Stout nitro tap help

[Closet Fermenter]

I’ve been dispensing my stout with just CO2. But, after picking up a couple extra tanks, I decided to give beer gas a try. I got a 75/25 mix last week and hooked it up to my keg, and set the regulator to 8 psi. I was dispensing with a picnic tap on 5.5’ of eva barrier line put together with duotight connectors. No problems.
Today, my Micromatic stout tap arrived, so I swapped out the party tap with the stout faucet using a duotight beernut connection. I get a full glass of foam.
What am I doing wrong here?

 

[day_trippr]

Inside that stout faucet is a round disk with five tiny holes through it. With the gas pressure set to the recommended 30-35 PSI, those tiny holes are intended to knock CO2 out of suspension and provide that cascade that a good stout pour is known for.

But, the beer cannot be carbonated above around 1.4 volumes of CO2. Otherwise you get that foam fest. So, I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 using "chart pressure" and the pours are lovely with the beer gas pressure at 35 psi, especially in a classic nonic glass. And I used a Micromatic stout faucet for well over a decade but eventually switched to a Taprite (that's actually made by Krome Dispense) this winter. But they both pour nicely at 35 psi...

Cheers!

 

[Closet Fermenter]

Inside that stout faucet is a round disk with five tiny holes through it. With the gas pressure set to the recommended 30-35 PSI, those tiny holes are intended to knock CO2 out of suspension and provide that cascade that a good stout pour is known for.

But, the beer cannot be carbonated above around 1.4 volumes of CO2. Otherwise you get that foam fest. So, I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 using "chart pressure" and the pours are lovely with the beer gas pressure at 35 psi, especially in a classic nonic glass. And I used a Micromatic stout faucet for well over a decade but eventually switched to a Taprite (that's actually made by Krome Dispense) this winter. But they both pour nicely at 35 psi...

Cheers!

Thank you so much. I’m probably a little bit high, as I have been shooting for around 1.5 volumes.
One follow up; is there anything specific I should do about the length of the beer line, or does that not come into play here?

 

[day_trippr]

Beer line length really doesn't matter much with a stout faucet as the restrictor plate dominates. I run just enough line on my stout faucet to reach the keg from the tower mounted faucet...

Cheers!

 

[Closet Fermenter]

Inside that stout faucet is a round disk with five tiny holes through it. With the gas pressure set to the recommended 30-35 PSI, those tiny holes are intended to knock CO2 out of suspension and provide that cascade that a good stout pour is known for.

But, the beer cannot be carbonated above around 1.4 volumes of CO2. Otherwise you get that foam fest. So, I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 using "chart pressure" and the pours are lovely with the beer gas pressure at 35 psi, especially in a classic nonic glass. And I used a Micromatic stout faucet for well over a decade but eventually switched to a Taprite (that's actually made by Krome Dispense) this winter. But they both pour nicely at 35 psi...

Cheer

Inside that stout faucet is a round disk with five tiny holes through it. With the gas pressure set to the recommended 30-35 PSI, those tiny holes are intended to knock CO2 out of suspension and provide that cascade that a good stout pour is known for.

But, the beer cannot be carbonated above around 1.4 volumes of CO2. Otherwise you get that foam fest. So, I carbonate my imperial chocolate stout to just 1.2 volumes of CO2 using "chart pressure" and the pours are lovely with the beer gas pressure at 35 psi, especially in a classic nonic glass. And I used a Micromatic stout faucet for well over a decade but eventually switched to a Taprite (that's actually made by Krome Dispense) this winter. But they both pour nicely at 35 psi...

Cheers!

Well, here I am again. I made a new batch and force carbed at a controlled 70°F and just under 8psi; shooting for a carbonation of 1.2 volumes.
I chilled my keg down to 40° and hooked up the beer gas set at 35 psi. I still get a full glass of foam! No doubt, it’s nice, creamy foam, and it does settle out after a few minutes, but it takes me three pours to feel like I have had a single beer.

 

[day_trippr]

According to the Brewer's Friend carbonation calculator 70°F and 7.9 psi does indeed work out to 1.2 volumes.

But the one thing neither our favorite carbonation table or this calculator consider is how much CO2 was already in the beer before the exogenous gas is added. I suppose it's possible your stout was on the high end of the expected residual carbonation from fermentation. Taking the keg out of your kegerator/keezer and venting it might be necessary...

