When using CO2 calculators or the nomograph on Palmer's site we see that depending on the temperature of your beer, you use a different amount of priming sugar in order to get the same effective carbonation. Why would temperature effect the amount of CO2?

My (incorrect) logic goes like this: You put "X" number of yeast cells into a bottle with "Y" amount of food. When the yeast are done, you have "Z" CO2. So if you do two bottles, both with X and Y counts, and one bottle is warmer, then all of the food might get consumed sooner (presuming both temperatures are keeping the yeast happy), and you get Z CO2. But the cooler bottle, once all the food is gone, should also have Z CO2, not Z plus something.

So what is going on that changes the food to CO2 ratio when temperature changes?

  • 1
    It's not the temperature of bottle conditioning, it's the temperature of the fermented beer that you're adding priming sugar to.
    – baka
    Jun 10, 2012 at 16:33

1 Answer 1


What you're not accounting for is the CO2 produced during fermentation. The colder the beer ferments, the more CO2 will be in solution in it. That kinda gives you a "head start" on carbonation. If you don't account for the CO2 retained, your beer can be either over or under carbonated.

  • So when bottling lagers, would you say its a good rule of thumb to bring them up to room temp for a day or two before bottling, to let that extra C02 in suspension bubble out? That way, say, 4oz of Dextrose will give you the same carbonation in a lager as in an ale?
    – GHP
    Jun 11, 2012 at 12:55
  • Very smart Denny! Excellent. Not sure why I didn't think of that, but makes perfect sense.
    – Dale
    Jun 11, 2012 at 14:27
  • Graham, that's what I do. It's not 100% effective, but I find it easier than trying to figure out how much dissolved CO2 is in the beer. Yeah, I know, I'm lazy....
    – Denny Conn
    Jun 11, 2012 at 14:49
  • co2 is solvent in solutions. the cooler the temperature of the liquid the more co2 can be absorbed. another reason why you want to chill your brew before opening. Jun 12, 2012 at 12:04

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