How to prep/carbonate a beer before serving on Nitro

Discussion in 'Homebrewing' started by Finn, Dec 10, 2016.

  1. Finn

    Finn Initiate (0) Nov 20, 2003 Pennsylvania

    Hey folks, I've got just about all set up for pouring my stouts on Nitro (I have the regulator, stout faucet, and the beers are kegged). What is your protocol for prepping the beer before serving with the Nitro/CO2 blend? Can I just serve right away after I carbonate the stout (with straight CO2 to about 1.2 volumes) or do I need to acclimate the stout to the nitro gas blend for a week first as some suggest?

    Any info much appreciated
  2. DavidlovesCBC

    DavidlovesCBC Initiate (90) Jan 25, 2014 Florida

    I believe it's better to, after carb, let it condition for a week. Crank the beer gas to 30 psi and let it sit. I have also noticed that beer line plays a factor also. I have a keezer and 5ft of 3/16 beer line is good
    Finn likes this.
  3. billandsuz

    billandsuz Disciple (368) Sep 1, 2004 New York

    Since the nitrogen is inert and is not absorbed very much into the liquid you can treat the beer as you would any keg. with the exceptions you note.

    you may want to let the beer age for a week or a few weeks, mostly because all green beer benefits from some cold ripening. but it doesn't change the nitrogen, it still doesn't get absorbed into the beer.

    carbonation must be quite low, 1.2 vols. If you carbed this beer to typical 2.5-2.7 you will have a frothy mess.

    Use 75/25, aka G Gas, aka Guinness gas. If you ask for "Beer Gas" it might be 75/25, probably will be 75/25. Might be 80/20. One vendor around here sells 90/10. So specify 75/25.

    The N provides the pressure to force the beer through the disk in the faucet. 30 to 33 psi is required.

    Voila. There you have it.
    Finn likes this.
  4. PortLargo

    PortLargo Devotee (435) Oct 19, 2012 Florida

    You have a lot of variables going on here. You would like to hear something like XX psi for YY days, but there is some math involved. The goal is for the applied pressure (CO2) to achieve the desired carbonation level in your beer.

    First, you must know the ratios of your beer gas, typically 75/25 but you should confirm and this is vital. The CO2 input from the beer gas must be set to give the desired carb level of the beer. Here's how you compute that: Multiply the fractional percentage of the CO2 by the applied pressure, i.e. if you have 75/25 at 30psi that's the equivalent of .25 times 30, or 7.5psi (partial pressure of CO2). Enter your carbonation chart with this figure and the exact beer temp and you'll arrive at the carb level.

    You actually work the problem in the reverse of what I stated above. Enter the carb chart with your desired volumes and known temp to get the desired pressure, then divide this pressure by your fractional percentage of CO2 to get the beer gas pressure.

    Your 1.2 volumes seems low, even for a stout . . . that's not much more than the residual carbonation from fermentation. You are actually "off the chart" (40F @ 1 psi equals 1.47 volumes). Other sources of error: you must know beer temp, if off a couple of degrees then everything changes. You must know N2/CO2 ratios, if ask your supplier and there is a long pause before an answer then they probably don't know. If this ratio is off then you see how all the results are off. If you have any errors it will take days for the CO2 levels to equalize. No work around here, that's the nature of gas dissolving into a liquid. So a good pour today may be off next week (or vice versa). Once you reach equilibrium you're ready to serve, this could be after one minute or one month.
  5. billandsuz

    billandsuz Disciple (368) Sep 1, 2004 New York

    I am pretty sure Guinness is at 1.2 vols. That beer is flat as Kansas after 5 minutes in the glass.

    Personally, I think the keg should be charged with straight CO2 to get the carbonation desired, then switch it to the blend. Because Math. And blend gas is expensive.
    Finn and DavidlovesCBC like this.
  6. DavidlovesCBC

    DavidlovesCBC Initiate (90) Jan 25, 2014 Florida

    Yeah i agree. Carb with pure co2 and save your nickels. I have carbed to 1.8 with good results
  7. PortLargo

    PortLargo Devotee (435) Oct 19, 2012 Florida

    I defer to your experience and agree using straight CO2 initially is preferred. But 1.2v is really low, it's literally off the chart. Living in FL, I understand flat . . . but I wanted the OP to realize his target might be difficult.
  8. NeroFiddled

    NeroFiddled Poo-Bah (10,332) Jul 8, 2002 Pennsylvania
    Premium Trader

    Perhaps I'm confused. Is the idea here that you're pouring a 100% CO2 beer through a sparkler pushed by nitro/CO2 blend?

    Unless I'm even more confused, actual nitro beers are carbed with the nitro blend, thus the nitrogen breakout which creates the creamy head (because nitrogen is not as soluble as CO2 and thus comes out of solution readily).

    I know that many bars have run non-nitro beers with the mix, but that's not really the same.

