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Cask conditioning:

a do-it-yourself guide



This document was compiled by Gillian Grafton. No liability is accepted for the accuracy of the contents.

What is real ale? According CAMRA it is "a name for draught (or bottled) beer brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide." The essential points are secondary fermentation in the container from which it is dispensed (cask conditioning) and the method of dispense. So how do you achieve this at home? That's what this document attempts to describe.


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.

UK cask suppliers


Wooden Casks


The following extract is directly transcribed from H.E Wright's treatise on brewing (see sources cited at the end of this document). All emphasis is that of the original:

"Casks are made of foreign (Memel) oak, as a rule. The timber should be free from worm-holes and sap. It comes to hand in lengths (balk or juggle) of rather over six feet, and of a thickness which admits of three stave lengths being got. Foreign oak, being straighter in the grain than English, admits of being split; English has to be sawn. Moreover, the latter warps when steamed.

Barrel staves are 31 inches in length; kilderkin staves 25 inches, and care should be taken to divide the timber lengths so as to avoid waste. The pieces of which the heads are made are joined together by dowel pins (wooden pegs) and bevelled round, so as to fit into the croze grooves. The chamfered edges (afterwards painted) form the chime. The hoops of hogsheads and barrels are known as the end, bulge, and quarter hoops respectively; kilderkins (generally*) and firkins only have end and bulge hoops. Casks are classed as stout, intermediate, or slight, according to the thickness of the staves. The thickness of the heads and width of hoops also vary.

The thickness of the staves runs as follows.


                Stout.          Intermediate.   Slight.

                inches          inches          inch.

Hogsheads       1 1/2           1 1/4           1

Barrels         1 1/2           1 1/8           1

Kilderkins      1 1/4           1 1/8           1

Firkins         1 1/4           1 1/8           1


* Slight kilderkins, however are hooped with six hoops, like barrels."

After some discussion on the appropriate wages for coopers, Wright moves on to the treatment of new casks. This section is worth repeating in full in light of the often made assumption that casks imparted an oak flavour to the beer, which has led to many people incorporating oak chips into IPAs. Note that in his description of cask making, Wright does not mention lining the casks. This is a relatively modern phenomenom which has to do with cleanliness and not impartation of flavour. (Further discussion on lining casks can be found at the end of this section).

"To Season New Casks - Fill them with very hot liquor or salt. Most of the colouring matter and woody flavour will be extracted in thirty-six hours. Fill, however, for the first time, with black beer.

For pronounced "stinkers" there is supposed to be no cure, but the chloride of lime whitewash treatment, succeeded by muriatic acid and bi-sulphite successively, each being driven in by steam, might certainly be tried.

For moderate cases a foreign journal suggested treatment with strong solution of bi-carbonate of soda till it soaks into the pores. Then, after draining and rinsing, water acidulated with HCl is added, the evolved CO2 being supposed to drive out putrescent matter. The use of permanganate of potash has also met with some success."

It is also worth quoting a few of his words on cask-washing:

"Cask-washing Machines - The simplest form of effective arrangement for cask-washing (apart from taking out the heads of and hand-scrubbing each cask) is to have a series of nozzles, through which, by duplicate cocks, either steam or boiling water can be delivered. A modification is the Pontifex apparatus, where steam and water are admitted in a similar way, the water being boiled on its way, or within the cask.

Other machines have been designed to give a thorough revolving motion in all directions to the cask, which is charged with a few pebbles as well as half filled with boiling water. The most elaborate of these, which has not yet been surpassed, is the patent by Robinson of Bridgewater."

There is also an interesting discussion of wooden casks by Sykes and Ling in The Principles and Practice of Brewing, 1907, which is quoted in full here:

"The large vats for storing purposes are made of the best English oak, hooped with iron. Since they are subject to the attacks of a fungus which causes dry rot, they should be examined periodically, and measures for the eradication of the fungus taken as soon as its presence is detected.

The trade casks are generally made of foreign oak, occasionally of English. The best quality of foreign oak comes from Memel, the next best from Dantzic, other kinds from Odessa, Blumeza, and Riga. Ale casks have been constructed from time immemorial of wood, which is a substance of a porous nature, into the interstices of which bacterial and other minute organisms are extremely liable to effect an entrance. When certain species of these organisms have, in this way, invaded the substance of the wood, it is next to impossible to effect their removal. A cask so attacked is known as a "stinker," in which condition it is completely useless for the carriage of beer. On the Continent the casks are coated internally with a peculiar kind of pitch, so that the beer never comes into contact with the wood. Probably in the future some material which does not take up impurities so readily as wood will be employed in the construction of brewery casks, such as steel lined with tin, or wood with a lining of some indifferent metal."

