dissolved CO2 after fermentation

[mac_1103]

My last couple of bottle conditioned beers have come out a bit undercarbonated. Not flat. Not inconsistent*. Just less bubbly than I wanted/expected. I used 5 ounces of corn sugar for five gallons, which should have given me 2.5-2.6 volumes, but they seem closer to 2.0. So my question is whether there's anything that can change the default assumption of 0.86 volumes of CO2 at 68F after fermentation. I did cold crash these, but brought them back to ambient before bottling.

*Just to preempt the question that many of you will have: I use two different size bottles and I know which were filled first and last. I also use two small PET bottles for the first and last of the batch. So yes, I am sure that the priming sugar was adequately mixed.

 

[day_trippr]

The warmest post fermentation temperature dictates the residual CO2 content. That metric is usually incorporated in carbonation calculators...

Cheers!

 

[mac_1103]

The warmest post fermentation temperature dictates the residual CO2 content.

That's what I thought, so I've been using 68F which is conveniently both the ambient temp of my basement and the default at Brewer's Friend.

 

[hotbeer]

I've got no answer for you. Just some commiseration since I've been seeing the same thing.

When I first started brewing, my first recipe called for using Agave nectar for the priming sugar. And all my wife could find at the store was a big bottle that lasted me up until the last six brews. Those last six brews I used table sugar. They didn't seem as carbonated to the extent that I got with the Agave nectar/syrup.

The current brew I used corn sugar. But they've only been bottled for a week, I need to put one in the fridge to see how it's doing later.

I use the priming sugar calculator from Brewer's Friend. And assumed Agave nectar to be the equivalent of Corn Syrup. So possibly it's more potent and I just got use to seeing more vols of CO2 thinking it was the lesser value I calculated for.

 

[mac_1103]

The warmest post fermentation temperature dictates the residual CO2 content. That metric is usually incorporated in carbonation calculators...

OK, bringing this back because now I think I may have OVER carbed my last batch. It was bulk aged at around 50F for about 4 weeks. So it would have reabsorbed CO2 from the headspace and the crash guard, right? I brought it back to ambient before bottling, but only for about a day so not long enough to re-equilibrate. So now I really have no idea what my starting value for CO2 volumes was.

It's been a week and nothing bad has happened yet. I think the worst case scenario is 3.4 to 3.5 volumes if the brewer's friend calculator is to be believed. And it's in 750 ml Belgian bottles which I believe are rated for that much pressure.

 

[day_trippr]

It was bulk aged at around 50F for about 4 weeks. So it would have reabsorbed CO2 from the headspace and the crash guard, right? I brought it back to ambient before bottling, but only for about a day so not long enough to re-equilibrate. So now I really have no idea what my starting value for CO2 volumes was.

That would make two of us Hopefully nothing dramatic is in store.

Cheers!

 

[doug293cz]

OK, bringing this back because now I think I may have OVER carbed my last batch. It was bulk aged at around 50F for about 4 weeks. So it would have reabsorbed CO2 from the headspace and the crash guard, right? I brought it back to ambient before bottling, but only for about a day so not long enough to re-equilibrate. So now I really have no idea what my starting value for CO2 volumes was.

It's been a week and nothing bad has happened yet. I think the worst case scenario is 3.4 to 3.5 volumes if the brewer's friend calculator is to be believed. And it's in 750 ml Belgian bottles which I believe are rated for that much pressure.

Assuming your system is at atmospheric pressure, and the headspace is 100% CO2, after 4 weeks at 50°F you would have a carbonation level of 1.13 to 1.14 volumes. This compares to 0.84 volumes at the end of a 68°F fermentation, so you are worst case starting with 0.3 volumes "excess" carbonation. To get 3.4 - 3.5 volumes, you would have to have added enough priming sugar to get 3.1 - 3.2 volumes if you didn't have the excess from the cool aging.

Brew on

 

[mac_1103]

Brewer's friend priming calculator says 1.25 volumes after aging and 3.4 with the amount of priming sugar I used.

edit - and maybe not quite that bad according to @doug293cz, who is probably a good deal more reliable than some random online calculator.

edit 2 - I was shooting for ~3 volumes because a) it's a Belgian, b) I had bottles that can handle it, and c) my last few batches have all been under-carbonated when shooting for ~2.5 volumes.

 

[doug293cz]

Brewer's friend priming calculator says 1.25 volumes after aging and 3.4 with the amount of priming sugar I used.

edit - and maybe not quite that bad according to @doug293cz, who is probably a good deal more reliable than some random online calculator.

edit 2 - I was shooting for ~3 volumes because a) it's a Belgian, b) I had bottles that can handle it, and c) my last few batches have all been under-carbonated when shooting for ~2.5 volumes.

I looked at the Brewers Friend Priming Calculator, and they use this polynomial to calculate residual CO2 volumes post fermentation (which assumes 0 psi gauge pressure):

Volumes = 3.0378 - (0.050062 * temp) + (0.00026555 * temp^2)​

​

I use a formula recommended by A J deLange (link to paper broken, but paper attached below.) The formula is:

Volumes = (Pressure + 14.695) * (0.01821 + 0.090115 * exp ( - (Temp - 32) / 43.11)) - 0.003342​

​

Where for both cases temp is in °F, and pressure is in PSI gauge. The deLange paper gives max error for its formula as -0.044 volume, and RMS error at 0.01 volume, so it's pretty accurate.

I charted the outputs of the two formulas below, and the error in the Brewers Friend formula looks to be much worse than the deLange formula.

Also, I had to set the temp to 48°F in Brewers Friend to come up with a residual CO2 level of 1.25 volumes.

Brew on

 

[mac_1103]

Also, I had to set the temp to 48°F in Brewers Friend to come up with a residual CO2 level of 1.25 volumes.

That's true. My temperature control isn't that great, but my temperature monitoring is excellent. The fridge in question fluctuated between 48 and 51 over those four weeks, so I took the worst case.

Thanks for the help and all the hella good maths!.