A photo of a pretty pour, hand-pumped from a cask of Peg Leg Stout —brewed by Heavy Seas Brewing (of Baltimore, Maryland)— is this week's Pic(k) of the Week.
- The cask was stored in an under-bar-counter refrigerator, kept at 50 °F.
- It was vented, tapped, and served, standing upright, using a cask widge.
- To forestall spoilage, a cask breather provided blanket carbon dioxide (CO2) coverage, but at zero pressure. *
Arlington (Clarendon), Virginia.
22 October 2014.
- * To clarify about the zero pressure thing...
- The atmosphere exerts pressure on us, which, at sea level, is 14.7 pounds-per-square-inch (PSI), depending upon weather conditions. A standard CO2 gauge measures only any additional pressure greater than atmospheric. Thus a gauge showing 1 pound-per-square-inch-gauge (PSIG) is actually releasing CO2 at one pound PLUS atmospheric pressure.
- A cask breather does not really pressurise a cask. It's an aspirator valve that responds to the slight vacuum created when beer is pulled from a cask, by releasing CO2 at atmospheric pressure (or maybe a wee, wee, wee bit more) —thus, effectively, zero PSIG— completely filling the space vacated by the beer pulled out with CO2. This CO2 rests atop the beer like a blanket, accomplishing two things. It prevents ingress of air —and the oxygen in it— into the cask, which would oxidize, that is, stale, the beer. And, it slows the flow of CO2 —dissolved in the beer— into the headspace, that is, it slows the beer from going flat.
- With a standard CO2 regulator, a setting of '1' would permit enough CO2 to flow into a cask to actually carbonate it, thus making it kegged beer rather than cask-conditioned beer, albeit at lower pressure additional beer carbonation. And a setting of zero would prevent any CO2 at all from flowing into the cask, and thus prevent little beer, if any, from being pulled out.
- By the way, using nitrogen instead of CO2, or even mixed gas —so called Guinness gas (a blend of nitrogen and carbon dioxide)— would also protect the beer from oxidation, but it would NOT protect the beer from going flat, that is, losing CO2 into the headspace.
- A final observation. If the cask has not been properly vented before service, the excessive CO2 in solution and the headspace will prevent the cask breather from operating correctly. And, defeats a purpose of cask-conditioning in the first place.