Fermzilla

[Ian Mackenzie]

AS your beer is already partially carbonated, try 40PSI and shake the keg for a few minutes. Reduce to 30PSI and leave for about 5 hours. Reduce to serving pressure and an hour or so, pour a beer. If still not enough carb, raise pressure to 30PSI for a few more hours. You will soon get the hang of it. There are online tools for calculating "set and forget" carbonation settings but these are not much use if your beer is already partially carbonated and you want to quickly do a forced carb.

Thanks for that

 

[Grmblz]

Thanks for that

If your beer is at 12psi it's already pretty much carbonated, it's easy to add a bit of carbonation but a pain if you over do it.
What's your serving pressure? If it's 12-15psi then just connect gas at that pressure as you chill, once chilled do a test pour, if it's a bit flat then do as Vic says but in little steps, it's remarkably easy to over carbonate, and then it's a right royal pita.

 

[Vic]

If your beer is at 12psi it's already pretty much carbonated, it's easy to add a bit of carbonation but a pain if you over do it.
What's your serving pressure? If it's 12-15psi then just connect gas at that pressure as you chill, once chilled do a test pour, if it's a bit flat then do as Vic says but in little steps, it's remarkably easy to over carbonate, and then it's a right royal pita.

That is as long as you are cooling the beer to about 2C. If you’re warm conditioning then it’s different.

 

[pauly]

If your beer is at 12psi it's already pretty much carbonated, it's easy to add a bit of carbonation but a pain if you over do it.
What's your serving pressure? If it's 12-15psi then just connect gas at that pressure as you chill, once chilled do a test pour, if it's a bit flat then do as Vic says but in little steps, it's remarkably easy to over carbonate, and then it's a right royal pita.

Unfortunately 12PSI at 20c works out at about 1PSI at 5c.

@Ian Mackenzie if you have no need to drink the beer immediately, then transfer it to the keg, put it in the fridge, and just apply it at 12PSI for a few weeks. The coopers kit will probably benefit from a few weeks of sitting/cooling before drinking it. It's super easy to over carb a beer when force carbonating, but very easy to just let the beer absorb the co2 over a few weeks.

If you haven't already transferred it Gash at the home brew network has some good videos on enclosed transfers from FZ to a keg.

cheers, good luck!

 

[Grmblz]

Unfortunately 12PSI at 20c works out at about 1PSI at 5c.

Yep, which is why I said hook it up to 15psi as you chill, and use Vic's method if it's still a bit flat, I don't know of many keggers happy to wait a few weeks.

 

[theSeekerr]

Unfortunately 12PSI at 20c works out at about 1PSI at 5c.

No it doesn't?

12 psig at 20C is 26.7psia at 293.15K
5C is 278.15K

The absolute pressure will reduce proportionally to the absolute temperature. (278.15/293.15) * 26.7 = 25.3 psia = 10.63 psig

In reality you'll see it read a tiny bit lower than that after cold crash - the increased solubility of CO2 in cold beer will see some of it enter solution, and there's a tiny bit of volume change attributable to the contraction of the liquid as it cools. All the same, you cold crash a beer at 12 psig you're going to be seeing 9+ PSI, not "about 1PSI".

 

[Vic]

No it doesn't?

12 psig at 20C is 26.7psia at 293.15K
5C is 278.15K

The absolute pressure will reduce proportionally to the absolute temperature. (278.15/293.15) * 26.7 = 25.3 psia = 10.63 psig

In reality you'll see it read a tiny bit lower than that after cold crash - the increased solubility of CO2 in cold beer will see some of it enter solution, and there's a tiny bit of volume change attributable to the contraction of the liquid as it cools. All the same, you cold crash a beer at 12 psig you're going to be seeing 9+ PSI, not "about 1PSI".

Very close to my observations, I have not done the calculations but a Kolsh still in the fermenter started slow ramp over 24 days from 17C to 2C. At 17C pressure was 12PSI, today at 2C it is as 7PSI. A sample shows considerable carbonation but it will need more.

 

[pauly]

Yep, which is why I said hook it up to 15psi as you chill, and use Vic's method if it's still a bit flat, I don't know of many keggers happy to wait a few weeks.

sorry, I must have completely mis-read your comment!

 

[pauly]

No it doesn't?

