Gravity v.s Beer Engine

Written By: Mike Warner

One of the defining elements of cask beer is that it is served without any added gas or carbonation. This differs from draught beer, where carbon dioxide and nitrogen are added for carbonation and to push the beer out from the keg, through the tap and into your glass. As cask beer is naturally carbonated and conditioned within the keg, a different method of dispensing the beer must be employed. This can either be done through a beer engine or by gravity.

Gravity dispensing predates the beer engine. In this case, a tap is placed in the front of the cask and the beer comes out by the simple force of gravity when the tap is opened. This allows for cask beer to be appreciated in a pure form, as there is no agitation of the beer from the cask to glass. The gravity dispense method also makes it harder to mask flaws such as an under carbonated beer.

Gravity dispensing is most often used at beer festivals, special events or at bars without beer engines, which usually means they only serve cask beer one or two nights a week. The problem is that most often the cask is just sitting on the bar (or on a table in the case of beer events), making it hard to regulate the temperature of the cask. Cask blankets (basically flexible ice packs) can be used to help keep the cask cool, but casks served through gravity must still be consumed very quickly.

The alternative to gravity dispensing is the beer engine. Before modern refrigeration, the beer engine allowed a cask to placed in a cellar and have the beer drawn up to the bar by pumps. This extended the life of a cask by placing it in a consistently cooler area. Casks are now stored in fridges most of the time, but the beer engine remains largely the same. (There are electronic pumps, though you’re not likely to come across one. If your server isn’t pumping the beer, chances are you’re secretly getting draught beer from a tap made to look like a hand pump.)

Unfortunately, beer engines are not perfect. If the line from the cask to the spout is not properly insulated, the beer could be above ideal temperature in your glass. Hand pumps can also agitate the beer, taking away some of the subtleness of cask beer. Sparklers are another contentious issue surrounding beer engines. Essentially, sparklers are plastic caps attached to the spout of a beer engine. They are perforated with small holes that spray the beer into the glass when it comes out of the spout. This helps to create a nice head on a pint of cask beer, though some also argue that it takes away from the flavour and aroma of cask beer. It’s really a question of personal preference and source of nerdy pub arguments.

I would never say that one method of serving cask beer is better than another, though you’re welcome to come to your own conclusions. In my opinion, coming up with an answer is hard because of the very nature of cask beer. As a living and evolving beer, no two casks are ever the same. Plus there is the influence of the bar/restaurant and how they treat casks. There is more to the story than strictly how a cask is served, though it is an important part to creating an enjoyable pint. It never hurts to ask how a cask beer was served – the gravity or beer engine part is usually pretty easy to see, but see if they use a sparkler or ask where the casks are stored in relation to the hand pump. Over time you may find a preference to one method or take sides in the sparkler debate. Or you may just develop a stronger appreciation for cask beers, the breweries that make them and the people the serve them. There’s nothing wrong with that either.