Amount Of CO2 Remaining After 17 Months

[SourLover]

I have 5 gallons of golden sour that's been sitting for about 17 months. My plan is to transfer 3 gallons onto tart cherries, and then bottle the balance of the base beer.

The calculator that I use says the remaining CO2 in the beer is 0.83 volumes, but after 17 months that doesn't seem like a good number. Does anyone have an guess as to how much might be remaining, or perhaps someone has a formula/method that they use? I'd really like to get the carbonation right on the base beer as it has turned out very well.

For the 3 gallons that is going to referment I'm assuming that the 0.83 volumes is a good number to use.

 

[SanPancho]

its temperature dependant. basically, how much was retained by beer while yeast were fermenting. if i recall its based on the warmest fermentation temp, as once it starts cooling it doesnt give up co2 unless you do something to it, i.e. splash it, shake it up, etc. etc.

so it should be the same as when you sealed it up. (assuming it was fully sealed container)

 

[SourLover]

its temperature dependant. basically, how much was retained by beer while yeast were fermenting. if i recall its based on the warmest fermentation temp, as once it starts cooling it doesnt give up co2 unless you do something to it, i.e. splash it, shake it up, etc. etc.

so it should be the same as when you sealed it up. (assuming it was fully sealed container)

Science wasn't my strong suit, but if I ferment a beer in 2-3 weeks I can agree with the calculator as to what amount of CO2 is left in solution. Now, if I have that same beer, but it has been in a fermenter for 17 months, and has been sitting at 1.004 for at least 10 months, if the air lock bubbles every so often doesn't that have to be CO2 coming out of solution and thus lowering the amount of CO2 remaining in the beer?

 

[SanPancho]

yes. however the question is why?

your pressure is effectively zero. open to atmosphere. so the only variable is temperature.

if some tiny little brett or even lacto is still crawling along then its just co2 produced that is in excess of your equilibrium co2 volume at a given temperature.

otherwise it could be from the beer getting warmed and giving up some co2, as warmer temps means less solubility of co2 at any given pressure.

the question is- how stable has the temps been for this beer? more fluctuations means more problems and less co2

 

[doug293cz]

Science wasn't my strong suit, but if I ferment a beer in 2-3 weeks I can agree with the calculator as to what amount of CO2 is left in solution. Now, if I have that same beer, but it has been in a fermenter for 17 months, and has been sitting at 1.004 for at least 10 months, if the air lock bubbles every so often doesn't that have to be CO2 coming out of solution and thus lowering the amount of CO2 remaining in the beer?

No, the airlock can bubble just to to gas expansion from temperature rise. Which means you can also get air suck back when the temp cools. As the number of cycles increases the amount of CO2 in the headspace goes down, and CO2 comes out of the beer to maintain equilibrium with the CO2 partial pressure in the headspace. The total pressure in the headspace remains constant at about 14.7 psi (absolute), so as air works its way back into the headspace, the partial pressure of CO2 continually goes down.

Eventually, your beer will go completely flat. Where it is after 17 months is anyone's guess. If it were my beer, I would assume that it has no residual CO2. I don't know if any of the on-line priming calculators can handle that situation.

Brew on

 

[SourLover]

No, the airlock can bubble just to to gas expansion from temperature rise. Which means you can also get air suck back when the temp cools. As the number of cycles increases the amount of CO2 in the headspace goes down, and CO2 comes out of the beer to maintain equilibrium with the CO2 partial pressure in the headspace. The total pressure in the headspace remains constant at about 14.7 psi (absolute), so as air works its way back into the headspace, the partial pressure of CO2 continually goes down.

Eventually, your beer will go completely flat. Where it is after 17 months is anyone's guess. If it were my beer, I would assume that it has no residual CO2. I don't know if any of the on-line priming calculators can handle that situation.

Brew on

yes. however the question is why?

your pressure is effectively zero. open to atmosphere. so the only variable is temperature.

if some tiny little brett or even lacto is still crawling along then its just co2 produced that is in excess of your equilibrium co2 volume at a given temperature.

otherwise it could be from the beer getting warmed and giving up some co2, as warmer temps means less solubility of co2 at any given pressure.

