Cask ale or cask-conditioned beer is the term for unfiltered and unpasteurised beer which is conditioned (including secondary fermentation) and served from a cask, usually without additional nitrogen or carbon dioxide pressure. Cask ale may also be referred to as real ale, a term coined by the Campaign for Real Ale, often now extended to cover bottle-conditioned beer as well.
Bottled beers were commonplace by the 17th century for the well off who didn’t wish to drink in public inns, or who wanted to take a beer with them when fishing. Such as the famous story of Alexander Nowell, the Dean of St. Paul’s, who, in 1568, left his bottled beer by the river bank, and upon returning a few days later discovered the bottle opened with a bang and that the contents were very tasty. But while the middle and upper classes could indulge themselves with such expensive luxuries, the ordinary folk continued to drink their beer served direct from the cask. The famous ale that was shipped to India was delivered in casks, and only transferred to the bottle for the civilian middle classes; the troops drank their beer the same way they drank it back home, from flagons filled direct from the cask. But as beer developed and became paler and lower in alcohol, so it became more difficult to keep it fresh tasting in the cask, especially in countries with warmer climates. By the late 19th century commercial refrigeration and Louis Pasteur’s flash heating method of sterilisation prolonged the life of beer. In Britain’s cooler climate these methods did not catch on. At least, not immediately.
Of course not all beer in mainland Europe is pasteurised; there are plenty of examples of unfiltered, unpasteurised beers, but these will commonly be served from a chilled container under pressure: a keg.
Traditionally draught beer came from wooden barrels, also called casks. In the 1950's these began to be replaced by metal casks of stainless steel or aluminium, mainly for quality reasons as they could be sterilised and the beer was therefore less likely to spoil, but also for economic reasons. An additional benefit of the switch to metal casks was that staling from oxygen in the air could be reduced. Subsequently, in the early 1960's a form of metal cask, known as a keg was introduced which allowed for more efficient cleaning and filling in the brewery. The essential differences between a traditional cask and a keg are that the latter has a concentrically located downtube and a valve that allows beer in and gas out when filling and vice versa when beer is dispensed. Also kegs have a simple concave bottom whilst the barrel or cask design allowed sediment to be retained in the cask. This aspect of keg design meant that all the beer in the keg was dispensed which therefore required that the beer be processed by filtration, fining or centrifuging, or some combination of these, to prevent sediment formation. Lastly, kegs have straight sides unlike the traditional barrel or cask shape. In order to get the beer out of a keg and into a customer’s glass, it can be forced out with gas pressure, although if air or gas at low pressure is admitted to the top of the keg it can also be dispensed using a traditional hand pump at the bar. By the early 1970s most beer in Britain was keg beer, filtered, pasteurised and artificially carbonated. This change was largely driven by the customer's dislike of sediment in his beer. However, most British brewers used carbon dioxide for dispensing keg beers. This led to beers containing more dissolved gas in the glass than the traditional ale and to a consumer demand for a return to these ales. However, in Ireland where stout was dominant, the use of a mixture of carbon dioxide and nitrogen for dispensing prevented the beer from becoming over carbonated. Some of the last remaining natural beers in the world were about to disappear forever. Though rare examples of natural beers could still be found in the farmhouse beers of Northern Europe and the maize beers of South America for example, in essence the last great stronghold of natural beer was about to be wiped out. And that’s when the Campaign for Real Ale (CAMRA) stepped in in Britain to save what they came to term Real Ale.
Cask-conditioned beers and bottle conditioned beers are often referred to as real ales, though by the terms of CAMRA's definition not all cask or bottle conditioned ales are real ale; in particular, some American-style brewpubs may use collected carbon dioxide during the serving process which would disqualify them from claiming real ale status.
The use of cask breathers is considered “extraneous carbon dioxide”, so CAMRA does not endorse this method.
Cask ale brewing starts the same as that of keg beer. The same brew run could be used to make cask, keg, and bottled beer. The difference is what happens after the primary fermentation is finished and the beer has been left to condition. While pasteurised keg and bottled beers are then subjected to filtering and flash heating, the beer for the cask is simply placed in the cask in its natural state. Finings, such as isinglass or Irish moss, are placed in the cask to assist removing the yeast and clear the beer. Extra hops and sugar may also be added. The cask is sealed and sent off to the pub. In this state it is like a bottle-conditioned beer and, like bottle-conditioned beers, the beer will continue to develop for a certain period of time. Also like bottle-conditioned beers, the length of time the beer can last in the cask will depend on the nature of the beer itself: strong, dark beers can last for months; light, delicate beers need to be tapped and sold quickly. Stronger beers may also need longer to settle and mature. Some pubs have been known to keep very strong beers in a sealed cask for up to a year to allow them to fully develop.
When the landlord feels the beer has settled, and he is ready to serve it, he will knock a soft spile into the shive on the side of the cask. The major difference in appearance between a keg and a cask is the shive. A keg does not have a shive on the side. The majority of casks these days are metal, and at first glance look just like kegs. Even though there are still some wooden casks around, these are rare; in fact there are more plastic kegs around than wooden ones. Plastic casks are increasing in popularity because they are cheaper to buy and lighter to carry, though they don’t last as long. Beer casks come in a number of sizes, but by far the most common in the pub trade are those of 9 gallons (72 pints or roughly 41 litres) which is known as a Firkin and 18 gallons (144 pints or roughly 83 litres) known as a Kilderkin. (N.B. These are imperial gallons, equal to 1.201 US gallons each.)
