Serving Cask Ale

Cellar Temperature

It is important that cask ale be served at cellar temperature. This is 48 – 54°F (9-12°C), the average year-round temperature variation of a below-ground cellar. Proper cellar temperature allows for the appropriate levels of dissolved CO2 to be maintained. As we saw in the table from Chapter 2, reprinted below, cellar temperature allows for the beer to naturally hold on to 1.1 to 1.2 dissolved volumes of CO2. As the beer approaches room temperature, its ability to hold on to CO2 diminishes rapidly.

Dissolved Volumes of CO2 Present after Fermentation

Temperature (°F/°C)	Volumes CO2
47 °F (8.33 °C)	1.21
50 °F (10.0 °C)	1.15
53 °F (11.7 °C)	1.09
56 °F (13.3 °C)	1.04
59 °F (15.0 °C)	0.99
62 °F (16.7 °C)	0.94
65 °F (18.3 °C)	0.89
68 °F (20.0 °C)	0.85
71 °F (21.7 °C)	0.81
74 °F (23.3 °C)	0.77
77 °F (25.0 °C)	0.73
80 °F (26.7 °C)	0.69
83 °F (28.3 °C)	0.66

While most bars or event spaces lack an actual cellar to store casks in, other strategies can be adopted to keep the beer at the proper temperature. These will be discussed in the various service situations that follow.

Maintaining the CO2 levels has an important impact on the flavor of the beer. Without the higher carbonation levels found in kegged beer, the hop aromas of the beer are not lifted to the nose as readily. This is not to say that cask ale is doomed to have low hop character, just that relying on the CO2 to lift the aromas is a poor strategy. There is also reduced tingling sensation on the palate. If served above cellar temperature, the beer will quickly lose all dissolved CO2, to the detriment of the flavor. Warm and flat is not an acceptable way to serve cask ale.

As mentioned previously, beer served ice cold actually numbs the tongue, muting the flavors of the beer. Serving at cellar temperature allows for more of the flavors in the beer to be tasted as the beer is consumed. The reduced CO2 levels, as noted above, results in a reduced carbonic acid component, making cask ale taste slightly sweeter than its kegged counterpart. This places an emphasis on the malt character of beer.

Brewers making cask ale recognize the impacts of the service conditions and can brew their beer to take advantage of this situation. In England, the task of bringing out the best of what they brew is delegated to the cellarmen. There is no tradition of trained cellarmen in America. Hopefully this text along with Patrick O’Neill’s excellent ‘Cellarmanship’ will help fill this gap.

Venting and Tapping

With the cask loaded onto a stillage and resting at cellar temperature, it is now time to vent and tap the cask. The basic idea is really simple – you’re creating a hole in the top to vent excess condition, then punching in a tap for service later. The tools themselves are also simple.

Hard Spiles

Useful in venting and sealing the vessel. Use the wooden ones, not the plastic ones.

Soft Spiles

Porous to allow excess condition to pass through. Some use it as a coarse filter while drawing beer.

Venting Tool

For the faint of heart that won’t vent with a hard spile, this is the tool for you. Very useful with overcarbonated American casks.

Gravity Tap AKA The Filton Direct Dispense Tap

This is THE tap for serving ales straight from the cask. Simple design, durable construction.

A venting tool is a simple way to control the release of the trapped gas within the cask. Be sure to sanitize the shive and the venting tool.  Check that the valve on the venting tool is in the closed position. Hold the venting tool over the shive and knock it in with one sharp blow. Then, with the tubing safely directing possible exhaust into a container, slowly open the valve and vent the gas and foam from the vessel. If it is highly over-carbonated or infected, CO2 can migrate out of solution and keep venting out the venting tool for an extended period of time.

Without a venting tool, a cask can still be vented using only a hard spile. It has a potential to make an impressive visual display if there is significant condition to vent. The only advice that can be given is to rock the hard spile gently to work it back out and listen to the venting. When the pitch falls, resume working the spile out until it can be removed in its entirety. If there is still a lot of foam rising, a soft spile can keep it in while venting the excess carbonation.

Tapping is perhaps the most fun one can have with beer. The principle is really simple: drive the tap into the keyhole. There is some question as to whether or not to have the spile in or not when venting. Leaving the spile in conserves what condition is in the beer. It also traps what condition might get knocked out of solution, causing a spike in pressure within the cask. This could cause a catastrophic failure of the spile, making for an exciting beer fountain. Taking the spile out and knocking the tap in could cause the same condition to be knocked out of solution, where it is lost. There is therefore a danger of causing the beer to be underconditioned before it even has a chance to be checked.

Clarity

Because cask ale is unfiltered, there will inevitably be some yeast in solution when the cask is filled. Brewers may also add dry hops or other spices directly to the vessel. There may also be brewing artifacts such as protein clumps in the mix. None of these are attractive in the poured pint. This section will mention a few strategies to reduce or eliminate these common causes of cloudy beer. There will be further discussion on these strategies in the appropriate circumstance of their use later in this text.

