Fermentation

[Brewer #355043]

Would like to know if co2 is absorb into the beer. I have a brew in the fermenter at present and is under pressure. I had my spunding valve set at 14psi and temp at 18 degrees celsius. I know anything over 14psi will be released. As we are now in day 4 the valve is reading 0. I am using a keg king junior fermenter with a blow tie combination spunding valve.As the initial fermentation has stopped would the co2 less than 14psi be absorb into the beer which is why i have 0. There must still be some pressure in there as i can not press the sides in.

 

[GFHomebrew]

Would like to know if co2 is absorb into the beer. I have a brew in the fermenter at present and is under pressure. I had my spunding valve set at 14psi and temp at 18 degrees celsius. I know anything over 14psi will be released. As we are now in day 4 the valve is reading 0. I am using a keg king junior fermenter with a blow tie combination spunding valve.As the initial fermentation has stopped would the co2 less than 14psi be absorb into the beer which is why i have 0. There must still be some pressure in there as i can not press the sides in.

Yeah for sure there is a carb chart that gives temp and preassure to find how carbonated the beer will be.
https://cdn.shopify.com/s/files/1/0152/1071/files/Forced_Carbonation_Chart.jpg?589861227676789557
There's one.

 

[Nosybear]

Would like to know if co2 is absorb into the beer. I have a brew in the fermenter at present and is under pressure. I had my spunding valve set at 14psi and temp at 18 degrees celsius. I know anything over 14psi will be released. As we are now in day 4 the valve is reading 0. I am using a keg king junior fermenter with a blow tie combination spunding valve.As the initial fermentation has stopped would the co2 less than 14psi be absorb into the beer which is why i have 0. There must still be some pressure in there as i can not press the sides in.

Chilled, that will be a fairly flat beer. At 18 C, I'd think you would want closer to 35 psi to get the carbonation you want at serving temp. Get and use a carbonation chart to tell you where to set the spunding valve.

 

[Donoroto]

would the co2 less than 14psi be absorb into the beer which is why i have 0.

No. The gas pressure in the liquid and in the 'air' will always be the same after a time.

If there was CO2 in the liquid, but not in the 'air', it would fizz out - this is called 'going flat'. Leave a beer (or soda) in a glass for a day or two to witness this phenomenon.

 

[HighVoltageMan!]

As you cool the beer the pressure will drop because the co2 is being absorbed into the liquid (going into solution). If you raise the temperature the pressure will rise because the co2 is coming out of the liquid (coming out of solution). Temperature affects this coming and going in and out of solution. The colder the temperature, the more co2 will go into solution and the the pressure drops. Warm it up and the opposite happens. If the temperature stays the same, the gas and liquid will equalize and the the pressure will stabilize, unless you have a leak. Then you will see zero pressure.

I ferment about 2/3 of my beer under pressure. 14 PSI at 18C (64F) will be low on carbonation, but not flat. About 25-30 PSI at 18C will give you @ 2.5 volumes or so.

 

[Donoroto]

If the temperature stays the same, the gas and liquid will equalize and the the pressure will stabilize, unless you have a leak. Then you will see zero pressure

I dispute that. Zero pressure on the gas side (above 32 F) implies zero* dissolved gas.

Or did I misinterpret? After a leak you'd see zero (which I agree with).

*Almost. Atmospheric pressure is 14.7 psi, which contributes some but almost none.

 

[HighVoltageMan!]

I dispute that. Zero pressure on the gas side (above 32 F) implies zero* dissolved gas.

Or did I misinterpret? After a leak you'd see zero (which I agree with).

*Almost. Atmospheric pressure is 14.7 psi, which contributes some but almost none.

What I meant by that is if the beer was fermented at 14PSI and finished, the pressure would remain relatively stable. If it drops to zero afterward, it’s likely a leak in the system somewhere, which can happen easily.

 

[Donoroto]

What I meant by that is if the beer was fermented at 14PSI and finished, the pressure would remain relatively stable. If it drops to zero afterward, it’s likely a leak in the system somewhere, which can happen easily.

Ah, yes, my second interpretation was accurate. In that case, no dispute at all @HighVoltageMan! We are on the same page here.

Speaking of leaks, pressurized the keg of hefeweitzen to 30 psi. Sample at 24 hours was... flat. Gas post somehow became loose, despite it holding pressure for weeks with sanitizer in the keg. Tightened it, all is well.

 

[J A]

If you have a spunding or pressure relief valve set for 14 PSI and no negative temperature change and no leaks, your gauge should be showing 14 PSI. If the temp didn't change, you probably have a leak.
If the system is intact and CO2 can't get out then as temp drops pressure drops as a function of the expansion and contraction of CO2 with temperature. Pressure changes with temp, not the volume of CO2. To increase volume of CO2 in suspension you have to increase pressure as the temp lowers.
When I use my Unitank, I close everything off with several points left in the fermentation, usually at around 68 degrees. As fermentation finishes, the pressure maxes out at the PRV setting - around 20 lbs. At that pressure and temp, the beer doesn't have enough volumes of CO2 in suspension, but it's somewhat carbonated. It stays that way until I start dropping temp and I have to top up with CO2 to maintain and increase the level of carbonation as temperature lowers.