# Temp of beer when calc'ing priming sugar

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#### JasontheBeaver

##### Supporting Member
HBT Supporter
No one seems to address this and I can't find a definitive answer...
My concern is that when using a priming sugar calculator that considers the temp of the beer, is that number going to be accurate no matter what fermentation temperature regimen the beer has gone through?
The theory is that colder beer holds more CO2 in solution than warm beer, and you want to take that into consideration when calculating how much priming sugar to add to achieve your desired carb level.
I understand this basic concept, but what if I've fermented a Belgian at 78F to terminal gravity, then cold crashed it to 30. My argument is that 78F beer won't reabsorb CO2 back into solution in any significant amount. Whereas a lager fermented at 50F then crashed to 30F would contain more CO2.
So for my priming calculator I'm thinking we should enter the highest temperature the beer has experienced after reaching FG, regardless of what the current temp is at bottling.
Thoughts?

Never really thought about it honestly. I don't think it matters unless you are fermenting under pressure. Most CO2 is off gased during fermentation, and I think the differences are probably negligible with various temps. Remember that when you cold crash, you typically do it after fermentation and its not like the beer is grabbing CO2 from the headspace of your carboy.

I've always just used Beersmith for calculating priming sugar so I cant say that I've seen an option for temp input. My guess is that its the temp you will be priming at, and not what fermentation was...

What calculator are you referring to?

This calculation is actually quite simple and has actually been addressed countless times: use the warmest temperature the beer saw once fermentation was complete (FG achieved).
That temperature will have determined the volumes of CO2 the beer could hold. Cold crashing won't change that...

Cheers!

That temperature will have determined the volumes of CO2 the beer could hold.

I don't get this...I feel like you can achieve any level of carbonation with bottle conditioning. Is this trying to factor residual yeast for priming into the calculation?

https://www.northernbrewer.com/priming-sugar-calculator
http://www.brewunited.com/priming_sugar_calculator.php
https://www.morebeer.com/content/priming_sugar_calculator
https://www.hopsteiner.com/co2-calculator/
http://www.homebrewing.com/calculators/?page=tools&section=sugar

Pretty much every calculator asks temp, even Beersmith.

However, I now see that several of these, including a few I listed above DO clarify that they are asking the fermentation temp, not the current temp. This pretty much answers my own question and confirms my theory, it's the temp it was fermented at, not the bottling temp (for the reason you initially mentioned)
Thanks!

This calculation is actually quite simple and has actually been addressed countless times: use the warmest temperature the beer saw once fermentation was complete (FG achieved).
That temperature will have determined the volumes of CO2 the beer could hold. Cold crashing won't change that...
Cheers!
Exactly! I guess I just couldn't find the "countless times". Thanks man!

I don't get this...I feel like you can achieve any level of carbonation with bottle conditioning. Is this trying to factor residual yeast for priming into the calculation?

It's specifically used to determine how much priming sugar is required to raise the intrinsic carbonation level up to goal.
Here's what's actually going on: fermentation creates CO2. Some amount of that CO2 is withheld in the beer. That's determined by temperature - specifically, once fermentation has completed and no further CO2 evolves. The warmer the temperature the beer "sees" post-fermentation, the lower the amount of resident CO2 and the greater the amount of primer required to hit goal...

Cheers!

Huh, I see now and wouldnt have thought it made a difference...I guess it's been a while since I've bottle conditioned and when I did I always just would use 4oz. Never really saw a big difference between colder/warmer fermentation temps honestly...

Yes the proper temperature to enter into the priming calculator is the highest temp the beer has seen since fermentation stopped. The rationale is that the at the end of fermentation, the CO2 level in the beer is in equilibrium with the CO2 in the headspace, and the headspace is assumed to be 100% CO2 (non or minimal leaky fermenter.) Cooling the beer will not create any new CO2 in the beer, so the only way to increase the CO2 in the beer is by reabsorption after cooling. Turns out this is usually insignificant.

Since the beer has a certain level of carbonation already, you only want to add enough priming sugar to cover the delta between the starting carb level and the desired finished carb level.

I did the definitive analysis of how cold crashing affects the CO2 level and you can find it here.

Brew on

I feel like this is still pretty trivial in the grand scheme of bottling...What happens when you rack said beer into your bottling bucket? Not going to lose CO2 during the process?

I guess I've just lost touch with the fine art of bottle conditioning...

I did the definitive analysis of how cold crashing affects the CO2 level and you can find it here.

Well done sir. Very impressive, but my head hurts now...

I feel like this is still pretty trivial in the grand scheme of bottling...What happens when you rack said beer into your bottling bucket? Not going to lose CO2 during the process?

I guess I've just lost touch with the fine art of bottle conditioning...
For a fermentation that finishes at 70°F, the residual CO2 will be 0.81 volumes
For a fermentation that finishes at 50°F, the residual CO2 will be 1.14 volumes
For a temp of 32°F (cold crashed) the equilibrium CO2 will be 1.59 volumes​
If you put your cold crash temp into the priming calculator, you could have a final carbonation level error of 1.59 - 0.81 = 0.78 volumes. which most folks would consider significant.

Some CO2 probably off gases during transfer to a bottling bucket, but it is not possible to calculate this. Some priming calculators might put in a fudge factor in an attempt to compensate for off gasing during transfer.

Brew on

Well done sir. Very impressive, but my head hurts now...
I should have provided a warning.

For a fermentation that finishes at 70°F, the residual CO2 will be 0.81 volumes
For a fermentation that finishes at 50°F, the residual CO2 will be 1.14 volumes
For a temp of 32°F (cold crashed) the equilibrium CO2 will be 1.59 volumes​
If you put your cold crash temp into the priming calculator, you could have a final carbonation level error of 1.59 - 0.81 = 0.78 volumes. which most folks would consider significant.

Some CO2 probably off gases during transfer to a bottling bucket, but it is not possible to calculate this. Some priming calculators might put in a fudge factor in an attempt to compensate for off gasing during transfer.

Brew on

Trust me, I believe you. Lol. I guess I'm just a creature of habit and never put much thought into it before this thread. I can only detect 3 different carb levels: over, under, and juuuust right. Thanks for the education.

Trust me, I believe you. Lol. I guess I'm just a creature of habit and never put much thought into it before this thread. I can only detect 3 different carb levels: over, under, and juuuust right. Thanks for the education.
I'm a geek at heart, and I get off on understanding the physical chemistry, and related calculations, that control the processes involved in brewing. Not something anyone really needs to know to brew great beer.

Brew on

I'm a geek at heart, and I get off on understanding the physical chemistry, and related calculations, that control the processes involved in brewing. Not something anyone really needs to know to brew great beer.

Brew on

That's awesome. I applaud your dedication, and contribution to make things easier for people like me who physics bad...

Well, another thing I didn't consider is you probably wouldn't be bottling at 30F anyway, you want to have the beer at your conditioning temp especially if you're adding fresh yeast.
I've been brewing for years but have just now begun to get back into bottle conditioning in an attempt to take my Belgians to the next level. It's more fun than I thought! I still keg my other beers but as you can tell by my line of questions and out loud thinking, I'm still fine tuning my process and understanding.
Freaking love this hobby.

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