Saving head retention

Question

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?

Answer 1

Couple possible causes.

Keg line could be losing much of the carbonation. To calculate we need other info like, line diameter, tap style etc. Use a "keg line balancing" calculator like the Keg Line Balancing Calculator.

Low head forming proteins From extract the proteins for body are preset, usually around what a mash of 154° would give. It should still give a decent head, but steeping carapils or carafoam grains can help increase body and head retention in future extract batches.

beer clean glass you covered it pretty well, but the most important aspect is a "wet" glass.

excessive hot break if the boil was too vigorous the boil could have broke up all the head forming proteins. You want just a low rolling boil. Also the practice of removing hot break foam can reduce some head retention. I use fry scoop to push hot break back in rather than scoop it out. Foamcontrol drops in the boil help keep the proteins in the wort and prevent boil overs.

krausen loss If your fermentor didn't have enough head space and you lost a lot of foam out the airlock or blow off tube, this will also reduce head forming materials in the final beer.

high ABV beers will reduce head retention significantly.

Answer 2

Given that it won't hold carbonation the problem is not lack of foam positive agents nor the presence of foam negative agents. At least that is not the only problem. Neither is it a line balancing problem. I serve via 1 metre of 1/4 inch hose. It's not ideal, but I’ve pushed a Belgian Blonde through it at 20 psi. It arrives at the glass foamy but with lots of carbonation. There are few reasons why a beer will not hold carbonation. The most likely of which is that there is something in it which acts as a very effective nucleating surface. I've had this happen when I've frozen and defrosted a keg. That can sometimes cause limit dextrins and/or oxalates to precipitate out. These sharp crystals act as ideal nucleating points for co2 bubbles to form. The other thing that can form a nucleating surface is if your keg is at a few degrees below freezing. The pressure drop along the serving line allows small crystals of ice to form which is a very effective focus for nucleation.