Perfecting nitro pours - any tips?

[lautzki]

Hi all!

I recently acquired some beer gas and a nitrogen regulator and decided to serve my Irish dry stout on nitro. I’ve pulled a few pints and the results are somewhat satisfactory, but we all know that this is not acceptable for us homebrewers

• I’m using a 70/30 N2+CO2 blend
• My serving pressure is at 31 psi / 2.1 bar and the beer is served at around 6c / 43f (this is also the pressure I force carbed the beer to 1.2 vols with)
• I’m using a 0.5 aerator disc in the stout spout with 5 holes in it
• My beer line length is around 2 meters
• It takes around 12 seconds to pull the first part of the two-part pour (using a Guinness gravity pint)

I’ve ran these figures through the EasyBlend app and they add up quite nicely.
The problem is that the cascade is fairly short (less than 60 seconds) and the head forms relatively quickly. Furthermore, the bubbles are fairly large, certainly not something you would expect from a nitro stout:

Any idea where to start troubleshooting this? For what its worth, the FG of the stout is 1.016 (around 4.5% ABV).

 

[DuncB]

I don't think you need such a long beer line. With a stout pour and a stout spout the restriction occurs at the tap. My line length is about one metre of 4mm internal evabarrier with the keg mid point about one metre below the tap.
Do make sure you fully turn tap on when you pour plenty of online videos showing the pour process.
You are at the lower end of the pressure for guinness.

 

[day_trippr]

Looking at the pertinent figures above it all seems like it should lead to success - indeed I could have written them all myself.

I carbonate to 1.2 volumes, have a Taprite faucet with a 5 x .5mm restrictor plate, use 6.5 feet of EVABarrier 4mm ID line (the minimum that will reach from keg to shank), and set my 70/30 beer gas to 35 psi. I do keep the keg colder at 36°F set point.

The CO2 provides the cascade, so my suspicion is the CO2 content is not actually 1.2 volumes but considerably lower. If there's an experiment to be conducted it might be to put the keg back on CO2 to bring the carbonation up then go back on the beer gas and see what happens. It shouldn't take long on the CO2 to establish a positive trend, then you can adjust as desired...

Cheers!

 

[lautzki]

I don't think you need such a long beer line. With a stout pour and a stout spout the restriction occurs at the tap. My line length is about one metre of 4mm internal evabarrier with the keg mid point about one metre below the tap.
Do make sure you fully turn tap on when you pour plenty of online videos showing the pour process.
You are at the lower end of the pressure for guinness.

Should I rather experiment with different restrictor plates than with beer line lengths to get the flow rate I want? My tap doesn't have flow control. Doesn't the size of the restrictor plate dictate how the head will form?

 

[lautzki]

Looking at the pertinent figures above it all seems like it should lead to success - indeed I could have written them all myself.

I carbonate to 1.2 volumes, have a Taprite faucet with a 5 x .5mm restrictor plate, use 6.5 feet of EVABarrier 4mm ID line (the minimum that will reach from keg to shank), and set my 70/30 beer gas to 35 psi. I do keep the keg colder at 36°F set point.

The CO2 provides the cascade, so my suspicion is the CO2 content is not actually 1.2 volumes but considerably lower. If there's an experiment to be conducted it might be to put the keg back on CO2 to bring the carbonation up then go back on the beer gas and see what happens. It shouldn't take long on the CO2 to establish a positive trend, then you can adjust as desired...

Cheers!

Someone actually suggested I might be a tad overcarbed, given the head looks like that. I'd say it's unlikely, as I force "carbed" the stout using the beer gas itself at serving pressure and temperature.

I'll try decarbing it and just leaving it for beer gas after that for a few weeks and see if it solves the issue.

 

[DuncB]

I find if the beer has too much CO2 in it that i basically pour foam with a stout spout. So quite the opposite of your issue. I'm erring towards @day_trippr theory of slightly too low CO2 in your beer.
Force carbing with beer gas at 31 psi I think would be a slow process. Usually you'd force carb with CO2 at 30 to 40 psi gauge pressure and you only have about 9 psi of gauge pressure for CO2.
I think?
@doug293cz may well put a red pen through my theory of gas laws!

