature of their beer fridge was just so that when the opened the bottle, it would start to freeze, just like in the video. While this was happening, they topped the bottle with gin, which made it thaw, just as quickly. Good times.
I’d agree. A supercooled liquid (i.e., one that it cooled below freezing, but still remains liquid) will freeze if disturbed. Most likely, tapping the bottle released a few carbon dioxide bubble which were good nucleation sites. Once the beer began to freeze, the beer-ice provided the site.
I suspect that if you opened the bottle, it would also freeze immediately.
Once left a six pack of canned beer in the back of a pick up truck in -40 weather. Forgot about it and then remembered and retrieved it. We saw the instant freezing/frozen foam upon opening , but here is the ODD thing… It happened in only 4 of the cans.
Any guesses as to why the 2 cans didn’t display the same behavoir (BTW, they were all opened more or less simultaniously, say with in 15 seconds… they did not have time to warm up signifigantly.)
It could be the bubbles or it could just be the shock - a non-carbonated supercooled liquid can still be made to do this when tapped, because a small area experiences a rise in pressure that means the supercooled state can no longer be supported.
BTW, I think it’s great that there’s video of the phenomenon. I’m pretty sure that without it, there would be some that would have argued that beer isn’t pure enough to be supercooled, so it must have been already frozen through, you just didn’t notice and you only thought you saw it freezing up.
Bolding mine. A shockwave means that the pressure wave is traveling faster than the bulk speed of sound in the medium. It’s just a simple pressure wave, there’s no supersonic activity going on in the bottle. [/nitpick]
