Cold crashing and bottling temperature?

[mcleanmj]

I bottle my beer. I've never done a cold crash, but would like to try cold crashing an IPA I've got fermenting. I use Northern Brewer priming sugar calculator, which determines sugar quantity based on the current beer temperature (by calculating CO2 already dissolved in the beer). If I cold crash close to freezing and then bottle the beer in my 70 degree kitchen, the beer will warm up by several degrees while bottling. So if I base my sugar amount on 34 degrees F but half the beer isn't packaged until its reached 50 F, how much of a problem could I have? Alternatively, should I just let the beer warm back up to room temperature after the cold crash prior to bottling?

Thanks a lot!

 

[Yooper]

You can bottle it cold, no worries!
However, you don’t use the current beer temperature; you use the highest temperature that the beer reached during/after fermentation. That’s because while co2 is held in the liquid at lower temperatures, more c02 wouldn’t be produced.
I hope that makes sense! If the beer reached 68 degrees as fermentation slowed/finished, than use that.

 

[McKnuckle]

To expand further, perhaps more than you need:

During fermentation while CO2 is still being produced, the amount of CO2 that stays in the beer varies with temperature. The colder it is, the more CO2 stays in solution. As fermentation warms up, more CO2 escapes into the headspace. CO2 that exceeds the headspace leaves via the airlock once the slight amount of pressure required to burp the airlock is present.

Once CO2 production ceases, that slight pressure drops back to nil, and the beer and the headspace reach equilibrium. At this point, if you warm up the beer, more CO2 will come out of solution and escape. But conversely, if you cool it down, CO2 will not magically diffuse back into the beer (unless it's pressurized). It can decrease, but not increase. That's why you must use the highest temperature that the beer reached in the fermenter in the equation.

 

[mcleanmj]

Great, thank to both of you! That makes a lot more sense. I've noticed that Brewfather specifically states "highest temperature reached during fermentation" whereas Northern Brewer states "current temperature of the beer." The fact that presently dissolved CO2 should be based on the max temp ever achieved due to max CO2 escape makes total sense.

Much appreciated and cheers!

 

[Brooothru]

Great, thank to both of you! That makes a lot more sense. I've noticed that Brewfather specifically states "highest temperature reached during fermentation" whereas Northern Brewer states "current temperature of the beer." The fact that presently dissolved CO2 should be based on the max temp ever achieved due to max CO2 escape makes total sense.

Much appreciated and cheers!

Me too. I seldom bottle condition more than a few, based on what's left over after I keg an unspunded beer. I use the MoreBeer calculator since I can solve for virtually any volume of leftovers, down to a few ounces of beer and grams of corn sugar. I just blindly would follow the instructions to "use the current temperature of the beer" in the calculation without even considering the underlying physics.

No wonder my bottled leftovers always seemed a little flat.

Brooo Brother