12 psig at 20C is 26.7psia at 293.15K
5C is 278.15K

The absolute pressure will reduce proportionally to the absolute temperature. (278.15/293.15) * 26.7 = 25.3 psia = 10.63 psig

In reality you'll see it read a tiny bit lower than that after cold crash - the increased solubility of CO2 in cold beer will see some of it enter solution, and there's a tiny bit of volume change attributable to the contraction of the liquid as it cools. All the same, you cold crash a beer at 12 psig you're going to be seeing 9+ PSI, not "about 1PSI".

I use this chart, and as I read it 12PSI gives me ~1.5 volumes of CO2 at 20C, which works out to ~1PSI at 2C. I am happy to be corrected if I am reading the chart wrong, however I pressure ferment at 10PSI at around 20C, and when I cold crash the FZ to 2C my gauge goes down to 2/3PSI. I have done one ferment at 25PSI and then after cold crashing the gauge was at 10PSI.

Again, happy to be corrected if I am misunderstanding the chart, or if the science is wrong.

 

[Grmblz]

sorry, I must have completely mis-read your comment!

No problem mate, and thank you to our learned friends ^^ for the science, I'm not particularly scientific and happy to bow to superior knowledge, but I do know what works in some instances, and if my simplistic approach (useful for people just getting into it) can be of assistance then so be it.
Cheers G

 

[Ian Mackenzie]

Thanks for all that info everyone and also the chart pauly.

 

[theSeekerr]

I use this chart, and as I read it 12PSI gives me ~1.5 volumes of CO2 at 20C, which works out to ~1PSI at 2C. I am happy to be corrected if I am reading the chart wrong, however I pressure ferment at 10PSI at around 20C, and when I cold crash the FZ to 2C my gauge goes down to 2/3PSI. I have done one ferment at 25PSI and then after cold crashing the gauge was at 10PSI.

Again, happy to be corrected if I am misunderstanding the chart, or if the science is wrong.

You're not wrong. The confusion arises because we're comparing apples and oranges - headspace equilibrium pressure for a given level of carbonation vs behaviour of gas at different temperatures. The two physical phenomena don't react to temperature changes in the same way. Furthermore, the carbonation level takes hours or days to settle on a final value, while the drop in pressure proportional to temperature takes place more or less instantaneously - I think it's this second point that's causing some confusion.

If you take a beer that has sat at 12 PSI at 20C for long enough to reach equilibrium then yes, it will be carbonated to 1.5 volumes.

If you cold-crash it the equilibrium changes, but the total amount of gas in the container does not

For argument's sake, let's imagine a 27L FermZilla with 20L of beer and 7L headspace which has been spunded at 12 PSI @ 21C, and let's round the resulting 1.49 volumes CO2 to 3g/L

So in total the container has:
3g/L * 20L = 60g dissolved CO2
+ 7L @ 26.7 psia @ 294.15K CO2 = 0.5269 moles = 23.2g CO2 gas
= 83.2g total CO2

Now let's cold-crash that to 2C / 275.15K

If we could crash-chill instantly, then in that instant we'd still have 3g/L = 60g dissolved CO2 in the beer, and we'd have headspace pressure of
26.7 psia * (275.15 K / 294.15 K ) = 25 psia = 10.3 psig , so that's our upper bound on pressure and lower bound on carbonation.

Conversely, if all the CO2 dissolved in the beer (0 psi absolute, or -14.7 psi gauge!) you'd have 83.2 / 20 = 4.16g/L ~= 2.08 volumes CO2, so there's the upper bound on carbonation and lower bound on pressure.

The equilibrium must exist between those figures. The relevant part of the Carbonation chart:

Where those values at 2C are for pressures of 0-6 psi gauge.

Using the equations we can work out what the headspace pressure would be for any level of dissolved CO2. So I pulled out Excel and did that, and here's the relevant region:

At 1.72 vols, the chart says 2 psi, and I calculate we only have enough CO2 for 0.8 psi in the headspace, so it's not quite that high.

Conversely, to get down to 1 psi in the headspace I calculate the beer would have to have dissolved 1.71 vols, a bit more than the 1.62 vols indicated by the chart as the equilibrium for that pressure.

Thus we know the true value exists in between those pairs of figures - between 1-2 psi and 1.69 - 1.72 volumes of CO2

So you're absolutely correct - on a long enough time scale, you'd expect a fermenter cold-crashed from 12 psi at 21C down to 2C to settle a bit below 2 psi.
Conversely, on a short timescale I'd expect a fermenter just recently crashed from 12 psi at 21C down to 2C to be reading a bit less than 10 psi, gradually approaching 2 psi over several more days.