 

[doug293cz]

I find if the beer has too much CO2 in it that i basically pour foam with a stout spout. So quite the opposite of your issue. I'm erring towards @day_trippr theory of slightly too low CO2 in your beer.
Force carbing with beer gas at 31 psi I think would be a slow process. Usually you'd force carb with CO2 at 30 to 40 psi gauge pressure and you only have about 9 psi of gauge pressure for CO2.
I think?
@doug293cz may well put a red pen through my theory of gas laws!

Here comes the red pen: With 70/30 beer gas @ 31 psig, the CO2 partial pressure is: (31+14.7) * 0.3 = 13.7 psia or -1.0 psig. OP is correct that their conditions work out to 1.2 volumes of CO2 at equilibrium.

Brew on

 

[doug293cz]

Someone actually suggested I might be a tad overcarbed, given the head looks like that. I'd say it's unlikely, as I force "carbed" the stout using the beer gas itself at serving pressure and temperature.

I'll try decarbing it and just leaving it for beer gas after that for a few weeks and see if it solves the issue.

Can you provide details of exactly how you force carbed, starting with filling the keg. Don't leave out anything.

Brew on

 

[day_trippr]

OP is correct that their conditions work out to 1.2 volumes of CO2 at equilibrium.

And I've been using that combination for years with success
But "equilibrium" is the key in this case I think.
The OP carb'd the stout prior to putting it on beer gas, and I suspect it hadn't reach equilibrium.

There is one other difference between the OP's beer and mine that I don't think matters but I'll mention it anyway: my stout starts at 1.106-7 OG and finishes around 1.023. That's a fair bit heavier in the FG department (and the ABV department, but again, probably doesn't matter) than the OP's 16 point FG...

Cheers!

 

[doug293cz]

And I've been using that combination for years with success
But "equilibrium" is the key in this case I think.
The OP carb'd the stout prior to putting it on beer gas, and I suspect it hadn't reach equilibrium.

There is one other difference between the OP's beer and mine that I don't think matters but I'll mention it anyway: my stout starts at 1.106-7 OG and finishes around 1.023. That's a fair bit heavier in the FG department (and the ABV department, but again, probably doesn't matter) than the OP's 16 point FG...

Cheers!

That's just it, I'm not sure OP carbed prior to putting on beer gas:

My serving pressure is at 31 psi / 2.1 bar and the beer is served at around 6c / 43f (this is also the pressure I force carbed the beer to 1.2 vols with)

Does that mean they "carbed" it on beer gas at 31 psi & 43°F, or carbed it with pure CO2 at 31 psi & 43°F. If the former, it's not carbed to 1.2 volumes. If the later, then it's probably carbed much higher than 1.2 volumes. That's why I asked for detailed information on their process.

The proper process is to carb to 1.2 volumes with pure CO2 (say at 6 psi and 67°F), and then put on beer gas and chill. Trying to carb on beer gas alone doesn't work very well because you deplete the CO2 in the headspace, and the gas that backfills the absorbed CO2 is only 30% CO2, so the partial pressure of CO2 in the headspace isn't enough to get to the desired volumes.

Brew on

 

[day_trippr]

I interpreted that to mean carbonation on straight CO2 - which is what I do, and indeed, I do it at "cellar temperature" because you can't practically carbonate a beer that low at fridge temps without some exotic regulator.

Anyway, I could be wrong, which would confirm the CO2 content was/is not up to snuff...

Cheers!

 

[DuncB]

I was thinking that the " force carbing " was done with beer gas at 31 psi hence my disordered physics but gut feeling the carbonation was too low because of this incorrect process.

 

[day_trippr]

Upon further review, I'm now inclined to agree with you two gentlemen that the OP used beer gas to carbonate his stout.
With all the frailties therefrom...

Cheers!

 

[lautzki]

Yes, you are correct. I thought I could shake the keg whilst it's hooked to beer gas to encourage getting the CO2 into solution and thus avoiding potential overcarbonation if it's in serving temp and pressure. I feel a bit stupid now!

So should I take it to room temp and carbonate it to 1.2 vols using CO2?

