Post
by Kev888 » Sun Jan 14, 2018 12:49 am
If the intention is to replicate truly traditional cask-conditioned beer at home, possibly the only way one can fully do that is to use small enough vessels that they won't oxidise and go too flat before you finish them. For many of us that isn't practical, so some kind of compromise is needed. In particular, filling the increasing head-space with CO2, rather than air, stops the beer becoming badly oxidised in relatively short order. That is often achieved with ultra-low pressure cask breathers (or reversed propane regulators) - probably in part because these are in a grey, least objectionable area wrt CAMRA.
But in practical terms, most cask beers have a little condition/carbonation and if they have been broached for long enough to go very flat then this too has a detrimental affect IMO - even if served via beer engines. To prevent this where beer is drunk more slowly, enough pressure is needed in the head-space to maintain equilibrium. For cask-like levels I would not directly follow the equilibrium charts frequently used to gauge force-carbonating pressure, but something around the upper end of their 'under-carbonated' range works for me, to keep the condition as it should be, indefinitely. A normal primary+secondary regulator combo can go low enough at normal ale temperatures (say ~13c), even a decent primary regulator alone can manage if necessary.
There isn't really a need to reduce pressure between storing and dispensing sessions. Such things can cause variation, depending on how long the dispensing session is (or if forgotten afterwards), and in some cases dropping the pressure below equilibrium to dispense can cause foaming. Beer engines can be run via a demand valve, to prevent beer pushing through them if there is sight pressure in the cask/barrel/keg etc. Though not all types of keg are well suited to sealing at low pressure, so it may be necessary to juggle pressures there. If one were setting out with cask-like beer particularly in mind I'd suggest that a type of cask, keg or barrel purpose-designed to seal at any low (or no) pressure would be the way to go.
Kev