Anyhoo, onto the Cask v. Real Ale argument (It's quite clear-cut, surely, Real Ale is "matured by secondary fermentation in the container from which it is dispensed". And normally sucked rather than blown out like "keg" would be)
But, in an effort to clarify the situation, we asked our expert Professor Branestawm to explain the concept of "vols" of CO2 for us.
"Consider if you will Stringers", He began, "A pint of liquid which contains 1 vol of a gas dissolved in it. If we magically removed the liquid, we'd be left with the pint full of the gas."
OK, Professor, we've got that, but how does this help us understand the carbonation and maturation "histories" of the typical Cask v. the lovely Real Ale.
"It's simple", he exclaimed, and continued "Please note - what I say here is illustrative and assumes a few things (open fermenters for one), i.e. I've made these numbers up, so you'll have to take my word for it that they are about right!"
We'll take your word Professor, please, continue.
The professor pulled a scrap of paper from his pocket and flourished a curious and elaborate fountain pen. "My own design." he said, before rapidly drawing up the following table:
Vols CO2 in: Cask Real Ale Start Fermentation 0 0 End of Fermentation ~0.8 ~0.8 Post Chill ~0.5 ~0.5 Post tank conditioning 1.4 - Into Cask 1.4 ~0.5 Out the door 1.4 1.4 On stillage (in pub) 1.5 1.5 On service (post venting) 1.1 1.1
"Which is to say", he went on, "Real develops at least two thirds of its condition (spending at least a week) in the container from which it's dispensed. i.e. it's predominantly Cask Conditioned, whereas Cask might pick up ten times less in cask. i.e. it's predominantly Tank Conditioned. i.e. Pretty much all of the secondary fermentation occurs in tank - not in the cask!"
Before we could say anything, he added, "Of course there's room for brewers to work in-between these extremes, tank conditioning up to, perhaps, 1 vol and finishing conditioning in cask."
But Professor, what's the problem with good beer being conditioned in tank, provided it's getting an appropriate period of maturation on its own yeast? Surely this is the key thing? And if tank conditioning makes this easier, why not?
"Well you see" said the Prof, leaning in conspiratorially, "this illuminates an issue with CAMRA's definition of Real Ale: Much of what is held to be the kind of beer that CAMRA is in favour of can only be called cask conditioned in a very narrow sense - some small amount of conditioning (secondary fermentation) in the cask is unavoidable when we're dealing with live yeast, but it's not a significant part of the production process."
We see Professor, but surely, brewers wouldn't call their beer Real Ale if it wasn't?
"Precisely!", cried the professor, "Only CAMRA ever called these things Real, the producers always called them Cask Ales, which they indisputably are, being ale and in cask!"
He smiled and shook his head. "They're not bloody stupid you know, these brewers!"
Many apologies to (the estate of the late) Norman Hunter.