Nitro beer help needed!!

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Driddy

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I am currently prepping my first Nitro Stout. The system is set up with beer gas and regulator and what I believe to be the right length 3/16" beer line (8').

Specifically my question is the method to force carb the stout to 1 to 1-1/2 volumes of CO2. I'm just not getting the "science".

I typically force carb my CO2 beers by the "set it and forget it" method. Takes longer but seems to be less problematic than other methods. I'm not sure I can do that with the Nitro system. Hoping someone more knowledgeable in the nitro world can help me with this.

If you refer to traditional carbonation charts, to get the proper carbonation, the beer needs to be either too warm or pressure way too low for dispensing purposes. Combine that with the fact that you need to have the regulator at 25 psi or more to have a proper pour of the beverage. It doesn't add up.

I get that the beer gas (25/75 mix) is only part CO2. So if you presume that only 25% pressure is CO2 and is absorbed you would have a theoretical CO2 pressure of about 6 psi. Way more than what is required for the desired volumes of CO2 for the style. Eventually the beer would "over carb". (I'm assuming). So how do you avoid it?

As a additional thought. Do I even need to "force carb" the beer? If I understand the "science", the beer post fermentation, is already close to 1 volume anyways (if you go with what the formula results are in Pro Mash given the fermentation temp ect.).

So to clarify, can I "set it and forget it" and if so, at what pressure and temp? Keeping in mind that I will want it on the cooler side, not the traditional "cellar" temp.

Thanks for your patience with my lengthy question and for your insightful responses.

Best Regards,

Driddy
 
Man...everybody seems to be getting nitro lately, and I'm just here debating...

To answer though, it seems like most recommendations state to force carb using pure CO2 using the chart and time. Then move over to your nitro system and run it at serving pressure. Seems like many folks recommend leaving that on for a week or so before dispensing as well, but I've heard varying accounts.
 
Man...everybody seems to be getting nitro lately, and I'm just here debating...

To answer though, it seems like most recommendations state to force carb using pure CO2 using the chart and time. Then move over to your nitro system and run it at serving pressure. Seems like many folks recommend leaving that on for a week or so before dispensing as well, but I've heard varying accounts.

I don't really understand why you leave it on nitro after you've carbonated it but before you serve it. I thought that very little nitrogen dissolves in the beer, so why do it?
 
I don't really understand why you leave it on nitro after you've carbonated it but before you serve it. I thought that very little nitrogen dissolves in the beer, so why do it?

Honestly, I'm unsure as well, just going off the recommendations I've heard.
 
I've seen the recommendations regarding carbing with pure CO2 then dispensing with nitro mix. The problem is the charts would have me set the pressure at -5.4 Deg F.(that's a negative!) or a temperature that's too high...in the 60 Deg F range. So even if I did carb at 60 Deg, to get the 1 volume recommended, once on the beer gas at the recommended 25-30 psi, would it not eventually over carb due to the 25% co2? 30psi x 25% = a relative 7.5 psi. At a serving temp of 50 deg F it would eventually carb to a level higher than what's wanted.
 
I haven't found an exact science for carbing with CO2 and then switching to nitro but I just leave it on for a week at 7-8lbs and then switch it over. Never felt over-carbed.

As far as time lapse after switching to nitro, the way I see it (opinion only) is that the nitro has to have time to "penetrate" the beer. It does not dissolve as CO2 will, bu remember the nitro is entering from the top of the keg and has to make its way ultimately to the bottom to be picked up. The head pressure is higher for sure, but you don't instantly have beer that is at nitro equilibrium.
 
...

If you refer to traditional carbonation charts, to get the proper carbonation, the beer needs to be either too warm or pressure way too low for dispensing purposes. Combine that with the fact that you need to have the regulator at 25 psi or more to have a proper pour of the beverage. It doesn't add up.

I get that the beer gas (25/75 mix) is only part CO2. So if you presume that only 25% pressure is CO2 and is absorbed you would have a theoretical CO2 pressure of about 6 psi. Way more than what is required for the desired volumes of CO2 for the style. Eventually the beer would "over carb". (I'm assuming). So how do you avoid it?

As a additional thought. Do I even need to "force carb" the beer? If I understand the "science", the beer post fermentation, is already close to 1 volume anyways (if you go with what the formula results are in Pro Mash given the fermentation temp ect.).

...

Driddy

I've seen the recommendations regarding carbing with pure CO2 then dispensing with nitro mix. The problem is the charts would have me set the pressure at -5.4 Deg F.(that's a negative!) or a temperature that's too high...in the 60 Deg F range. So even if I did carb at 60 Deg, to get the 1 volume recommended, once on the beer gas at the recommended 25-30 psi, would it not eventually over carb due to the 25% co2? 30psi x 25% = a relative 7.5 psi. At a serving temp of 50 deg F it would eventually carb to a level higher than what's wanted.

You're kind of on the right track as far as the CO2 component of the pressure being only 25% of the total pressure. What you're missing is that when working with partial pressures (the proper term for the contribution to total pressure of a single gas in a mixture) you have to use absolute pressures, not gauge pressures. Absolute pressure equals gauge pressure plus local atmospheric pressure (14.7 psi at sea level.) So, if your gauge pressure is 12 psi, the absolute pressure is 26.7 psi. If the headspace is 100% CO2, then the CO2 partial pressure is 26.7 psi. If the headspace is 25% CO2 and 75% N2, then the CO2 partial pressure is 26.7 * 0.25 = 6.675 psi, and the N2 partial pressure is 26.7 * 0.75 = 20.025 psi.

Carbonation levels are actually determined by CO2 partial pressure (and temp), not gauge pressure. The carbonation charts include a conversion from absolute pressure to gauge pressure, since that's all you can really measure (unless you have expensive gauges.) When using the charts with beer gas, you need to convert the gauge pressure on the chart back to absolute pressure, and use that in all of your calculations.

25/75 beer gas at 25 psig has an absolute pressure of 39.7 psia, and a CO2 partial pressure of 39.7 * 0.25 = 9.925 psi. In terms of gauge pressure this would be 9.925 - 14.7 = -4.775 psi.

If you want to fully carbonate with CO2 prior to putting on beer gas, you have to do it at higher than serving temperature, as there is no way to get negative gauge pressures on our systems. If you don't want to do that, then you just have to put it on beer gas at serving temp and pressure. It will be a little undercarbed initially, but lots of brewers do it this way and find it acceptable.

Brew on :mug:
 
Ahhhh....there's the missing component!! Atmospheric Pressure! Should have been obvious that when my pressure gauge is reading 0 there is still 14.7 psi on he liquid! Classic example of "not seeing the forest for the trees"!

Doug293cz, Thanks for you input and knowledge.

I will just put it on the beer gas and call it good.
 
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