 

[doug293cz]

Yes, you are correct. I thought I could shake the keg whilst it's hooked to beer gas to encourage getting the CO2 into solution and thus avoiding potential overcarbonation if it's in serving temp and pressure. I feel a bit stupid now!

So should I take it to room temp and carbonate it to 1.2 vols using CO2?

You shouldn't feel stupid. It's difficult to get all of the nuances of gas laws correct. I write a lot about them on HBT trying to help others understand how the physics work in real life.

Yes. Warming to room temp and then carbonating with pure CO2 would be the first thing to try. At this point I would avoid trying to accelerate carbonation by using higher than equilibrium (chart) pressure, but agitation at equilibrium pressure carries no risk of over-carbonation.

Brew on

 

[day_trippr]

You can use chart pressure and safely accelerate the carbonation process by agitation. I tilt the standing keg back and forth about 20° until I can't hear gas entering the keg, let the keg sit for an hour or two, then do another rocking cycle.

Repeat a few times and you can get a keg close to fully carbonated in an afternoon with no risk of over carbonation...

Cheers!

 

[lautzki]

Ok, before trying to carb it with pure CO2, I decarbed the beer and tried to bump up the beer gas pressure to 35 psi (keg at 5c) and shake the keg just to see how it behaves, just for science, because.. you know.. I still find it puzzling that the head would behave like that like it did if the beer was undercarbed - getting a large head full of CO2-like bubbles with a short cascade.

After letting it sit for a few hours, I pulled a pint and the cascade was super long and it left a VERY large head that was full of tiny fish-eye bubbles.

Could it be that the beer gas mix is actually not 70/30, but the CO2 level is much higher? Am I missing something here? FWIW, I got the beer gas as a custom mix from my local weld shop and the cylinder pressure is 200 bar. I believe it has a siphon/dip tube/mixing tube/blending tube or whatever. If my room temp is at 21c/70f, wouldn't that mean the CO2 is in liquid state?

I've obviously pulled a few pints now, and I was wondering whether the extra headspace is the cause for it to overcarbonate when agitated.

You might want to check this video out where a guy pulls a perfect pint after shaking the keg on beer gas:

My head is not even remotely as tight and creamy as there, and it dies down into these fish-eye bubbles that resemble more something on a beer that's carbed normally with CO2.

 

[lautzki]

Here are some pints I pulled 24 hours after shaking the keg at 35psi/5c (with BEER GAS!) and reducing the serving pressure to 30 psi. If this is not overcarbonation I don’t know what is. How can it be if it's impossible to overcarb with beer gas at serving temp and pressure? Please, @doug293cz , slap some sense in me.

 

[beren]

Try letting out the pressure, shake the keg, and try again at 20-25psi

 

[Broken Crow]

In light of your more recent thread; Is the beer gas ratio measured by volume or by mass? I'm left to ask if you ever bothered to follow the above advice to warm it up and carbonate with pure CO2?
Starting another thread questioning a potential gas mix problem made me look back here and wonder if you solved the initial issue at all, (which is left unstated in the new thread) and if so; How did it go? Are you still having the same problem?

 

[lautzki]

Yes, the beer was carbonated with pure CO2 to 1.2 volumes. The results were fine initially, but hooking it to my beer gas cylinder overcarbed the keg over time.

 

[doug293cz]

Yes, the beer was carbonated with pure CO2 to 1.2 volumes. The results were fine initially, but hooking it to my beer gas cylinder overcarbed the keg over time.

That does sound like your CO2 ratio in the gas mix is too high.

Brew on

 

[pigroaster]

I carb my stout taps kegs at 7 psi CO2 and serve at 12-18 psi and get perfect pours at 38 F. To each their own! I get the cascade and it tastes great! Yes I use beer gas 70/30

 

[Broken Crow]

Most of the gas blenders in welding shops are perfectly adequate for welding, but outside of the extremely expensive units used by the large gas suppliers, they don't have the precision to do much better than +/-5% or higher. Do they supply local beer-serving venues? There has to be a local supplier of properly mixed beer gas...You could always find a bar that serves Guinness on tap and ask them where they get theirs.