I am watching the Stoke vs Swansea game, & to be honest, it's pretty boring. So much so, that I've started to wonder why it is that my beer has turned into a slushy after being taken out of the freezer.

I bought it this morning, it wasn't very cold, so just before the game I put it in the freezer to achieve optimal freshness. Started off pretty well, but rather than getting warmer as I drink, it's actually continued to freeze.

I am in France.

The windows are open.

It's 22 degrees Celsius.

I have attached a pic of the beer in question.

enter image description here

Have I discovered the holy grail of beer chilling?

  • $\begingroup$ Was it liquid when you took it out of the freezer? $\endgroup$ Oct 19, 2014 at 16:23
  • $\begingroup$ Yes. More liquid than it is now. $\endgroup$
    – Dan
    Oct 19, 2014 at 16:23
  • 1
    $\begingroup$ Like this? youtube.com/watch?v=Fot3m7kyLn4 $\endgroup$
    – Ajedi32
    Oct 20, 2014 at 14:12

4 Answers 4


When you opened the beer, carbon dioxide was lost to the atmosphere, increasing the mole fraction of water in the beer and raising its freezing point to a point above the temperature of the beer. Not all of the water froze, leaving it a slush.

Edit: There's also the possibility that the loss of CO2 from the solution is not the issue. It could just be that when you opened the beer you disturbed a supercooled solution enough to start it freezing.

2nd edit: Instead of continuing the comments I'll add here. The freezing on the outside of the can shows that the temperature of the beer is below the freezing point of water. Is the temperature of the beer lower than the freezing point of the beer? If it were, the beer should freeze instantly upon being disturbed. If the beer is above its freezing point, but the loss of CO2 raises the freezing point it should freeze gradually as it sits out.

  • $\begingroup$ Within a minute, ice that wasn't there initially has appeared on the can $\endgroup$
    – Dan
    Oct 19, 2014 at 16:37
  • $\begingroup$ 3 minutes later, can is COVERED by a layer of ice $\endgroup$
    – Dan
    Oct 19, 2014 at 16:40
  • $\begingroup$ If the beer freezes as soon as you open it, then it is most likely a supercooled solution that froze upon being disturbed. If it takes time to freeze, it is most likely the loss of CO2 from the solution. $\endgroup$ Oct 19, 2014 at 16:40
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    $\begingroup$ @brinnb You can take beer out of the freezer and shake it and it will remain liquid. The moment you open it, it will start to freeze up. The release of pressure changes the temperature when water freezes. See the phase diagram for water. The release of $\ce {CO2}$ would increase the freezing point, not lower it. $\endgroup$
    – LDC3
    Oct 19, 2014 at 17:06
  • 2
    $\begingroup$ @LDC3 The effect of pressure on the freezing point is really subtle (13.35 MPa gives a melting point of -1 °C www1.lsbu.ac.uk/water/density_anomalies.html#Pmelt). The curve is very steep physics.stackexchange.com/questions/60170/… The release of CO2 changes the freezing point somewhat, but more important is the heat release, not the change of the freezing point. $\endgroup$ Oct 20, 2014 at 13:33

As you can see in the phase diagram for water, higher pressures decrease the freezing point.

From Chemwiki:

one is able to melt ice simply by applying pressure and not by adding heat.

When you open the beer, you release the pressure in the bottle, raising the freezing point of the beer, so it starts to freeze. Since the bottle is colder than the freezing point of water, any water condensing on the outside will freeze.

BTW, the release of $\ce {CO2}$ from the beer will actually raise the freezing point, not lower it.


The pressure inside the can/bottle is higher than the atmospheric pressure and due to this higher pressure, the freezing point of the beer increases. When you opened the can/bottle, the pressure of the beer equals the atmospheric pressure, decreasing the freezing point of the beer and hence, starting to freeze.



There are multiple physical forces at work here. Pick'em out and list them.

You got "gas laws" available from elementary chemistry texts.

You got $\ce{CO2}$ dissolved in liquid - escaping (Mole laws, antifreeze effect, or not; suppression of freezing &/or boiling point(s)). Note: When gas leaves a container (beer can, bug spray, fire extinguisher, etc.), it cools the container and what's in it, even though other forces resist temperature change, i.e., freezing due to the solubility of the gas in the water/alcohol fraction, et al. of the beer.

Heard of "equilibrium", "function" (Fx), "ambient temp."? The frost on the outside comes from atmospheric water (water vapor) collecting and freezing on the cold container. As the system warms up (out of the frig), this ice will melt.

The aforementioned does not claim to be a complete account of what's going on here.


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