This month’s Session takes a lovely turn back to its roots for it’s 3rd birthday, and we’re back to a “beer definition” type of topic. This month, the topic is cask-conditioned beer and it is being hosted by Tom Cizauskas at Yours for Good Fermentables. You can read the the announcement to get the full gist of the topic, and make sure you head back over to YFGF to read the post round-up later.

Cask-conditioned beer is actually a tough topic for me. While I love it, I don’t have any sort of style specific knowledge about it. In addition, barring the occasional cask beer festival, there just aren’t that many casks available around me on a regular basis. I hear rumors, however, that Alivia’s Durham Bistro will soon have the first operating Beer Engine in my local area which got me thinking:

How exactly does a beer engine work? You see the hand pumps at bars all the time, and you see bartenders muscling a pint of cask ale up for you, but I’m not sure I’ve ever understood exactly what goes on in there. So I did a little bit of research.

The point of a beer engine in the first place was that the cask that you were serving out of was not at the bar. In a classic pub setting (and I’m using classic to mean “prior to refrigeration”) it was likely in the cellar, where it had been conditioning and where it was generally going to last the longest. You used the beer engine to move the beer up from the cellar and into the customer. Today, this isn’t always true. Many of the beer engines that I’ve seen are set up merely feet from the cask the serving out of the hand pump is considered to be part of the cask ale experience, rather than a necessity of moving the product.

As it happens what’s going on inside of a beer engine is simple – like frighteningly simple. With the giant swan neck and big ceramic handle, I assumed that something complicated and Victorian was happening below decks, but here’s the truth of the matter:

It’s just a fancy-looking piston hand pump, and that’s it. There’s a one-way valve inside the pump just below a piston chamber. When you draw on the lever, it pulls the piston up, dispensing the beer above the piston – forcing it up into the swan’s neck – and drawing more beer into the chamber. Pushing the handle back to its original position merely pushes the piston back into place, closing the one-way valve and returning it to a position at which point it can draw more beer from the keg.

A meager diagram of a hand pump.

The poorly-dawn diagram that you see to your left is essentially the same thing that you can see going on in the upper-right corner of the 1808 diagram above. Beer comes in from the cask below the pump, through the one-wave valve. The piston draws it up and then pushes it out the swan’s neck above. The cask has to be open and breathing or you’ll create a vacuum in the line (and cask) and won’t be able to draw beer which is, of course, why casks have such a small shelf-life. Not only are you drawing oxygen into the cask with each pull, but you also have a container which isn’t under pressure. The ale will de-gas on its own over time.

If you’re drawing beer up from a cellar, I would imagine that the weight of the liquid could be quite an issue and that you’d need quite an arm to pull it over a particularly long line – it is a great argument for keeping the keg close at hand.

The last optional piece on the beer engine is the sparkler on the serving end of the swan’s neck. It is totally an optional piece of equipment and I expect there will be at least one post around today’s Session that will talk about serving with a sparkler vs. without. The sparkler is just a little nozzle with holes in it, it means that the beer is broken into multiple airy streams as it’s poured into your glass instead of one large stream. It greatly increases the head on your pour and releases a lot of carbonation in the process. Many people argue that it also scrubs hop aroma because of this large release of CO2. Again, I suspect others will discuss this. Knowing how that beer got into my pint is good enough for me today.

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Categories: Sessions
Posted By: erik
Last Edit: 05 Feb 2010 @ 12 26 PM

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