Question about priming sugar

[adamgm]

I found this comment in an old thread on this forum. I was wondering if someone could explain why this is the case?

I'm considering getting a 3 gallon keg for my homebrew, I was planning on getting a C02 tank, but this was something I wasn't aware of.

The quote:

Keep in mind, if you force carb in a keg it should be cold, but carbing with sugar the keg should be warm. You can also use malt in place of sugar to carb.

Does this mean the keg MUST always be in a fridge (or similar) for some reason if you are doing forced carbonation?

 

[Elric]

refer to a carbonation chart, there are tons of them out there so I'm not going to bother linking one. The crux of it is is that the warmer your liquid, the higher the psi you have to have going into your liquid to carbonate it to the volume you want, so force carbonating at chilled temperatures makes way more sense. These aren't the exact numbers, but close enough to give you an idea. To carbonate to 2.5 volumes a beer at 38f needs 12psi applied. The same beer at 68f would require 28psi applied to achieve the same volume. When you also consider that the warmer a beer is, the faster it starts to degrade, it just makes sense to chill it as soon as yeast activity is no longer required.

 

[adamgm]

refer to a carbonation chart, there are tons of them out there so I'm not going to bother linking one. The crux of it is is that the warmer your liquid, the higher the psi you have to have going into your liquid to carbonate it to the volume you want, so force carbonating at chilled temperatures makes way more sense. These aren't the exact numbers, but close enough to give you an idea. To carbonate to 2.5 volumes a beer at 38f needs 12psi applied. The same beer at 68f would require 28psi applied to achieve the same volume. When you also consider that the warmer a beer is, the faster it starts to degrade, it just makes sense to chill it as soon as yeast activity is no longer required.

Thanks for the reply.
At the moment, I’ll have no way to refrigerate the keg I would like to get, so my plan is to leave it unchilled, I assume it’s better for the beer to not chill it for forced carb and then let it warm up?
My plan for the short term would be to perhaps pour some beer into a growler or two when bringing some beer with me.

 

[VikeMan]

Just to add...
What @Elric said is correct, i.e. the set-and-forget PSI needed to reach and hold at equilibrium for X volumes of beer is temperature dependent. However, this doesn't mean that you'll be using significantly more CO2 (by weight) to carbonate the beer at higher temps. The same amount of CO2 will ultimately be dissolved in the beer. (And the difference in CO2 in the headspace will be small.)

 

[adamgm]

Just to add...
What @Elric said is correct, i.e. the set-and-forget PSI needed to reach and hold at equilibrium for X volumes of beer is temperature dependent. However, this doesn't mean that you'll be using significantly more CO2 (by weight) to carbonate the beer at higher temps. The same amount of CO2 will ultimately be dissolved in the beer. (And the difference in CO2 in the headspace will be small.)

Thanks!
I was assuming that the difference in what's required between room temp and refrigerator temp would be fairly insignificant.

Edit: looks like I'm wrong, it seems to go up by about 25 PSI. Kegging may not be doable for me after all.

 

[VikeMan]

Edit: looks like I'm wrong, it seems to go up by about 25 PSI. Kegging may not be doable for me after all.

I'm not following. Are you saying your regulator won't allow a high enough pressure?

 

[adamgm]

I'm not following. Are you saying your regulator won't allow a high enough pressure?

No, sorry. it seemed like a pretty high temperature to have to leave something, but I'm realizing I'm not sure for how long it's required.

 

[T Murph]

Maybe this will simplify it for you. The pressure in a Co2 tank at room temperature is, for example sake, 2600 psi. Put that Co2 tank in a refrigerator over night and the now cold Co2 tank pressure is 1300 psi. No Co2 has been lost it has simply condensed. Leave that same keg out of refrigeration over night and the now warm tank of Co2 has returned to 2600 psi. The same principle is true with your beer. Cold beer and warm beer should contain the same volume of Co2 but the pressure will differ.

 

[hotbeer]

Title and question at end of OP don't quite match, but I would think that if using priming sugar to carbonate the beer in the keg, then you'd have it at higher temps till after the priming sugar is consumed. Typically 2 weeks.

Might also be something to keeping the keg warmer to provide pressure to push the beer out if no CO2 tank used to pressurize the system. Is that ever done?

But I've never kegged. I am curious just for if I ever do keg.