How long does it take to cool a keg of beer?

Question

I have a corny (5 gal) keg of homebrew, already carbonated, that's been aging at room temperature. I'd like to bottle it off soon, but in my experience that works best when the beer is in the 45-50 degree Fahrenheit range.

Tonight the weather forecast for my area says it will get down to 29, and tomorrow it will be right around 45. I'm inclined to just stick the keg on the fire escape tonight and leave it until the afternoon. I'm not really worried about freezing, given the alcohol content I understand it should be able to go down to 28 or 29 without trouble (correct me if I'm wrong here).

I can't seem to find any reliable resources about air cooling, just recommendations for folks trying to cool beer as fast as possible. Will the keg be cool enough tomorrow to bottle?

EDIT: The forecast now says it could get as low as 24, so the freezing question may also be an issue. The keg is outside, so we'll see what happens.

Answer 1

I know I'm a few days late but the worry I'd have leaving a keg outside in cold weather is the pressure changes. CO2 absorbs more in colder conditions, but if anything freezes, even partially, CO2 gets driven out of solution. Normally when you refrigerate kegs indoors they're hooked up to gas, so as pressure in the headspace drops it's less likely the keg will unseal itself. Also, if the keg did freeze a bit the CO2 being forced into the headspace could conceivably go over the pressure limits of the keg, depending on how carbonated it was to begin with among other things.

Think of leaving a bottle or can in the freezer to chill it quickly then forgetting about it. Odds are instead of a beersicle you got beer and glass sprayed all over the inside of your icebox. It's anecdotal, I'll admit, but I've seen it happen so I wouldn't risk a keg and either leave it outside uncarbonated or chill it in a temperature controlled fridge.

Anyway, this is long since past so my fear mongering is moot. Let us know how it went for you. You should be able to leave and accept an answer to your own question and it would be good for the site.

Answer 2

If I want to cool something really quick and not using a fire extinguisher, I use the method I saw on Myth Busters: Find a container that will hold the item you want to chill, add ice, water, and salt. Even on a hot day you can chill things real fast using this method.