THOUGHT PIECE the carling team

Back To The Pub – Getting The Perfect Pint Of Cask Ale

Cask beer is not chill proofed by brewery conditioning nor is it filtered or pasteurised so there are both haze and infection risks unless good pub practice is rigorously followed. To recap, you package the beer into a cask straight after primary fermentation with enough sugar to promote a secondary fermentation which encourages the remaining yeast to remove ‘green’ flavours and build up carbon dioxide.

Isinglass finings settles the yeast into the belly of the cask and the very slightly fizzy (around 1.1vols or 2g/L CO2) bright beer is pumped to the bar for sale. Isinglass is a collagen preparation made from the swim bladders of various warm water fish. These are sun dried and those which do not end up as Chinese fish maws soup can be treated with dilute acid (once tartaric but now usually phosphoric) which teases the long triple helix collagen molecules apart. Isinglass has an overall positive electrostatic charge which attracts yeast cells.

Hogsheads (54 gallon casks) are rare these days

Marstons has patented its Fast Cask technique, which involves a specially prepared yeast, so that fast-clarifying cask beer would allow it into outlets without proper cellar facilities. A two stage process sees yeast cells immobilised with alginate and then encapsulated in a permeable alginate matrix. With a particle size of around 1mm, they settle to the bottom in 20 seconds and no finings is needed. The yeast maintains the CO2 content which was present at packaging. Pubs can get a couple more pints out of each cask and Marstons say there is no discernible difference from traditionally prepared and cellared cask beer.

The naming of parts for traditional belly dispense

In the pub, ordering the correct cask size for your projected sales over the week is paramount. As soon as dispense starts, cellar air is drawn inside. This will not be sterile and the oxygen will affect beer flavour either directly or via yeast metabolism. As the level in the cask drops, the surface area to the volume remaining increases dramatically. If sale is slow, this surface develops taints and as it reaches the tap, the deterioration will be very apparent in the glass. Ideally a cask size should be chosen which will empty completely in 48 hours or 72 at the very most. Sadly few brewers provide 4.5 gallon pins, the next smallest size. The excuse seems to be that unless a deposit is charged on the container, these are highly prized by the home brewing fraternity. Unless you can find a brewer offering pins, a firkin (9 gallons) of each brand on sale must be sold within three days. It is better to withhold slower selling products until the busier weekend trading or if possible mix container sizes rather than risk substandard beer.

The cellar cooling fan (top) and below vertical dispense and Flojet pumps to push the beer to the bar

It is possible to get around the problem of drawing contaminating air into the cask by fitting a demand valve (aka aspirator or cask breather) which introduces a volume of inert nitrogen or CO2 at ambient pressure to match the beer volume leaving. Some commentators seem to suggest that the use of a demand valve is somehow an excuse for being unable to get your cask stock control correct. They worry that casks will be on sale for weeks and go beyond the best before date with the development of aged flavours. As a dedicated cask drinker I would prefer to be assured of the quality of the last few pints out, if I happen to get one of them, than worry about the logistics capabilities of the licensee!

The beer cellar is absolutely key to successful cask beer dispense and the temperature should be kept at 12oC. A classic stillage for casks would have been a raised plinth and scotches (triangular pieces of timber) are used to wedge the casks in a horizontal position. Smaller casks can now be stored on racks some with mechanical handling hoists and fitted with springs so that the back of the cask is tilted automatically as the volume inside it decreases. Without these auto tilting mechanisms, casks need to be stooped forward when they are no less than two thirds full to allow a maximum volume to be drawn from them. About 12o from the horizontal should be sufficient and will leave a sediment of around 1.5 litres in an 18 gallon cask.



After delivery the casks should be left for twenty four hours while they reach cellar temperature and the sediment drops into the belly. Both shive and keystone apertures should be clean and rinsed if necessary. A tap is driven into the keystone and the cask inspected for ‘condition’ (liveliness) by knocking the plastic tut through the shive while having a soft peg handy. This bamboo or porous soft wood peg or spile allows the accumulated carbon dioxide complete with unwanted green beer aromas to escape. If the beer is lively the soft peg will allow continuing evolution of gas as the beer conditions. It should be replaced at least daily to avoid the pores blocking. Once the cask has quietened down, a hard peg is inserted to maintain the condition (CO2 content) until the cask is put on sale.

The long extractor tube(left) is easily knocked. The Cask Widge has a flexible tube with take off float just below the beer surface. Do not mix up the firkin tube in blue with the kil tube in red! On the right is Mason’s float device. Note the flow meters on the beer lines

This hard spile needs to be removed at the start of a serving session and replaced firmly to prevent undue loss of carbonation overnight. You can buy controlled vent pegs with a side valve which is manually snifted or go the whole hog and use an automatic spile like the Race ventilator where an outlet valve will allow the cask to ‘work’ and a separate inlet will allow air in once dispense is underway.