So the conculsion from these two contemporary reports is that casks were made in the main from Memel oak, they were unlined (except in Continental Europe where they were lined with pitch), and they did not impart any oak flavour to the beer they contained. Thus the addition of oak chips or any form of oak flavouring to English styles of beers does not conform to the true style.




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.



UK beer engine suppliers


Sources Cited



*       Cellarmanship. Caring for Real Ale by P.J.O'Neill. Published by CAMRA. ISBN 1 85249 063 2. 2nd edition 1992.

*       Malting and Brewing Science. Volume 2. Hopped Wort and Beer (pp 687-692) by J.S. Hough, D.E. Briggs, R. Stevens, T.W. Young. Published by Chapman and Hall. ISBN 0 412 16590 2. 2nd edition 1982.

*       Brewing (pp225-227) by M.J.Lewis and T.W.Young. Published by Chapman and Hall. ISBN 0 412 26420 X. 1st edition 1995.

*       A Handy Book for Brewers being a Practical Guide to the Art of Brewing and Malting, Embracing the Conclusions of Modern Research which Bear Upon the Practice of Brewing, (pp 499-501) by H.E. Wright. Published by Crosby, Lockwood and Son, London. 2nd edition. 1897.

*       The Principles and Practice of Brewing (pp508-509) by W.J. Sykes and A.R. Ling. 3rd Edition, 1907. Published by Charles Griffin and Company Limited, London.

*       CAMRA fact sheet no. 3 "In the pub".



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This document is maintained by Gillian Grafton and was last updated on 1 May 1996. If you have any comments please advise her.



A version of this article first appeared in Brew Your Own magazine December 98.


Cask Conditioning Tips


The ins and outs of cask conditioned ale brewing and dispense were well covered in Brew Your OwnŐs May 97 issue and in the class handout for those alumni who attended more recent classes, so I will not dwell on the history, or the main brewing methods of the style. Instead I will attempt to provide a few hints on how to more closely replicate the British pub beer experience at home. The three day old, dried up, cheese and chutney sandwich youŐll have to manage on your own.




Farmers in England can still be persuaded to make the extra effort to grow top quality barley for brewing. British farmers work from a list of approved barley varieties and these varieties command a premium price over feed varieties. Barley varieties with exotic sounding names such as Maris Otter, Halcyon, Pipkin and, in Scotland, Golden Promise are as much a part of the recipe as a particular hop variety. They tend to be malted more slowly than American 2 row, resulting in less grain to grain variation. They are also kilned to a lower moisture content making them easier to mill with a 2 roller mill, easier to use in an infusion mash, less prone to sulphury flavors, stronger in flavour and darker in colour. As a commercial brewer, I have found that to get the best extract from an American 2 row malt you need a high mash temperature (156oF).  If you are using a single temperature infusion mash, then this precludes you from producing a highly fermentable wort and therefor a dry finishing beer. Using well-modified English malt will allow you to mash at a lower temperature, favoring fermentability, and still get a reasonably high extract. I have found that imported crystal malt seems to provide sweeter caramel flavors and colors with a reddish hue, compared to domestic caramel malt, which provides drier, spicier characters and a brown color. I have yet to brew with the new crystal malts from Great Western but the raw grains taste very good indeed.




British brewers use hops at a rate of about 1lb of medium a acid hops (4 -5%) per 43 gallon batch and mostly use whole flower hops. While the commercial English brewers have gone away from dry hopping over the years thereŐs no reason why American brewers need follow suit. Hops floating around the dispense container though, will seriously interfere with the dispense equipment, so containing the hop leaves in some kind of bag is recommended. DonŐt obsess too much about sterility when dry hopping, partly because you canŐt sterilize hops, but mainly because they act as their own preservative. It only takes about 7 days for a strong hop aroma to appear in the beer.




