Fermenting under Pressure + Chilling

[jonbrout]

Been out of the game for a few years, Starting back with smaller batches, and fermenting under pressure.

I haven't been able to find the answer to / a calculator that describes what PSI you would need to ferment at if you are cold crashing to a specific temp afterwards. Shooting for around 2.4ish Vol of CO2 in the end (chilled) product.



Example: I am fermenting under pressure at 70*, at what Pressure should I ferment at (spunding) if I want the end product to contain 2.4 Vol. Of C02 when I chill it to 40 Degrees?



Thanks for your help!

 

[Jim R]

https://drhansbrewery.com/beercarbonationcalculator/
This is what I use.

 

[jonbrout]

Thank you for your time, but I do not believe that's quite what I'm asking.
More specifically, I am asking how you would know what the final C02 vol. is in the Chilled beer if you are Fermenting at a different temp and at a specific pressure.

I reason that as it is cooled, the CO2 absorption will increase into the liquid as the temp decreases and thus the carbonation tables and Calcs do not take this into effect.

 

[DuncB]

Me too, works well. I often start with only a few psi on the spunding valve and then crank it up after the krausen has fallen. But pressure is also a good way to keep the head in the vessel rather than all over the place.

 

[Jim R]

Thank you for your time, but I do not believe that's quite what I'm asking.
More specifically, I am asking how you would know what the final C02 vol. is in the Chilled beer if you are Fermenting at a different temp and at a specific pressure.

I reason that as it is cooled, the CO2 absorption will increase into the liquid as the temp decreases and thus the carbonation tables and Calcs do not take this into effect.

If I am understanding correctly, you don't want to set the fermentation pressure based on what you want after cold crashing (ie 40 degrees). Set it for your actual fermentation pressure (70 degrees if that is your goal).

For me (and probably most people), we would then transfer the beer to the keg to cold crash, remove the spunding valve, attach the CO2 tank and set the regulator to the desired pressure for the refrigerator temperature.

 

[Vale71]

This is the calculator you're looking for although I'm afraid you're missing the actual point of pressure fermentation which is not about achieving carbonation at the end of fermentation. You'll also probably find out that with homebrewing equipment at ale temperatures you'll be limited by your equipment's capabilities so all you'll be able to do is set the maximum pressure your fermenter is rated for and accept that the beer will only be partly carbonated and will need some degree of force carbonation. The exception being if you're actually fermenting in kegs which are rated for much higher pressures than homebrew unitanks.

 

[jonbrout]

Thanks everyone for your thoughts. I will be fermenting under pressure, cold crashing and serving from the same keg.

 

[Off Balance Brewing]

I spund the end of my fermentation based on volume of co2 I want and the temp of the fermenter. Brewfather has a force carb calculator that lets you put in temp and volumes of co2, then I set my gauge to that recommended pressure. I cold crash after it's done fermenting and is mostly carbed. I don't ferment initially at that pressure though.

 

[DuncB]

I think that the Dr Hans calculator takes into account the gas laws.

As the gas ( and liquid below ) cools it's pressure will drop and equilibrium must be maintained. So put simply if at 22celsius and you want 2.6 vols you need 31.39 psi.
As the temp falls in gas the psi reduces and it equilibrates with the liquid ( the gas has less energy and less activity - pressure).
So it should be the same vols of gas at the cooler temperature as the gas that was more active now is less active and goes into the liquid, there is no more gas particles than before.
eg Take a bottle of coke off the shelf it is ideally carbonated when not open, you open it and gas rushes out to equalise with the air and also comes out of the liquid. If the bottle is much hotter this reaction is more violent and less if cooler.
The amount of gas in the bottle doesn't change with temperature as long as it's sealed as it's closed.
Same for your pressure fermenting.
Another example is suck back thru airlock when you cold crash all to do with equilibrium. No airlock and sealed container then it collapses!!
Hopefully someone with a physics qualification can clarify this better.

 

[SmallScaleOperator]

Ferment under your desired pressure, I do 1 bar. At the end of your fermentation pull off your spunding valve and put it at your regulator pressure for your serving CO2 volume. Chill and serve (your first several pints will probably be very cloudy and foamy). You may not hit your exact desired CO2 volume right away but you will be 90 percent of the way there.

