Science Questions

How can beer freeze immediately?

Sometimes when I put my beer (330mL glass bottle) in the deep freeze to rapidly chill it, I can take it out and it's still liquid. If I then leave it for a few minutes on the side and come back to drink it, it goes all icy. Why is this? Surely once I've taken it out of the fridge it should instantly start getting warmer, not turning to ice! Steve from New Zealand

I reckon it's down to something similar to our kitchen science that we did this evening. That was all about nucleation. What you need is one tiny crystal to kick start the process. But where does this first crystal come from? Well, say he puts the glass bottle of this stuff in the freezer, and the glass where it's not in contact with the liquid, gets that little tiny bit colder because the liquid's not taking away the heat. This means that the glass on one side of the bottle is at a much cooler temperature than the rest of the bottle containing the liquid. Then, when you take the bottle out, because you've had it in the freezer on it's side, and you turn it the right way up, suddenly lots and lots of beer gets in contact with the side that's much colder, which might be enough to kick-start a small crystal forming, which then nucleates it makes it much more energetically favourable for lots of other ice crystals to form and the beer goes slushy.

November 2006