Question about Co2 and fermenting under pressure

Discussion in 'Beginners Brewing Forum' started by KenBrew, Aug 9, 2020.

  1. KenBrew

    KenBrew New Member

    Joined:
    Aug 9, 2020
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    1
    Hey there!

    My question is basic, how much CO2 does a beer fermented under pressure at 5 PSI at 68 degrees Fahrenheit produce? Does the fact that it is under pressure increases the residual level of carbon dioxide?

    Thanks !
     
  2. thunderwagn

    thunderwagn Well-Known Member

    Joined:
    Sep 5, 2015
    Messages:
    3,750
    Likes Received:
    7,305
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Loveland, CO
    I'd say 1 vol or a bit less even. If you're looking for a good place to start with, I'd recommend setting your spunding valve at 12 psi. I'm over 5000ft above sea level and have mine set at 15. My beer is almost perfectly carbonated once fermentation is done.
    You won't be increasing the residual level just because you're fermenting under pressure. You are still, or should be releasing pressure in excess of what you have your spunding pressure set to. Hope that makes sense or helps.
     
  3. KenBrew

    KenBrew New Member

    Joined:
    Aug 9, 2020
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    1
    The idea is to obtain the co2 level through the conditioning in the bottle. So I want to do the calculation of the amount of OZ of corn sugar .. thanks, what I really wanted to know was that if fermentation under pressure increases the residual level of carbon dioxide .. thanks!
     
  4. Hawkbox

    Hawkbox Well-Known Member

    Joined:
    Jul 27, 2017
    Messages:
    3,756
    Likes Received:
    2,983
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    IT Manager
    Location:
    Edmonton
    It will increase CO2 cause that is what causes the pressure. The math is figuring out how much.
     
    Pricelessbrewing likes this.
  5. thunderwagn

    thunderwagn Well-Known Member

    Joined:
    Sep 5, 2015
    Messages:
    3,750
    Likes Received:
    7,305
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Loveland, CO
    How do you plan on bottling? I ask because your normal method of transferring beer to a bottling bucket and using a bottle filler wand is not going to work if you've fermented under pressure. As soon as you release the pressure from the vessel, you've got a foam volcano coming. You could transfer to keg under pressure and assuming your beer is properly carbonated, you can use a beer gun to bottle.
    I don't think what you're looking to do is going to work, if your plan is to carb under pressure to a certain level and then add sugar to get to the finishing level of carbonation.
     
  6. Nosybear

    Nosybear Well-Known Member

    Joined:
    Jul 16, 2012
    Messages:
    9,418
    Likes Received:
    6,670
    Trophy Points:
    113
    Location:
    Aurora, CO, USA
    The same amount as fermentation at normal pressure. Every 342g of maltose (1 mole) produces 176g of carbon dioxide (4 moles). The residual CO2 is dependent on pressure but I don't have that table handy.
     
    Pricelessbrewing likes this.
  7. KenBrew

    KenBrew New Member

    Joined:
    Aug 9, 2020
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    1
    That is correct, it's exactly what I want to do.. I just wanted to know the residual level of carbon dioxide after fermentation so I don't overprime the beer before bottling...
     
  8. thunderwagn

    thunderwagn Well-Known Member

    Joined:
    Sep 5, 2015
    Messages:
    3,750
    Likes Received:
    7,305
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Loveland, CO
    Best advice I can give is that if you want to add sugar and bottle, skip fermenting under pressure, and just use a blow off tube. Unless you can fully carb and use a beer gun like I mentioned above, you're going to have a mess on your hands.
     
  9. Hawkbox

    Hawkbox Well-Known Member

    Joined:
    Jul 27, 2017
    Messages:
    3,756
    Likes Received:
    2,983
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    IT Manager
    Location:
    Edmonton
    Yeah if you're planning to bottle anyway there is no value in trying to pressure ferment as well.
     
    thunderwagn likes this.
  10. Craigerrr

    Craigerrr Well-Known Member

    Joined:
    Mar 14, 2018
    Messages:
    4,701
    Likes Received:
    6,904
    Trophy Points:
    113
    The mess Thunderwagon is referring to is exploding bottles, not just messy, but very dangerous.
     

Share This Page

arrow_white