 

[Qhrumphf]

If it's sealed and contains 2.4 volumes at 70F it'll contain 2.4 volumes at 40F. As it cools the pressure in the container will drop but the volumes of CO2 will not. Room temp pressure for normal levels beer carbonation is circa 30 PSI (depending on exact temp and carbonation level). Specifically 2.4 volumes at 70F should be 27.2 PSI.

I wouldn't do your whole fermentation at 27 PSI personally. I would do it much lower until the very end. If your sole goal is carbonation, then I wouldn't do the bulk of the fermentation under pressure at all (bar the negligible pressure to overcome the hydrostatic pressure of the airlock or blowoff liquid). As said, if that's your goal you're missing the point of pressure fermentation and perhaps overlooking the other impacts.

Rather, if carbonation is your only goal, do your fermentation with an airlock or blowoff like normal, and seal it only at the end. When you're about 4 points above your FG, that is when you'll put on your spunding valve set to 27 PSI. Worst case scenario if you spund it too late or finish higher than expected then you might need to supply a little more CO2 for the last bit of carbonation (as others have said, and for many unitanks including many commercial ones and almost all homebrew ones, 15 PSI or 1 bar max pressure ratings make this a requirement). If it finishes lower the spunding valve blows off the excess pressure.

 

[Vale71]

As you chill the beer more CO2 will be absorbed by it because of increased gas solubility. While the total amount of CO2 in the sealed vessel will stay the same its distribution between beer and headspace will change and possibly quite dramatically, depending on the headspace to beer ratio. With very little headspace, like in a bottle or a can, the change will be minuscule. With lots of headspace, like in a primary fermenter, the increase in carbonation can be significant.
For example with 20% headspace at a pressure of 2 bar and a carbonation level of 2.6 vols dropping temperature from 20°C to 0°C for cold crashing will result in a final carbonation level of 2.9 vols or a 0.3 vols increase. I leave quite a lot of headspace in my 14 gal Unitank and when I drop temperature to near freezing I have to reset the spunding valve a couple of times to prevent a significant increase in carbonation even though the beer was spunded at the correct pressure at the end of fermentation.

 

[Lurker]

Thanks everyone for your thoughts. I will be fermenting under pressure, cold crashing and serving from the same keg.

If your doing all this in a keg how are you dumping yeast / trub. Without a conical tank with a dump valve this isnt making sense to me?

 

[DuncB]

One way would be to use a floating dip tube in your ' fermenting keg' with a filter on it. Ferment under pressure using spunding etc and then when finished ( ie post cold crashing and + - condition) do a closed transfer to another ' serving keg'. Then all your trub etc will be in your brewing keg.
If you don't have a floating dip tube in your keg then I believe you would need to shorten the dip tube and probably still have a filter on it, but I haven't done this so not sure how well it works or can guide you as to the correct length. The floating dip tubes are cheap.

 

[Lurker]

Good idea and great point. I am all in on the Fermzilla all rounders! Cheap, clear, easy to clean, pressure rated...and did I say cheap!

 

[DuncB]

I agree, don't want to tie up the serving and dispensing kegs ( expensive ) with fermenting when such a good cheap and easier option available.
I'm using fermentasaurus for a few years now and happy with that. It's great to see what's going on!
Other option could be fermenter king junior from keg king, these are more keg sized, cheap and could be a ferment to glass solution as will fit in a kegerator. But you would be leaving the beer on the trub.

 

[Jim R]

I have a nice stainless fermenter but I use my Fermzilla All Rounder for pressure fermentation and really prefer it to the stainless one. As soon as I pitch the yeast, I put on my Spundit 2.0 spunding valve at 12 psi or so for fermentation. If my keg is empty, I fill it with Star San and purge it during fermentation by attaching a hose from the spunding valve to keg to take advantage of the free CO2. After fermentation I then do a pressure transfer to the purged keg (carefully with about a 1-2 psi pressure difference from the fermenter to the keg to avoid foaming), remove the spunding valve, place it in the refrigerator for cold crashing and attach my CO2 tank set to fine tune my desired carbonation level.