    If you're just looking to 'sparkle' the beer I don't see any need really to even push with nitro. I'd like to know what everyone's thought are. Hopefully VikeMan will chime in.
    #8 NeroFiddled, Dec 11, 2016
    Last edited: Dec 11, 2016
  9. billandsuz

    billandsuz Disciple (368) Sep 1, 2004 New York

    Thanks for the nod.
    I don't brew nitro beer. That stuff is boring imo. People like it a lot though, and give the people what they want. I do believe that the novelty at a homebrew level would probably wear off quickly. And despite having a basement full of nitro gear, I never thought "Hey Bill, you should set up Nitro in the house".

    I never realized how undercarbed Guinness really is. I knew it was flat, but yeah, 1.2 vols is practically not carbonated at all. But they claim 1.2 vols. So be it.

    Finn likes this.
  10. Finn

    Finn Initiate (0) Nov 20, 2003 Pennsylvania

    Glad you guys brought all that up: I was having trouble seeing how 1.2 volumes was enough, but I read that in a couple brewing publication articles online and just trusted it...So you guys think more like 1.7 volumes would be better?
  11. Finn

    Finn Initiate (0) Nov 20, 2003 Pennsylvania

    Most sources I've read (professional brewers and homebrewers) say you can just carb with straight co2, then serve with the 75/25 nitro blend. The purpose of the nitro is to allow a higher serving PSI to push the beer through the restrictor plate holes in the stout faucet, which knocks the co2 out of solution, causing the cascading effect in the glass.....At least that's what most people have told me.
  12. Finn

    Finn Initiate (0) Nov 20, 2003 Pennsylvania

    I hear ya, I generally don't prefer nitro beer either, but the brewpub I used to work at served their stouts on nitro almost exclusively and were amazing. The best stouts I've ever had. Their recipes were part of that for sure, but I (and most others there) enjoyed them more through nitro.
  13. VikeMan

    VikeMan Meyvn (1,468) Jul 12, 2009 Pennsylvania

    I'm not a Nitro/Beer Gas expert by any means. But my understanding from what I have read in several places is that the main purpose of the nitrogen is to allow high pressure (to force beer through the restrictor plate) without raising the carbonation level, and that whatever nitrogen manages to dissolve or infuse into the beer itself may add some mouthfeel, but that this is a minor effect.

    That said, you can find quite a few brewery web pages out there touting their nitro beers and crediting nitrogen infusion with the mouthfeel. Whether that's willful exaggeration or ignorance, or whether the nitrogen itself contributes more than a lot of people think, I don't know.

    Someone should do an experiment with just CO2 and a restrictor plate setup... carbonate to a modest level, then raise the CO2 pressure just to push the beer through the restrictor plate. Would it look, feel, and taste just the same as if it had been served with a proper nitro/beer gas setup?
    billandsuz likes this.
  14. billandsuz

    billandsuz Disciple (368) Sep 1, 2004 New York

    I can tell you from experience that if a keg of beer that was intended for nitro inadvertently becomes charged with CO2, well, good luck. This is not unknown. We install a switch, on for G Gas, or off for straight CO2, and if someone screws up puts nitro beer on CO2 it is a mess. Gas beer on N will just go flat but N beer on 100% CO2 will pour like a beer mousse.

    Nitrogen is inert, that much is a fact. No taste,. No odor. Nothing. And about 100x less soluble than CO2. But CO2 gas does have flavor, and some bite. Remove CO2 and you lose some of that acidic bite on the nose.

    N pushes the beer through the restrictor plate. It does not really dissolve in liquid so it can add pressure without charging the liquid with gas. Apply 100% CO2 at 33 psi and the low vols beer will absorb CO2 like a sponge until the head pressure equilibrates with the liquid pressure,and then you are quickly at 10, 12 14? vols. Not good.

    One thing about beer gas is that it can move beer real quick. Because the vols are so low, just an hour on mix gas is enough. Try it with cold brew coffee. It is quite good!
  15. NeroFiddled

    NeroFiddled Poo-Bah (10,332) Jul 8, 2002 Pennsylvania
    Premium Trader

    OK, I got it. We're not talking about nitro beers, we're just replicating what a British beer engine does (which is what Guinness was doing when they invented the nitro pour).
  16. jespinet

    jespinet Initiate (0) Feb 12, 2018 North Carolina

    Hi! This is a great discussion and I really appreciate the information. I just brewed a dry Irish stout yesterday and have all the nitro gear. Based on what I am reading here, I think I have the information I need to get my beer carbonated and served. Here is my question - do I leave the 75/25 gas on the keg when I am not serving? Will the beer continue to carbonate from the CO2 that is in the mix if I leave the gas on the keg during storage in my keezer?
  17. VikeMan

    VikeMan Meyvn (1,468) Jul 12, 2009 Pennsylvania

    Assuming the beer was already carbonated, and the pressure you're using with the beer gas is set to maintain the same equilibrium CO2 level, it won't carbonate any further.
    Prep8611 likes this.