Cheers!

 

[Bobby_M]

It's hard to know why, but while you pour, look closely at the tubing between the keg and shank. Is it solid beer or is there obvious foaming in the line itself? If there are bubbles in the line, beer gas is injecting into the beer path in the keg somewhere.

 

[day_trippr]

Absolutely true, which I confirmed once again just a week or so ago. In my case there was a very small slice in the Out dip tube O-ring that was allowing enough CO2 to be injected into the beer stream under the Out post to act like a creamer pour. I immediately checked the line leaving the keg and there was foam all the way to the QD. Changed out that O-ring and all was right again...

Cheers!

 

[Closet Fermenter]

Thanks! This all makes sense. I’ll definitely try to track this down and let you know what I find.

 

[Closet Fermenter]

According to the Brewer's Friend carbonation calculator 70°F and 7.9 psi does indeed work out to 1.2 volumes.

View attachment 861817

But the one thing neither our favorite carbonation table or this calculator consider is how much CO2 was already in the beer before the exogenous gas is added. I suppose it's possible your stout was on the high end of the expected residual carbonation from fermentation. Taking the keg out of your kegerator/keezer and venting it might be necessary...

Cheers!

I’m sitting here thinking about this and wondering just how much carbonation could possibly be in the beer after fermentation. I didn’t do any pressure fermenting, so how much carbonation is possible.
The main thing that puzzles me is that the understanding that I have of gases, (poor at best), tells me that the forced carbonation is an equilibrium process, and not necessarily a cumulative or additive one. In other words, if the beer is already partially carbonated, it would just mean that it will take less of the bottled gas to reach the target as long as the target is higher than the post fermentation level in the beer. Also, is it possible for the carbonation to get above 1 volume when it’s fermented with a blowoff vent, or am I conflating the concept of atmospheric pressure and volume?

 

[day_trippr]

If you search the string "residual carbonation from open fermentation of beer" you'll find a range of responses that center roughly around 1.0 to 1.2 volumes of CO2 - which actually surprises me because I had read decades ago it was 0.8 to 1.0 volumes - but either way you can see there's a pretty good start when you want just 1.2 volumes

Cheers!

 

[mac_1103]

the one thing neither our favorite carbonation table or this calculator consider is how much CO2 was already in the beer before the exogenous gas is added

Well it seems to be considering something. If you set it to 70F and 0.72 volumes of CO2 it will tell you to set your gauge pressure to 0.1; drop the desired volume of CO2 to 0.71 and you'd need negative gauge pressure.

The main thing that puzzles me is that the understanding that I have of gases, (poor at best), tells me that the forced carbonation is an equilibrium process

I'm pretty sure you're thinking about it correctly. The equilibrium CO2 concentration in the beer depends on the CO2 partial pressure in the headspace. At the end of an unspunded fermentation the partial pressure of CO2 in the headspace is 14.7 PSI. If you apply 7.9 PSI of CO2 gauge pressure the the partial pressure is 22.6 PSI.

 

[Closet Fermenter]

It's hard to know why, but while you pour, look closely at the tubing between the keg and shank. Is it solid beer or is there obvious foaming in the line itself? If there are bubbles in the line, beer gas is injecting into the beer path in the keg somewhere.

I just tried to pour a small cup. I watched the line, (purchased from you!) while I had the tap open and the beer appeared to be clear. I had almost convinced myself that it was the dip tube o-ring; this is an ancient 10 gallon corny keg. I thought that I replaced all the o-rings, but maybe I missed one or damaged it in the process.

Going to try a few more experiments, but I really appreciate this advice as I am sure that I will eventually run into this issue and hopefully I will have not destroyed the brain cells where this information is stored when that time comes!

 

[Bobby_M]

I have found splits and pin holes in the welds of the diptubes as well. One way to test against this and any diptube oring issue is to tilt the keg on its side enough for the beer to completely cover the diptube and liquid out post. If the foaming goes away, you know that was the issue. The other possibility that the gauge on your CO2 regulator is reading a few PSI lower than actual pressure. To test for that, lower the pressure to zero/turn off the tank and vent the system. Then pop the clear cover off your low pressure gauge. Carefully lift the pointer needle tip away from the gauge to get it to jump over the 0psi stop pin. Does it rest against the pin or is it showing lower than 0 now?