Fermenting under Pressure: Spunding Valve on a Sankey Keg?

As a huge german lager fan, and someone uninterested in the lengthy lagering wait, it’s inevitable that White Lab’s High Pressure Lager yeast would have come to infect my very subconscious. If this product is news to you, let me fill you in: the lagering game is more or less all about minimizing ester presence in the finished product - that is, make as little as possible during primary, and clean up most of what remains during lagering. While the normal approach is to pick a clean lager yeast, and ferment cold, where metabolism is slower (probably due simply to chemical processes running more slowly at lower temps - the yeast are in a liquid medium, and as such, heavily dependent upon the gods of chance to bring them food through collision and convection - but parts of that may be incomplete, I’m running sourceless here).

But some enterprising brewers, probably around the time that fermentation chambers became capable of higher pressures, CO2 began coming in tanks instead of through fermentation, and once fermentation volumes ballooned into the ~1000 barrel range, discovered that pressure could suppress ester production (I’m so unsure as to why that I’d be hard pressed to venture a guess). So, the trick becomes finding a yeast capable of holding up to the 15 psi common for the trick (fun fact - that’s the pressure about 30 feet down). Well, that’s where HP Lager commons in.

As to the practicality of such a maneuver, we live in the age of kegs, so it’s quite simple. One can either assemble a spunding valve with simple enough parts from McMaster Carr, or buy one for about $35 from a homebrewing store, and toss it onto the ball lock gas in (head space! Leave head space for the kräusen). Then, I suspect you can either set the psi right off the bat to 15 via the gas in (prior to adding the valve), or let the yeast give you the CO2 (No idea how this affects the ester production - definitely worth looking into or trying). And that’s it! The darned thing ferments at 68˚ for all of a week, ramps down to 32˚, sits there for maybe another week, and you’ve got pseudo-lager.

Now, how about doing this with a sankey keg, when you’re in a standard chest freezer that lacks the space for an elaborate tower of piping above the keg? Using a pressure grant *patent pending. The idea here is akin to a blowoff tube - you lock the beer out on the sankey, hook the gas in to some vinyl, and then attach the other side to the beer in line on a small, second keg - say a 4L or 1.5 gal mini keg, such as I use for my 1 gal system. To connect the beer thread on one side to the ball lock on the other, $5 will get you either a male beer thread-to-male ball lock connector, or a ball lock flare-to-male beer thread connector. Problem solved. Finally, toss the spunding valve onto the gas in on the pressure grant keg, and you’re good to go. Sanitize everything, and maybe pressurize slightly. I suspect that when I use this, I’ll go straight to 5 psi, and then let the yeast provide the rest - which may burn me! But then we’ll all be better brewers for it, which is worth the price of entry. Also, I may just start with the Rauchbier, and save the Helles for a safer, later trial