Getting Too Much Foam From My Keg

Question

I’m getting way too much foam from my keg when I’m pouring. I started out with pressure at 12. After 4 days my beer was awesome at about 35 degrees. After about 4 more days I started getting much more foam. So I then cut the pressure to about 6 but still way too much foam.  Any advice on how to fix this?

Answer

Carbonation is a mechanical process. The CO2 has to turn into carbonic acid to become stable (the technical term is “laminate”) and this takes 3 to 4 days, but can get more refined with time. The basic math is a time/temperature and headspace equalibrium equation to achieve balance. To carbonate, you are typically 30% to 50% higher than you intend to serve. Serving pressure is a factor of line resistance and rise to the tap.

If you’re pushing it with much lower pressure than the level of carbonation in the beer you’ll get a lot of foam because the CO2 is coming out of suspension very rapidly. The flip side, if you push it with too much it’ll foam because you’re slamming it into the glass.

Generally, if you pour it with about 5psi above the carb level, you’re good to go. You can’t leave it at that pressure because then it’ll carb the beer more! Also, don’t forget to open the valve all the way when you’re pouring. If you only release it part way it’ll just shoot foam.