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-   -   Foam but no carbonation (http://www.homebrewtalk.com/f35/foam-but-no-carbonation-189353/)

stoutaholic 08-03-2010 11:07 PM

Foam but no carbonation
I know this question has been asked before, but none of the threads I have found have actually explained the phenomenon that is occurring. Essentially, when I dispense the beer from my keg, it pours complete foam, but when the foam settles out, the beer in the glass is completely flat. Anyone know what is going on here?

This doesn't seem to be a simple issue of balancing the system. I could reduce the pressure in the keg, increase the line length, etc. in order to pour a slower or less foamy glass. What I don't understand is how the pour can be complete foam without being noticeably carbonated at all. It is as if, once the beer reaches the glass, all the CO2 instantly bursts out of solution as foam, thus leaving the beer devoid of CO2. But I don't understand why this would happen, if this is what is actually happening.

PintOfBitter 08-03-2010 11:27 PM


Originally Posted by stoutaholic (Post 2197269)
... It is as if, once the beer reaches the glass, all the CO2 instantly bursts out of solution as foam, thus leaving the beer devoid of CO2. But I don't understand why this would happen, if this is what is actually happening.

You're right about this. beer is going from keg pressure to ambient too quickly, which is causing virtually all the CO2 to come out in foam. You know the beer is getting carbonated, or the foam wouldn't happen at all.

How long are your lines and what is your serving pressure?

wildwest450 08-03-2010 11:28 PM

Did you do an extended high psi force carb. Give it a little shake maybe?

sniemeyer 08-04-2010 01:21 AM

I have a 12 foot 3/16" line. I can see the beer in the line, without any foam, but as soon as it leaves the cobra head dispenser, it turns into foam. I also tried it with a chilled glass, with the same result. I am actually not adding any additional serving pressure, just relying on the pressure existing in the keg (my intention was just to bottle a six pack with my counter-pressure bottle filler and then adjust the pressure in the keg to serving pressure later. I wanted to ensure that, after losing carbonation in the bottling process, the beer in the bottle would still be sufficiently carbonated).

The beer may very well be overcarbonated, as I used a 0.5 micron stone, set the pressure at about 20 PSI with the beer at 32 F, and let it sit for two days. This is a Belgian Dubbel, so I want the carbonation level to be about 3.0 to 3.5 volumes. It may not even be possible to use a counter-pressure bottle filler at that level of carbonation, but I am still confused about why all the CO2 suddenly bursts out of solution, even when dispensing to a glass with a cobra head. If the beer was SIMPLY overcarbonated, I would expect the beer to foam, pour too quickly, etc. but I would not expect the beer remaining in the glass, after the foam has dissipated, to be completely flat. This is what seems odd to me. It is as though somehow the CO2 needs to be "bound" more completely to the beer itself.

sniemeyer 08-04-2010 02:42 AM

I've read some more posts on this topic and it sounds like the basic principle is that the more foam you have, the less carbonation there will be in the beer. So if some problem with the system (overcarbonation, lines that are too short) is causing the beer to foam, then this will result in an undercarbed beer in your glass/bottle. Therefore, even though the beer is HIGHLY carbonated in the keg, this can actually led to very LOW carbonation in the beer, if the high carbonation in the keg results in an extremely foamy pour. All the foam in the pour that later condenses into beer has apparently lost all of its carbonation in the process of being foam. So I will reduce the level of carbonation in the keg and see what happens.

malkore 08-04-2010 10:35 PM

Clean your cobra tap 'guts'. If you've got crud in there forcing the beer out through a restricted opening, it pushes the CO2 out.

How long does it take to pour a pint at 20psi? If its fast, your system isn't balanced.

I HIGHLY recommend getting those mcmaster epoxy nozzles and jamming 2-3 down your dip tube to slow the beer flow.

Those things solved my kegging woes 100%

Pimp Juice 08-04-2010 11:34 PM

Simply sounds over-carbonated.

rocketman768 08-05-2010 12:19 AM

Are you serving your beer at 20 psi? Usually, I can barely get away with serving at 10 psi. You probably should crank the psi down (maybe even down to 5 psi) when you serve so that beer isn't coming out so fast and knocking CO2 out of suspension.

sniemeyer 08-05-2010 08:56 PM

So, working on the assumption that my beer was overcarbonated, and that the foaming was CAUSING the lack of carbonation in the glass, I used the CO2 purge valve on the keg to let off CO2 until there was no longer any audible gas leaving the keg (maybe 20 to 30 seconds worth of purging). I then poured myself a glass using the residual pressure in the keg -- poured fine, no foam, but also very little carbonation in the glass. So obviously the situation was that there was a high level of CO2 pressure in the keg, but the beer had absorbed very little of the CO2. So this leads me to a new question, which I will start as a new thread -- how do you get the force carbonation procedure to work successfully? Apparently I am doing something wrong ...

Rhoobarb 08-05-2010 09:12 PM

Also - and this may not be the problem - check for any leaks in the 3/16" tubing. I had a tiny leak develop last weekend where the tubing met the barb on the faucet. The tubing had been on there for four years, had gotten worn and was leaking just enough to not be noticeable except at 20-30 psi. I cut off the 3/4" of worn material, reconnected everything and it was good as new.

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