Cask Conditioning

Casks are traditionally made from European oak or more commonly nowadays from stainless steel or aluminium. They have an opening at the front (approximately 25 mm diameter) for attachment of a tap and a second opening (shive hole) at the top (approximately 50 mm diameter) through which the beer is racked into the cask. The front opening is stopped with a wooden or plastic plug (the keystone). Similarly, the shive hole is plugged with a shive. Both keystone and shive contain central knockout sections. The cask also comes with a hard peg known as a hard spile and a soft peg known as a soft spile. Traditional cask sizes are derived from the 36 gallon barrel. They are:

    4.5 gallons - Pin
    9 gallons - Firkin
   18 gallons - Kilderkin (Kil or Kiln)
   27 gallons - Half-hogshead
   36 gallons - Barrel
   54 gallons - Hogshead

The term conditioning covers all of the changes that occur in the beer from the time it is primed to the time it is served. It should not be confused with the condition in the beer which specifically refers to the amount of carbon dioxide in the beer.

Cask conditioned beer must be set up in its serving position and then left undisturbed until the cask is empty. Support the cask on three points only, two at the front and one at the rear. A permanent storage system, known as the stillage (also known as the stillion, horsing, or thrawlls, and in Scotland as the gauntry) can be constructed by laying two horizontal beams and by fixing onto the rear beam cut-out circular blocks with a radius less than that of the cask, so that the cask is tilted forwards towards the tap. Put the cask onto the stillage the moment the beer is racked into the cask.

Once the primary fermentation has been completed, the beer is racked to the cask. Traditionally this is done when the beer is two degrees above its final gravity. There should be sufficient residual sugars in the beer to allow secondary fermentation to occur. However, many brewers add priming sugar when the beer is racked to the cask. Dry hops and finings (approximately 1 pint of isinglass per 9 gallons of beer) are also added at this stage. The cask is now closed with the shive and left for several days before venting (spiling). To vent the cask the centre of the shive must be driven into the cask. The simplest tool to do this is a hardened steel punch. Punch through the knockout section and immediately insert the soft spile. Spiling can be spectacular, if pressure has built up hops and beer can spray up in fountain. In practice little beer is lost despite how it looks. The spile must be checked every day to ensure that it is not blocked with hops or saturated with yeast. The beer should now be allowed to mature and come into condition. The time required is highly variable ranging from several months for strong ales and barley wines to less than a week for low gravity beers such as milds and light bitters. As soon as evolution of gas from the cask has ceased, the soft spile must be replaced with a hard spile.

A word of explanation is needed here. This system evolved way before the invention of pressure regulators. Secondary fermentation of the beer in a closed cask ensures that the beer becomes completely saturated with CO2. The soft spile is made of porous wood and can allow exchange of gases between the cask and the outside world. At this point the beer is still evolving CO2 so no air enters the cask. The soft spile serves to ensure that the beer does not become overcarbonated. Once CO2 evolution has ceased air could enter the cask so at this point the soft spile is replaced with the hard spile. The whole system serves to ensure that the beer achieves perfect condition. This is defined as the situation in which the beer contains 1 volume of CO2 per volume of beer (ie. the partial pressure of the CO2 in the beer is 1 atmosphere).

Insertion of a tap (tapping the cask) can be done at several points, either when the cask is spiled, a day or so before use, or just before it is required. There is no particular advantage to one time point over another. To tap the cask, first remove the spile, then drive the tap through the centre of the keystone using the heaviest mallet you can find (at least 1 pound in weight - never use a metal hammer, it will damage the tap). Some cellar keepers leave the tap partly open whilst driving it through the keystone. Ostensibly this ensures that air is not driven into the cask, but it is questionable whether this is of benefit. Some sediment will deposit itself in the tap, so the first 1/3 pint or so will be cloudy and must be discarded. The beer lines (if used) may now be attached to the tap and the spile must be re-inserted. Occassionally it may be necessary to replace the tap on a full cask, usually the cause is a leaking tap. This isn't the disaster it may appear. First insert the hard spile into the cask, this produces an air lock so that little beer will escape the cask. Gently rock the tap whilst holding it into the keystone. You will feel the tap coming loose. Hold the tap in the keystone, take a cork bung and hold it next to the keystone. Pull the tap out and quickly insert the cork bung. Drive the replacement tap through the corked keystone in the usual manner.

