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CO2 foam

Posted: Sun Apr 07, 2019 4:58 pm
by Peterpasha
Backstory: I have been fermenting lagers in a ball-lock keg in my small old keezer. It's just big enough for one keg and a growler for the blowoff tube. I'm using a blowoff tube connected a disconnect on the gas-in post in which I have removed the poppet cause I didn't want any kreusen gunking up the post. I've done a couple of lagers like this with a little sucess, it hasn't been brilliant, but it hasn't been a disaster until now. I haven't had the best success with transferring under pressure, so I've been using an auto-siphon to transfer from the fermenting keg to a secondary keg for the longer lagering. The previous brew before this one, I had a brain-fart senior's moment, and pulled the disconnect without venting the fermentation co2 from the keg. Needless to say, there was a magnificent geyser of beer!

Current situation: About 2 weeks ago, I decided to transfer the beer from the primary keg to the secondary keg, it had been in the primary for over 2 weeks and I wanted to get set up for another lager brewday. I pulled the pressure relief pin and heard a lot of gas venting from the keg. After about 45 seconds of this, I started to get foam through the pressure relief and I stopped venting. I figured that venting had caused the gas to come out of suspension in the beer and had produced a large head in the keg. So I figured no harm, no foul, I'll put it back in the keezer for another week until the head can reduce, figuring the cold lagering temperature would help. The keezer is set to 40F for lagering. But after a week, I still had an incredible amount of foam coming through the vent.
I gave it another week at 40F and tried again, same result. Now I figured that I had no way to relieve the still-considerable pressure inside the keg, so I might as well try to transfer it under pressure to a secondary keg using the naturally occurring co2 as a propellant.
But all I got was foam. I could see nothing but foam in the transfer tubing, so after about 5 minutes I stopped that and put a picnic tap on a beer line and pulled a glass. Foam.
I don't know what else to do other than transfer this to an open bucket and wait for the foam to dissipate before transferring it to a secondary keg for longer lager, but by then the exposure to oxygen will be fatal.


Title: American Pils
Author: Wharf Works

Brew Method: All Grain
Style Name: Classic American Pilsner
Boil Time: 60 min
Batch Size: 5 gallons (fermentor volume)
Boil Size: 6 gallons
Boil Gravity: 1.045
Efficiency: 50% (brew house)

Original Gravity: 1.054
Final Gravity: 1.009
ABV (standard): 5.93%
IBU (tinseth): 35.08
SRM (morey): 10.43
Mash pH: 5.53

10 lb - Pilsner (66.7%)
2 lb - Pale 2-Row (13.3%)
2 lb - Carapils (Dextrine Malt) (13.3%)
1 lb - Munich - 60L (6.7%)

0.5 oz - Magnum, Type: Pellet, AA: 15, Use: Boil for 60 min, IBU: 29.75
0.5 oz - Saaz, Type: Pellet, AA: 3.5, Use: Boil for 30 min, IBU: 5.33

1) Temperature, Temp: 152 F, Time: 60 min, Amount: 18.75 qt
2) Temperature, Temp: 170 F, Time: 20 min, lauter
3) Sparge, Temp: 170 F, Time: 20 min, Amount: 12 qt
Starting Mash Thickness: 1.25 qt/lb

Fermentis / Safale - Saflager - German Lager Yeast S-23

Anyone experienced anything like this?

Re: CO2 foam

Posted: Mon Apr 08, 2019 8:25 am
by McGruff
I may be wrong, but you fermented this lager and didn't vent the c02? If this is the case, you carbed up your lager from the yeast spewing out c02 during fermentation? I have read about fermenting beer under pressure, but don't really understand it. Hopefully someone will clear this up.

Re: CO2 foam

Posted: Mon Apr 08, 2019 9:13 am
by Peterpasha
No, I had a blowoff tube attached to a disconnect on the gas-in post. I had removed the poppet from the post so it was clear sailing and I looked in on it from time to time in the early stages and there was plenty of bubbling going on from the tube, so I know it was clear, at least in the beginning.

Re: CO2 foam

Posted: Mon Apr 08, 2019 11:51 am
by Beert
Seems like a venting problem. Did you remove the stem and spring from the disconnect? Without the poppet the disconnect would have remained closed, but this doesn’t explain why you were seeing bubbles coming from the blow off tube.
Although...I have had the experience of the blow off tube getting clogged early during fermentation and subsequently the stopper blew off the carboy. In your case, using a keg, the fermention co2 would have been forced into the beer.

Re: CO2 foam

Posted: Tue Apr 09, 2019 9:30 am
by Peterpasha
I hadn't removed the poppet and spring from the disconnect, hadn't even thought about that. I guess the fermentation was so active in the initial stage, that the pressure forced the poppet open on the disconnect but not so active to open the relief valve. I guess I can be thankful for that.

Re: CO2 foam

Posted: Tue Jul 23, 2019 11:28 pm
by Willym
This is a very interesting (and unfortunate) problem. You have a lot of CO2 in that keg!

I've fermented a cider in a closed keg and it got up to 60psi. I relieved the pressure over many short pulls of the pressure relief valve, over multiple days.

Below is good explanation of gas in liquid solutions. ... s_in_Water

It's the sudden pressure drop that reduces the gas solubility in the beer and causes the foaming.

My suggestion is to keep trying to bleed it off using the pressure relief valve over many short bursts. As soon as foam starts to exit the PRV, wait a few minutes and repeat. Lower the temperature of your fridge to 0 C so that the pressure in the keg drops a bit and the pressure difference between the keg and the open atmosphere is lessened.

Trivial solution:
Transfer to another (less)pressurized keg (counter-pressure). You'll need to figure out the pressure in the lager keg using a gauge attached to one of the posts. Use your CO2 to pressurize the destination keg to something like 10 PSI less. If the flow stops, dial down the CO2 on the destination keg and bleed some pressure off to maintain the 10ish PSI pressure drop.
Now you have a slightly-less over-pressured keg! ;) You could keep going back and forth?