I'm thinking it is almost flat. If I'm shooting for 3.5 volumes and the calculator says I have 0.83 volumes of residual CO2 then I'm assuming that if I followed the calculator I'd end up with 2.67 volumes (3.5 - 0.83). Is that math correct? If it is, I'm just going to shoot for right around 4 volumes and I should end up in the range that I want to be at.

 

[doug293cz]

I'm thinking it is almost flat. If I'm shooting for 3.5 volumes and the calculator says I have 0.83 volumes of residual CO2 then I'm assuming that if I followed the calculator I'd end up with 2.67 volumes (3.5 - 0.83). Is that math correct? If it is, I'm just going to shoot for right around 4 volumes and I should end up in the range that I want to be at.

If it has gone flat, then to get 3.5 volumes, but the calculator assumes you have 0.83, then you need to target 3.5 + 0.83 = ~ 4.3 volumes. In any case telling the calculator 4.0 should be better than telling it 3.5.

Brew on

 

[SanPancho]

thats a tough one. you really only get one shot at this since its going into bottles. i'd say why not. if you're wrong and you have zero co2 now, you'll wind up with about 2.7 which is more like lager/wheat territory. not the end of the world.

 

[SourLover]

If it has gone flat, then to get 3.5 volumes, but the calculator assumes you have 0.83, then you need to target 3.5 + 0.83 = ~ 4.3 volumes. In any case telling the calculator 4.0 should be better than telling it 3.5.

thats a tough one. you really only get one shot at this since its going into bottles. i'd say why not. if you're wrong and you have zero co2 now, you'll wind up with about 2.7 which is more like lager/wheat territory. not the end of the world.

Thanks so much for the feedback. I now have a plan for this batch, and also going forward.

 

[DuncB]

You will also get airlock action with changes in atmospheric pressure as well as temperature.
I'd reckon your beer is flat and aim to prime for 4 vols as @doug293cz suggests.

 

[Brewdog80]

Beer is dead flat after this amount of time. The residual would be as close to zero as an open beer in a glass after a week.... add to get to what you desire

 

[Dr_Jeff]

It might need additional yeast, something like CBC-1, but its anyone's guess at this point.

 

[SourLover]

DuncB & Brewdog80 thank you for your comments.

It might need additional yeast, something like CBC-1, but its anyone's guess at this point.

Most definitely. I use Red Star Premier Cuvee (blue packet) on all of the sours that I bottle. CBC-1 works great for me on the high ABV dark beers that I bottle, but I haven't tried it on any sours yet.

 

[whattabrau]

Taste it. The sensory threshold for CO2 is about 500mg/L (0.25 volumes). If it tastes completely flat, you know you're at below that, and can approximate it as zero. If it doesn't taste completely flat, you know you're somewhere between 0.25 and the calculator. If you want to further narrow it down, taste a freshly finished beer and try to guess how much below, if at all, your sour is. Though, the higher the carbonation you're aiming for, the less the accuracy for the residual CO2 matters.

Now, even if the hydrometer has remained at a steady 1.004 for 10 months -- and I'm not convinced you can read steady to that precision with a homebrew instrument -- it doesn't mean the airlock bubbles aren't a result of fermentation. Let's do some back-of-the-envelope and say it's a 1mL bubble, i.e. about 1.25mg CO2. You need about 2.5mg extract to create 1.25mg CO2. For 5gal (~20kg), with 0.001 = 0.20 plato (+), you use about 20kg * 0.0020 = 40g extract per 0.001 of fermentation. In other words, you have 40000/2.5 = 16000 bubbles per 0.001. Over 300 days, that's still over 50 bubbles per day, which is several per hour. (plus or minus whatever the actual airlock bubble size is, but I'm pretty sure the order of magnitude in my calculation is correct)

+) real attenuation is about 80% of apparent attenuation, hence 80% of the usual 4pts = 1 degree plato.

 

[DuncB]

Now that is the kind of thing I like, guessed bubble volume and then some numbers.
Does it fizz?