I am interested in learning some of the intricacies associated with 'real ale'. I realize that out in industry, this is done in large stainless steel (or aluminum?) barrels with special corks etc etc in order to achieve the desired level of carbonation and aging. My question is, has it been attempted to replicate this keg conditioning using a corny keg, aside from simply adding priming sugar and letting it carb? Would a first attempt at this be as simple as hooking up a pressure relief of some sort to the CO2-in port, and letting it sit at 58F (ish) for awhile, or is the cask conditioning process much more involved than this?
Real Ale, that's
"beer brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide". (CAMRA)
As homebrewers, we can emulate this by:
Not pasturizing our beer...(ok that was easy!)
preparing the corny for use as secondary/fining/dispensing vessel by shortening the liquid out tube so not to pick up sediment, and adding a pressure relief on the CO2 in port.
racking from primary directly to the keg.
Using finings to clear the beer rather than a filter.
Optionally using pure nitrogen rather than CO2 to dispense, so avoiding the "extraneous CO2" part. (Personally, I'm not a purist, so I'd probably just use CO2, set to keep the volumes of CO2 in the 1.2-1.4 range.)
A lot of what we do as homebrewers is similar to traditional methods since we're not trying to or have the means to exploit economy of scale or produce sterile, filtered beer. For the most part, producing real ale can be a lot like normal homebrewing in kegs, apart from not using forced carbonation.
Depending upon how you naturally carbonate the beer, the pressure relief is optional. If you rack when the gravity is 4 points above final, then you don't need a pressure relief valve - the residual fermentables is the right amount to provide the appropriate level of carbonation at fermentation temperature (see link).
In the case where we don't know the exact FG or we hit final gravity before racking, then the pressure relief valve is the way to go. Set it from usual keg pressure charts according to the cellar temperature (typical 55-60F) and aim for 1.2-1.4 vols of CO2. If final gravity was reached, then add priming sugar. You can also add priming sugar even if FG wasn't reached - any excess CO2 will be bled off.
One problem with natural carbonation in a keg is that sometimes the corny lid doesn't seal - it takes a blast of CO2 or N2 to get a complete seal so the CO2 produced from fermentation is kept in the keg. Again, if you use CO2, that's more "extraneous CO2", but it's a personal choice if you think this will affect the beer.
It is really as simple as putting in some priming sugar and letting it go to "keg condition" for carbonation. In a true real ale situation you might rack from primary to keg when there is still <10% of the sugar remaining. In this case you are not adding any priming sugar.
But there's nothing more to it than sealing the keg and getting the beer to carbonate on the trapped pressure. Just like bottling. A measured amount of sugar will produce a measured about of CO2 and carbonation. No need to hook up a "pressure relief of some sort".