# Bottling after cold crashing

#### threefrenchs

##### New Member
I know there is some differences in opinion, but I woud like to get some more thoughts to this senario:
1. Fermented beer at 68 degrees.
2. Crashed beer for 1 week, down to 40 degrees.
3. When calculating priming sugar to you use the 40 degrees in your sugar calculation? Or 68 degrees?

Or ?

Thanks.

Here's Brewer's Friend's input if you haven't seen it.

* Temperature of Beer used for computing dissolved CO2:

The beer you are about to package already contains some CO2 since it is a naturally occurring byproduct of fermentation. The amount is temperature dependent. The temperature to enter is usually the fermentation temperature of the beer, but might also be the current temperature of the beer. If the fermentation temperature and the current beer temperature are the same life is simple.

However, if the beer was cold crashed, or put through a diacetyl rest, or the temperature changed for some other reason... you will need to use your judgment to decide which temperature is most representative. During cold crashing, some of the CO2 in the head space will go back into the beer. If you cold crashed for a very long time this may represent a significant increase in dissolved CO2. There is a lot of online debate about this and the internet is thin on concrete answers backed by research. We are open to improving the calculator so please let us know of any sources that clarify this point.

The equation this calculator uses to compute the amount of dissolved CO2:
CO2 In Beer = 3.0378 - (0.050062 * temp) + (0.00026555 * temp^2)

I would take the average of the two temps - fermenting and crashing - and use that. Then assess the outcome and adjust as needed in your next brew. This way you allow for the influence of both temps in order to arrive at a reasonable compromise target, then you get a baseline result that you can use to develop your strategies going forward.

Where does all this extra dissolved CO2 come from ? there's only a small amount of vented gas still in the headspace , if the chilled beer absorbs that then it will create partial vacuum in the vessel and draw any available gasses in ( air )
i don't crash for more than a week and so set my priming calc to just below the temp for my D - rest ( 18 C in my case )
yet to have an over carbed bottle yet

Been there, done that...if you use a temp lower than the temp during active fermentation, you'll end up with flat beer. I poured a lot of beers out before I got it right.
If your beer finished or rested during secondary at 68, use 68.
For bottle carbing of almost all beers brewed under normal circumstances, if it's not close to an an ounce of table sugar per gallon, it's likely to be undercarbed.
If the fermentation vessel were pressurized, then the CO2 would re-enter solution as temp lowers. Because it's got no pressure, the temp change alone won't pull the CO2 out of the headspace and back into solution in the liquid.

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