British brewers of cask beer have an advantage over their counterparts in this country in that they are able to devote an entire batch to cask conditioning rather than diverting a few kegs from a full batch destined to be filtered, carbonated and kegged. This makes it easier to arrest the fermentation with 1-2 specific gravity degrees still left and to remove the bulk of the yeast prior to conditioning. This means that American brewers will almost always have to prime their casks




A lot of articles on cask conditioning suggest adding a clarification aid such as isinglass as the beer is transferred to the cask. Commercial brewers in the UK now allow the yeast to remain in contact with the beer for the maturation phase and add finings only when the beer is required for shipping or dispense. This is because finings are very efficient at settling yeast to the bottom of the container and once there the yeast cannot do much fermenting. Some brewers even go to the trouble of rolling unfined, maturing casks in the warehouse occasionally, to keep yeast in suspension in contact with the beer. Cask beer is best drunk while it is young, but it should be easy enough to sample it regularly and judge for yourself.

Brewers who bottle condition already know that yeast, sealed up in a container with some sugars to ferment, will produce carbon dioxide gas. This gas cannot escape and so will dissolve in the beer causing the beer to become carbonated. The colder the beer the more CO2 will dissolve but since the gas comes from fermentation and ale yeast cannot ferment much below 50oF then there is a limit to the amount of carbonation that can be achieved without excessive pressure being generated.

Certain flavors, which may, or may not be appropriate in your beer, such as diacetyl (butterscotch flavor) or acetaldehyde (green apples) can only be removed by actively fermenting yeast. If the yeast is stuck on the bottom of the cask having been fined then it can do little to remove these flavors.

Since cask conditioned beer will be served without top pressure then only a low (0.9-1.2 volumes) level of carbonation is possible. That coupled with a slightly warmer serving temperature than keg beer, result in a greater perception of the multitude of flavors a cask beer can exhibit. Take into account using the flavorful barley varieties of English malt, dry hopping and natural clarification aided by finings, and you will see that the entire process is geared toward intensifying these flavors.




The original article on cask conditioning did, unfortunately, contain a mistake. In the chapter titled Fining the author states that finings aid in the removal of proteins. This is not the case as finings such as isinglass and gelatin are only capable of causing yeast to sediment out more rapidly. British brewers shouldnŐt have to worry too much about protein haze because British malt is low in protein and using kettle finings during the boil  helps dramatically. Commercial brewers in the U.K. use an auxilliary fining agent for protein removal. Beers served at Ňcellar temperature of 50oF are less likely to throw a Ňchill-haze.Ó The previous article also mentioned that isinglass is readily available and easy to use. Isinglass is very unstable at high temperatures and may lose all its activity if it is allowed to get too warm (over 70oF). It will also only clarify the beer up to 4 or 5 times, so if the fined beer is moved around too many times it will not clarify. It is also possible to overfine resulting in a sediment that floats up a little off the bottom of the dispense container, and the same effect can occur if the finings are not extremely well mixed with the beer. If your finings comes with instructions that tell you to add them to boiling water then you are using porkine gelatin as a clarification aid. This has been known to upset the occasional vegetarian cask beer enthusiast.




If you have fined the cask, and pressure has built up inside due to fermentation, the cask must be vented to atmospheric pressure before dispense. Do not suddenly release that pressure as the sediment will be roused up by the sudden release of gas and may not settle back down. If the sediment does get disturbed it is often a good idea to roll the cask, to remix the finings and yeast, and to allow it to completely resettle.

Some yeast can produce a lot of sulphur during the secondary fermentation, but that will collect in the headspace gas and can be vented away occasionally.

During dispense, if air is allowed to contact the beer then the container should be emptied in 2-3 days at the most. If you intend to keep the beer longer, then a blanket CO2 pressure (1Ú4 lb of pressure) will help preserve the beerŐs freshness. Oxidation causes a loss of fresh hop aroma and a souring of the beer. The beer should not have a hint of vinegar, although that is a common character in English pub beers particularly during the summer.

If you decide to purchase a beer engine or handpump as they are sometimes called, then there are a couple of things to remember. They are designed to pull beer out of the cask but offer no resistance to forward flow. Any pressure in the cask will force beer forward through the pump without pulling on the handle, resulting in a huge mess, and a loss of beer. If the beer is carbonated to around 1.8-2.0 volumes of CO2 then a sparkler attachment may be unnecessary. On most beer engines they are removable. Remember to rinse the pump out with water between tasting sessions, as beer left in the lines and pump can quickly ruin the system.