When the beer arrives at the pub it needs to undergo its secondary fermentation before it can be served. The usual practice is for the casks to be placed in a cellar.
Some pubs keep their beer in a special cool room on the ground floor and a few keep their beer behind the bar – preferably with some modest external cooling system. Real ale is served at cellar temperature 11-13°C, which is somewhat cooler than room temperature. If real ale is too warm it is not appetizing, it loses its natural conditioning (the liveliness of the beer due to the dissolved carbon dioxide) but if is too cold it will kill off the subtle flavour. Some cask beers are meant to be served cooler than others and have been produced to provide a refreshing alternative to lager in the summer.
How long a beer needs to stand depends on the beer, particularly its alcoholic strength and how vigorously it ferments. Some modern beers have a weak fermentation and may clear within twenty four hours. That does not mean that these beers have conditioned sufficiently and to serve them as soon as they are clear is not necessarily to serve them at their best.
The cask is wedged on its side, to encourage the sediment to sink into the belly. Every cask has two plugs where instruments can be knocked into the cask by force. The cellar person knocks a small wooden peg into one. A hard wood peg seals the cask, a soft wood peg allows carbon dioxide to escape. By alternating hard and soft pegs as needed, the cellar person carefully controls the natural carbonation of the beer. Too high a carbonation and the beer will have a nasty bite, too little and the beer will be flat.
When the fermentation is about right, a tap is knocked into the cask at the other entry point. The cellar person will check that the beer is clear, has the right level of carbonation, and has lost the unpleasant flavours associated with beer that is too young. When the beer is ready to serve, the tap is connected to the dispense system. How long the beer lasts depends on its strength – stronger beers are more robust, and may last for weeks, weaker beers are normally drunk within a few days. This is why turnover is so important for quality – ideally the pub sells enough beer that you always drink it at its best.
Serving real ale
The most common means of dispensing real ale is the beer engine – a tall handpump on the bar, which operates a simple suction pump. When the handle is pulled a half pint is drawn into the glass.
Sometimes in the Midlands and North an electric pump is used. This simply uses a machine to do the same work as the handpump in drawing beer to the bar. In appearance electric pumps can be confused with the dispensers used for keg beer. Real ale can of course be poured straight out of a cask behind the bar, and this is known as gravity dispense. In Scotland a tall fount is often used. This drives beer to the bar with air pressure. There is one final point about the beer’s journey to the glass. Serving beer through any handpump agitates the beer to some extent and aerates it. Some dispense systems deliberately maximise this agitation. A sparkler is a tight nozzle, normally at the end of a long ‘swan-neck’ tube. Beer must be forced through the tight holes, often requiring several strokes of the handpump. This agitation produces a thick creamy head; it also removes much of the natural carbonation from the body of the beer, and drives much of the hop bitterness into the head of the pint. Such dispense is traditional in some parts of the North, and beers are brewed there with this in mind.
Glassware can affect the appearance, aroma and taste of cask beer and a dirty glass causes the beer to lose its head.