I have head retention problems in an extract bock, and I've been working my way through the potential issues. It's in a keezer.
- Line is 3/16, length is 8ft
- Pressure is 14psi (I live at 5,000ft)
- Pour time is 8-9 seconds
- Fan circulates air
- Keezer is 38F
- Lines are coiled on top of keg, no CO2 breakout in the lines
- I'm confident in the carbonation levels, it has been slow-carbing for months
Once the beer hits the glass, the CO2 rapidly breaks out, forming glassy bubbles instead of white foam, and it sounds like a soda. A strong head of these glassy bubbles appears, but quickly dissipates leaving the beer completely flat.
I've experimented with chilling the glasses, which helps but does not solve the problem.
I've worked on "beer clean glassware", scrubbing with a brush & baking soda/salt. They might not be "beer clean", but commercial beer has good head & lacing in the same glasses vs my bock.
At this point I'm thinking I must have some detergent traces in the beer- I used to clean my kettle and a few other elements for the boil with soap. I stopped a while ago, but there could still be residue.
Any ideas of other possible causes?
If it is detergent in the beer, is there anything I can do to save it?
P.S. I think I can rule out a CO2 leak in the gas side of the system, because my 5lb CO2 tank has been holding pressure for 3 months, and because the freezer is not full of CO2
Minor update: I got to thinking. I have a one-way check valve on the gas line. I began to wonder if it had a forward pressure (like a diode's forward voltage), i.e. the valve closes when the pressure across the valve is too low, resulting in a lower pressure on the other side of the valve. I swapped to an ordinary quick disconnect with no check valve, and some gas began flowing into the keg! So while the regulator was at 14psi, the keg was at something lower. Likely not much lower, but it was an interesting discovery. Does anyone know if there is a "standard forward pressure" for check valves?