 

[SmallScaleOperator]

I have a nice stainless fermenter but I use my Fermzilla All Rounder for pressure fermentation and really prefer it to the stainless one. As soon as I pitch the yeast, I put on my Spundit 2.0 spunding valve at 12 psi or so for fermentation. If my keg is empty, I fill it with Star San and purge it during fermentation by attaching a hose from the spunding valve to keg to take advantage of the free CO2. After fermentation I then do a pressure transfer to the purged keg (carefully with about a 1-2 psi pressure difference from the fermenter to the keg to avoid foaming), remove the spunding valve, place it in the refrigerator for cold crashing and attach my CO2 tank set to fine tune my desired carbonation level.

I really like the look and price point of the all rounder. I may have to pick one up and try it out.

 

[North_of_60]

Thanks everyone for your thoughts. I will be fermenting under pressure, cold crashing and serving from the same keg.

I have pressure fermented two beers and I do what you are proposing. I use a floating dip tube. Both beers turned out great. I plan on doing it again.

I fill my keg and set the spunding valve to 15 psi, it stays at room temperature (68-72 degrees). The pressure keeps the krausen from blowing out the valve even with a full keg. After 7 days I put the keg in the kegerator at 25 psi and turn it down to 12 psi after 24 hours. By the time it’s cold crashed and down to serving temperature it’s drinkable but not fully carbonated. It takes about a week to be full carbonated.

I wanted to have the beer fully carbonated at the end of fermentation too, but I was afraid that 27.5 psi will affect the yeast like fermenting too cold. I have no science to prove this, it’s just what I have gathered from reading. I may be wrong. If you try fermenting at 27.5 let us know how it turns out.

There is an article somewhere on the web where an experiment was done using the same recipe at three different pressures. They concluded that somewhere around 15 psi was the sweet spot. I’ll see if I can find it again.

Found it: Pressure Fermentation with Chris White, John Blichmann- BeerSmith Podcast #163

Al

 

[DuncB]

I suppose the concern about affecting " the yeast like fermenting too cold " mentioned above depends on what you want or don't want from the yeast.
If warm fermenting ' a lager ' suppression of the esters would be a good thing. I replaced the barbed gas connector for a non return connector with MFL ( thought it was better but hadn't thought) on my spunding valve and set it to 15 psi on one brew. Returned three days later and the fermentasaurus was rigid at 35 psi on a wheat beer, I released the pressure gradually over several hours to prevent a fountain and continued at 15 psi for the next few days of the ferment and then turned it up. Yeast was going great guns even under that duress, beer came out ok but not as many esters as I wanted. Possibly due to the high pressure ? I tend to turn up the pressure on the spunding once the krausen has fallen and that helps it to be carbed by the end of ferment and after the diacetyl rest.

 

[SmallScaleOperator]

I suppose the concern about affecting " the yeast like fermenting too cold " mentioned above depends on what you want or don't want from the yeast.
If warm fermenting ' a lager ' suppression of the esters would be a good thing. I replaced the barbed gas connector for a non return connector with MFL ( thought it was better but hadn't thought) on my spunding valve and set it to 15 psi on one brew. Returned three days later and the fermentasaurus was rigid at 35 psi on a wheat beer, I released the pressure gradually over several hours to prevent a fountain and continued at 15 psi for the next few days of the ferment and then turned it up. Yeast was going great guns even under that duress, beer came out ok but not as many esters as I wanted. Possibly due to the high pressure ? I tend to turn up the pressure on the spunding once the krausen has fallen and that helps it to be carbed by the end of ferment and after the diacetyl rest.

I do all my lagers at 15 psi to reduce ester production and promote a clear crisp end product. When I do ales, I normally do them at normal atmospheric pressure, or maybe at 5 psi depending on what I am looking for as far as style and flavor. This is all at a normal cellar temp of 65 to 70 degrees F.
Last spring I tried a brewing a California Common using US0-5 at 15 psi. It came out so clean it tasted like a traditional lager. There is a lot of tinkering you can do using pressure and different yeast strains. I actually have not come across a yeast yet that did not ferment to full attenuation at 15 psi. That spunding valve has turned out to be a very cheep and useful tool.

 

[jackbflyin]

 

[jackbflyin]

[QUOTE="jackbflyin, po
[/QUOTE]
i think it was 10 psi needed approximately 1 week to carbonate 2.4 vol according to Brewfather app.