Could incomplete initial fermentation cause foaming between keg and faucet?

Hey there,

So a friend of mine brewed a golden ale with oats recently. He put it in the keg without taking any gravity readings, and I personally think he kegged it too early (this may or may not matter, I'll get to that in a second...) as it had a pretty heavy mouthfeel initially. After kegging and force carbonating, it seemed like it had a ton of foam from the kegerator that it was in (his then roommates). We took it to his newly purchased home for moving day to keep the troops hydrated. Still lots of foam there, in a trash can with ice, different QD and lines and faucet.

There was about 2 gallons or so left over after moving day so we brought it to my garage and put it in my kegerator. I have 10' 3/8" thick wall beer lines with Perlick faucets. I was still seeing lots and lots of foam, so I cracked the fridge door and sure enough, it was foaming IN THE LINE as it left the QD, all the way up to the faucet. I was getting about 1/4 glass of beer and 3/4 glass of foam. After checking all the connections and talking to my LHBS, the suggested I check/replace the o-rings on the beer out post and diptube, which I did. Still seemed to have a lot of foam. I let it set for 2 weeks or so, not knowing what to make of it. I checked it again today as I was going to tear into his keg and see if I could fix it, but I got a perfect pour, the first half glass with lots of yeast. Dumped that out after sampling and poured another pint and it came out clear and without any real foam. I checked carbonation and it was spot on, and it foamed if I let the beer fall 12" or so into the glass. Head retention was good. It also tasted a fair bit dryer than I remember it tasting before, without the thick mouthfeel.

Is it possible that since he kegged it before fermentation was complete, this was causing the foaming in the line before it even reached the faucet? And after 2 weeks at 40* (very slow fermentation, I realize, if any at all) it finished out and there is no longer much yeast in suspension? I'm just trying to wrap my head around why this awful foaming problem would just stop on its own in the kegerator without external influence...

Thanks and cheers!

It seems like there's a lot going on here, I don't know if I would blame possible incomplete fermentation. You really wouldn't be getting any fermentation at 40 degrees with an ale yeast, and carbonation can definitely affect the mouthfeel.

Things that stand out to me:
1) It sounds like he did a high-pressure force carbing. How'd he carb it? How long did he let it settle afterwards?
2) You moved it and were getting foam. How long did you let it settle after moving it?
3) After a few weeks chilling in your kegerator it finally pours perfectly.

My guess: it was overcarbed initially. You drank most of it, it foamed like crazy for 3 reasons: you just moved it, it was overcarbed, and probably you were using a picnic tap with a short hose. It foamed so it lost all carbonation in the glass, hence the thick mouthfeel. Since you drained off a lot of the keg, you created lots of headspace so the excess CO2 could come out of the beer and re-equilibrate. At that point, you moved it to a normal system and let it chill/carb back up for 2 weeks, after which it poured perfectly.

Sounds like a classic case of overcarbed beer. This is why so many people here preach the "set and forget" method of force carbing.

I agree...probably just overcarbed beer.

ale yeast is inactive at 40 degrees. no fermentation would have taken place.

So, thanks for the replies. I guess I assumed that if it was overcarb'd it would be foaming as it came out of the faucet, not as it left the keg. Seeing foam in the beer line is a little weird to me.

CO2 will come out of solution if the pressure on the keg isn't equal to the equilibrated CO2 pressure inside the beer. It does this to try and balance things out, and you often see it in the line. For example if you left the beer at 15 psi for 3 weeks then purged and set the regulator at 12 psi, you'd see the same thing. That's basically what happened here.