I really hope that's helpful because it took ages to write up.

 

[Ian Mackenzie]

You're not wrong. The confusion arises because we're comparing apples and oranges - headspace equilibrium pressure for a given level of carbonation vs behaviour of gas at different temperatures. The two physical phenomena don't react to temperature changes in the same way. Furthermore, the carbonation level takes hours or days to settle on a final value, while the drop in pressure proportional to temperature takes place more or less instantaneously - I think it's this second point that's causing some confusion.

If you take a beer that has sat at 12 PSI at 20C for long enough to reach equilibrium then yes, it will be carbonated to 1.5 volumes.

If you cold-crash it the equilibrium changes, but the total amount of gas in the container does not

For argument's sake, let's imagine a 27L FermZilla with 20L of beer and 7L headspace which has been spunded at 12 PSI @ 21C, and let's round the resulting 1.49 volumes CO2 to 3g/L

So in total the container has:
3g/L * 20L = 60g dissolved CO2
+ 7L @ 26.7 psia @ 294.15K CO2 = 0.5269 moles = 23.2g CO2 gas
= 83.2g total CO2

Now let's cold-crash that to 2C / 275.15K

If we could crash-chill instantly, then in that instant we'd still have 3g/L = 60g dissolved CO2 in the beer, and we'd have headspace pressure of
26.7 psia * (275.15 K / 294.15 K ) = 25 psia = 10.3 psig , so that's our upper bound on pressure and lower bound on carbonation.

Conversely, if all the CO2 dissolved in the beer (0 psi absolute, or -14.7 psi gauge!) you'd have 83.2 / 20 = 4.16g/L ~= 2.08 volumes CO2, so there's the upper bound on carbonation and lower bound on pressure.

The equilibrium must exist between those figures. The relevant part of the Carbonation chart:
View attachment 118310
Where those values at 2C are for pressures of 0-6 psi gauge.

Using the equations we can work out what the headspace pressure would be for any level of dissolved CO2. So I pulled out Excel and did that, and here's the relevant region:

View attachment 118309

At 1.72 vols, the chart says 2 psi, and I calculate we only have enough CO2 for 0.8 psi in the headspace, so it's not quite that high.

Conversely, to get down to 1 psi in the headspace I calculate the beer would have to have dissolved 1.71 vols, a bit more than the 1.62 vols indicated by the chart as the equilibrium for that pressure.

Thus we know the true value exists in between those pairs of figures - between 1-2 psi and 1.69 - 1.72 volumes of CO2

So you're absolutely correct - on a long enough time scale, you'd expect a fermenter cold-crashed from 12 psi at 21C down to 2C to settle a bit below 2 psi.
Conversely, on a short timescale I'd expect a fermenter just recently crashed from 12 psi at 21C down to 2C to be reading a bit less than 10 psi, gradually approaching 2 psi over several more days.

I really hope that's helpful because it took ages to write up.

Thanks the seekerr for the time you have taken to explain in detail the answer to my question. I think I get the basic idea. and practice will make perfect.

 

[pauly]

@theSeekerr I appreciate the write up, I did think the headspace of the FZ would contribute somewhat but I didn't expect it to add so much CO2. I normally cold crash for 2-3 days due to life getting in the way of brewing, so that explains the PSI readings I see.

I serve a bit warmer and flatter than most, 7C and 10PSI in the kegerator, so it looks like I get almost all of the initial carbing from the headspace CO2, which is kind on my gas bottle.

Again, thanks for the writeup.

 

[Nullnvoid]

Another successful batch with no issues.

What am I doing wrong, dag nammit!

 

[wide eyed and legless]

Another successful batch with no issues.

What am I doing wrong, dag nammit!

So the 9th PF, early days yet.

 

[Nullnvoid]

So the 9th PF, early days yet.

And 16th ferment in the Fermzilla

 

[wide eyed and legless]

And 16th ferment in the Fermzilla

Are you counting this one.

 

[Nullnvoid]

Are you counting this one.
View attachment 118326

Yep. That was still successful. Beer was made.

That was one of my first and my own stupid fault. In a way the Fermzilla performed admirably and vented because of what I did wrong.

I now know what to do and it works. Every. Single. Time.

 

[malt and barley blues]

I think its luck of the draw, this one blew at 10 PSI first time he used it. Simple pressure testing would eliminate all this.