When beer is served the hard spile must be completely removed from the cask to allow air to enter the cask replacing beer which has been drawn off. If the spile is left in, the beer will not be able to be pumped. Replace the spile when the cask is not in use. After a cask is vented and entered into service air will enter the cask causing oxidation of the beer, and dissolved carbon dioxide will be lost through the exposed surface of the beer. Good cellar practices will minimise these effects, but it should be remembered that the effects are part of the traditional profile of real ale.

Finings are normally added when the beer is racked to the cask. Sometimes, if the beer will not drop bright, it may be necessary to re-fine. The complete shive must be removed with a de-shiving tool. Pour in the finings and insert a new shive. Roll the cask vigorously to mix the beer with the finings. Re-spile the cask immediately. The finings initially flocculate into loose lumps which gradually accumulate into bands alternating with bright beer. These bands then move to the top or bottom of the beer (the top break and the bottom break). Occassionally you will get banding or layering in which the sediment will accumulate in the middle of the beer. Beer above and below the band will be perfectly bright. Nothing can be done about this, the cloudy beer must be drawn off and discarded.

The temperature of the beer is an important aspect of real ale. The cellar should be maintained at 13-14 C (55-57 F). The temperature affects the condition of the beer and also the clarity since isinglass finings are rendered useless at high temperatures. Too warm and the beer will be flat, too cold and it will be over gassy. Real ale in perfect condition contains one volume of carbon dioxide per volume of beer. Top-pressure is often employed by homebrewer, this is the application of carbon dioxide at relatively high pressure into the beer. This makes cask beer greatly over conditioned. The resulting beer cannot be considered to be real ale. Blanket pressure may be applied to real ale if the turnover of the beer is low. In this system a demand valve allows carbon dioxide to be drawn into the cask as beer is drawn off, and thus air never enters. A secondary relief valve must be included to automatically vent a build up of pressure (above 1 atmosphere). There is a rift in the real ale world as to whether beer served under blanket pressure can be described as real ale, but in practice it can allow homebrewers to enjoy real ale without having to worry about spoilage of their beer.

Dispensing

Gravity Dispense

    This is the simplest method of all. Simply tap the cask and allow the beer to flow freely into your glass. The cask must be vented to allow air to enter to replace the dispensed beer. You will not get a head on your beer using this method so it is particularly suited to Southern type beers (see below).

Air Pressure

    This system is almost exclusive to Scotland where it is the predominant traditional method. Simply put, pressurised air is used to force the beer up to counter dispensers. Oxidation is not noticeably increased by this method but there is a small increase in the condition of the beer. A home system might easily be made using a small air compressor - but be very careful that it is suitable for use with foodstuffs!

Beer Engine

    This is the correct term for the device commonly seen in British pubs which pumps beer from the cask to the bar. Also known as a handpump or beer pump.

    It can't be emphasised enough that you should use the correct beer engine for the style of beer. Beer engines have two styles of neck, the swan neck and standard neck. Swan necks do untold damage to beers with a flowery hoppy aroma knocking the aroma out of the beer. The second feature which affects the beer is the sparkler. Sparklers force the beer through many small orifices producing a tight frothy head on the beer. Northern style beers (eg Tetley) should be dispensed through beer engines with a swan neck using a sparkler and produce an excellent pint that way. Southern style beers (eg Fuller's London Pride) should NOT be dispensed via a swan neck and certainly not through a sparkler. The result of this is of course, that Southern beers are not served with a head. Southern beers served in the northern manner are lifeless travesties of beers, whilst served in the proper manner they are a revelation, a wholly different beer. So the moral is get the beer engine appropriate to the style of beer you have brewed.