It is possible to set the cask in a vertical position for dispense through the keystone (tap) aperture using an extractor tube. This saves on cellar space and as the bottom of the tube can be positioned anywhere in the cask and clamped, it is possible to serve clear beer from the top layers before the entire cask has dropped bright. The extractor finishes with a screw- on plastic ferrule which is drilled around 4mm from the end to keep the beer flow away from the sediment. To maximise yield, a small wedge is placed to tilt the cask very slightly to encourage the sediment to drop away from the bottom of the tube. This is gently removed when the cask is put on sale.

Detractors say trying to serve beer too early will yield green flavours in the glass, the unit can easily be knocked and has to be cleaned by the cellarman. With its lengthy tube, there are risks that this operation will not be carried out rigorously even if the cellar has a specially made metre long cleaning trough and a very long thin brush.

An ale python controller has a water bath set at around 8 degrees Celsius. Beer mains run close to the chilled water pipes which also feed jackets around the pump cylinders

An alternative to the extractor, although it still needs local cleaning, is the Cask Widge. Made of plastic, this device is pushed into the keystone aperture. The beer can be conditioned using a control venting valve and an inserted soft peg. When the beer is ready for sale a flexible tube finishing with a float and specific for the size of cask in use is fed through the hole and sealed in the housing. The main drawback of this device comes when the cask is almost empty and there is loose sediment which the float can settle into and pass cloudy beer to the bar thus necessitating a line clean before another cask can be put on sale.

A couple of final cautions while we are still in the cellar. Clean the lines at least once a week, while some cellarmen will clean as soon as one cask is finished this will delay getting another beer on sale considerably. Finally make sure that once a cask is empty that the peg is driven right into the shive and a cork put in the keystone. Casks easily dry out in hot summer months a long way from home which makes washing a lot more difficult.


The beer is cellared at 12oC, the ideal cask drinking temperature is 12oC but unless your bar is kept at 12oC the beer will warm up. Traditionally there was a short run from the cellar directly below the bar and sales were brisk, today with pubs open all day, a mid afternoon pint can be unacceptably warm. Beer is now pushed to the dispense point using positive displacement Flojet pumps through 3/8” o.d. tube (16m to hold a pint) as against the old 5/8” tube which held a pint in every three metres. It is no solution to run the cask pipes on the outside of the lager tubes within a single python since at times of low trading the pint will be unacceptably cold. A dedicated ale python is ideal, where coolant is fed from a water reservoir kept between 7-9oC. The beer lines surround the flow and return coolant which is also connected to jackets around the beer engine cylinders.

A saddle cooler and an internal coil to keep beer cool if not in a cellar

Nothing is simpler than sitting a cask behind the bar and dispensing directly from a tap into a glass or jug. However keeping the cask cool becomes even more of a challenge. The use of a wet piece of sacking does not look very professional. Casks can be kept cool using a saddle of cooling tubes shaped to rest on the top surface of the cask and covering it with an insulating jacket. Water is circulated from an ice bank cooler. An alternative would be to insert a cooling immersion coil through the shive hole, the seal allows circulation of coolant as well as peg venting of the contents. Again an insulating jacket is essential.


Below the bar, the mechanism of an Angram CQ hand pump

The beer engine on the bar is always a good sign that a pub has cask conditioned beer though the unscrupulous have been known to activate a micro-switch as the tap handle is moved and introduce beer from a keg into the glass! There are cylinderless units on the market which are damped to feel like the real thing and rely on the cellar gas pump to maintain the flow. In a classic pump the downward movement of the tap handle operates a quadrant lever which will pull a cylinder spindle and its piston upwards pushing beer towards the bar and at the same time allowing beer to flow in below. Returning the handle to the vertical position opens a non-return valve and the beer below the piston passes through waiting for the next pull. The tap is now finished with a swans neck (complete with a sparkler) so that it can be positioned right at the bottom of the glass being filled. The flow of beer under pressure through orifices in the sparkler will increase the speed allowing gas breakout to create a head on the beer.

Did you miss this during lockdown?

Towards the perfect pint of cask ale; train your staff, always have someone on duty who knows about beer in general and the casks on sale in particular. Be prepared to accept higher wastage than on a keg lager and do not try to sell anything towards the bottom of a cask which you would not drink yourself. Do not overextend the range of cask beers on sale and keep rigorously to the absolute maximum of 72 hours on sale rule. Stock a balanced mix over the range with familiar and less well known brands, local and exotic, faraway beers with a mix of style, colour and %ABV. Sell flights of samplers and let unfamiliar customers ‘try before you buy’. Have a prominent blackboard showing the main characteristics of each beer on sale. Promote your range on social media, try regular beer and food matching events and ‘meet the brewer’ sessions. You may not push back the tide of international lager brands but with 3018 brewers in the country and most of them only making cask ale, the pub sector is at least more interesting than it was.