The soft spile in the shive allows gas to vent off. This can be seen by the bubbles foaming around the spile. The landlord will periodically check the bubbles by wiping the spile clean and then watching to see how fast the bubbles reform. There still has to be some life in the beer otherwise it really will taste flat, but too much life and the beer will taste hard or fizzy. When the beer is judged to be ready, the landlord will replace the soft spile with a hard one (which doesn’t allow air in or gas out) and let the beer settle for 24 hours. He will also knock a tap into the end of the cask. This might simply be a tap if the cask is stored behind the bar. The beer will then be served simply under gravity pressure: turn on the tap, and the beer comes out. But if the cask is in the cellar, the beer needs to travel via tubes, or beer lines, and be pumped up to the bar area.
A “beer engine” or handpump is used to siphon the beer upstairs. The beer engine is a half-pint (sometimes a 1/4 pint), airtight piston chamber; pulling down on the handle raises the piston which drags up a half pint of beer. When a cask is first tapped into the beer engine, or after the lines have been washed through, the pump needs to be pulled several times to clear the lines of air or water. The line will continue to hold beer, which will tend to go stale overnight, so the first beer pulled through will be bad beer, and this will be simply thrown away. Most pubs will pull through at least a pint of beer on each beer engine before they open, while others will wait for the first order of beer on that pump before pulling through. Experienced barstaff will serve a pint with two long, smooth, slow pulls of the pump handle, plus a short third just to make sure the glass is full.
If you peek over the bar at the spout from which the beer emerges you may notice a small flip tap and a short spout; this is normal. If you notice the spout is quite long with a hairpin curve this is a swan-neck which is designed to force the beer into the glass, agitating it so that a head is created and some flavour is reduced.
In some pubs a small device or cap is fitted to the end of the spout rather like a sprinkler at the end of a hose pipe. The device is known as a "sparkler". Like the sprinkler at the end of a hose, this can be twisted to regulate the flow of the beer. When the sparkler is tight, the beer is severely agitated resulting in a large head but a significant loss of flavour and mouthfeel. This is most common in the North of England. Many drinkers in the North prefer their beer this way; it is softer and creamier with less bitterness. Drinkers in the South tend to prefer their beer with a touch more bitterness, and a slightly harder mouthfeel.
Those seeking authentic real ale should be aware that some pubs will disguise a keg beer by having some form of imitation pump handle on the bar. If the bar staff have merely turned on a tap, or are just resting their hand on a very small handle with no pump action, then this is a keg beer. Exceptions are some pubs in the North which use electric pumps or the few remaining pubs in Scotland that use traditional air-pressure founts on cask ale. Asking the staff will usually clarify this.
The famous warm temperature of cask beer in the summer months doesn’t apply all that often these days with temperature control units in pub cellars and the beer lines running through coolers. In fact, some pubs will run the cask ale lines through the lager chiller in order to get the beer below the maximum temperature required by Cask Marque, so a cask ale may end up as cold as a keg lager. This is rarely a good thing, because ale requires a cool rather than a cold temperature to reveal all its flavours. It can also disguise a far worse situation in which, although the beer in the glass is cold, the contents of the cask are rapidly turning to vinegar in the heat. Moderate cooling around the beer lines to maintain their temperature against the warmth of the bar is usually beneficial, but the beer must be stored at an appropriate temperature to begin with. In a well run pub the cask ale will be served at the appropriate temperature: cool, but not chilled.
The aroma of cask ale is fresher and more wholesome than keg beer. But the aroma of cask ale does not have the stored up impact of bottled beers; cask beer is beer which has already been exposed to the air for a couple of days, so there is not going to be a big impact when it is simply transferred to your glass. Typically the aroma will be released when it has warmed up slightly, and that will probably be when you are near the bottom of the glass. And no prickly oxygen tent aroma that comes with the extra CO2 used to give keg beer its “life”. All you will smell is natural, fresh beer—and the difference is like sniffing artificial fruit flavourings compared to sniffing the fresh fruit. The artificial flavourings will be pleasant and intense, while the fresh fruit will be very delicate, sometimes slipping away. Aroma, it has to be admitted, is not one of the high points of cask ale, but if you prefer scents that are delicate, exquisite, fresh and natural, then you will enjoy the bouquet of cask ale.
The flavour of cask ale is similar to the aroma in that it is delicate and fresh, but unlike many bottled beers the flavour of cask ale is more noticeable than the aroma. The aroma is often very slight, even non-existent at first, but the flavour makes up for that. Obviously the intensity of flavour depends on the beer style—a session bitter is not going to slap your taste buds in the way that a golden ale or imperial stout will—but a cask ale in good condition will have the flavours defined rather than muddled. CO2 bubbles in themselves have little flavour, so a mass of those bursting against your tongue will prevent the beer itself from making contact. With cask ale there is little carbonation, so more of the flavour compounds will be in contact with your taste buds. You should be able to clearly note the fruity sweetness up front, the balance in the middle and the bitterness in the finish. The flavour profile of a cask ale is much more noticeable than a keg or bottled beer.
The most important aspect of cask ale is the mouthfeel. It should not be fizzy. If your beer is fizzy then it’s either a keg beer or it’s a cask ale that’s been put on too soon. If you are used to carbonated drinks—keg beer, bottled beer, sparkling water, cola, etc.—the mouthfeel of a cask ale may seem a little strange—even flat or boring—at first. There are some people who don’t even notice the mouthfeel. If they are just drinking the beer without paying attention—maybe they are chatting away, or maybe they are trying to catch the aroma or flavour of this cask ale they have heard so much about—the mouthfeel will pass them by.