The goal of every cellarman should be to serve the beer in the best possible condition. For this cellarman, that includes taking reasonable steps to make the beer as bright (brilliantly transparent) as possible. Eliminating discrete bits is an obvious first step in this process. Reducing or eliminating yeast in suspension is the next. While certain styles and breweries rely on the suspended yeast as part of their flavor profile, the vast majority do not, as evidenced by the filtering of their bottled beers. It is left to the cellarman to present the beer in the best possible light not only to make the brewery look good, but to reflect the standards of the house and encourage repeat business by building a reputation of excellent cask ale.

Bright beer begins at the brewery. The brewer must do a good job of complete starch conversion in the mash and have adequate hot and cold breaks for protein removal to have any chance of bright beer. Some styles such as wheat or wit beers will never be bright. The recent trend of extremely hoppy beers has introduced the challenge of hop protein haze. Keeping the yeast healthy throughout fermentation is also important. Filling the casks using good sanitary practices is vital to lessen the possibility of introducing contaminants such as wild yeasts or bacteria. In the UK it is common for the brewer to add a fining agent such as isinglass to the beer to help settle the yeast. A more recent trend has been to add Alginex (a polysaccharide-based auxiliary fining with strong negatively charged molecules) in conjunction with isinglass.

Isinglass offends some people as it is derived from the swim bladders of fish. Recently a purified colloidal solution of silicic acid (SiO2) called BioFine CL (Clear) has been introduced to the market. It acts in much the same was as isinglass and is slowly starting to replace isinglass in the industry.

The cellarman can act prophylactically when preparing beer for service by dosing it with finings before it is loaded on the stillage. They can be reactive and work with the beer on the stillage. Coarse physical filters can be used to hold back floaty bits. There are a variety of other strategies to encourage beer to drop bright that will be discussed in due course.

Flavor Evaluation

The cellarman is the last link in a chain of beer production that starts with the farmer. While he or she has no control over the quality of the beer in the cask, an inattentive cellarman can turn the best beer in the world into a cloudy swill unworthy of supping. Tasting the beer before service is a critical step in serving quality cask ale. The presence of live yeast allows the flavor to evolve once stillaged, vented, and tapped.

Flavor evaluation is quite different from deciding if one likes the beer. The brewer makes the beer and it is what it is. The cellarman, in trying to serve the best beer possible, is looking for specific developments as the flavor evolves. Here are a few easily identifiable off flavors:

Acetaldehyde is a green apple flavor. It is an indicator the the beer is ‘green’, freshly tapped and young. It is typically reabsorbed by the yeast in a day or so once the carbonic acid levels are reduced by venting. In high levels, the presence of acetaldehyde could be the result of too-high storage temperatures.

Thin or sharp mouthfeel is an indication of excessive carbonic acid. These levels are typically reduced by venting. The flavor should fill out a little after a day or so, especially if the carbonation levels warrant use of a soft spile.

Vinegar or salad dressing flavors are a very bad sign. They usually indicate infection by a spoilage organism. Waiting a day will confirm this suspicion as it only gets worse. This is not to be confused with deliberately soured beer.

Sour flavors appropriate for the style. Americans have seen a rise in just about anything in casks. As someone who is not a fan of sour beer, the author was pleasantly surprised by how nice a berlinerweiss could be on cask. Besides the obvious sours, other styles such as old ale or barleywine could have this as part of their flavor profile.

Diacetyl is a very familiar flavor compound associated with buttered movie theatre popcorn. It is usually produced by unhappy yeast. Fortunately it is quite volatile and can evaporate through the spile hole if left open. If it intensifies, this indicates an active fermentation or contaminant working the beer.

Sulphur can come from a variety of sources. Some waters, typically in Wales, are naturally high in sulphur and inadequate venting of the boil can intensify them. Allowing the beer to age a bit on the stillage seems to reduce the perception via oxidation or palette acclimation.

DMS, dimethyl sulfide, is that vegetal / creamed corn flavor. It is typically produced by the yeast from a precursor compound (SMM, S-Methyl Methionine) naturally found in malt and typically removed by a vigorous boil. There’s not much one can do except remove the beer from service if you determine it to bee too detrimental to the flavor of the beer.

Oxidation is that wet paper or cardboard flavor. While this is typically a fault if found in a bottled beer, in a cask ale it is an interesting flavor contributor to be monitored. Because the cask is open to atmospheric oxygen, there will inevitably be some flavor oxidation. This isn’t necessarily a bad thing. The effects are somewhat mitigated by the geometry of the vessel and the logistics of service. While beer flows from the bottom of the cask, atmosphere is pulled in at the top, albeit gently. Inside the cask there isn’t much motion so mixing is just via diffusion. There is still carbon dioxide coming out of solution, reducing contact at the surface of the beer. Even if oxygen gets to that liquid surface, there isn’t much motion to encourage mixing within the liquid portion of the cask either. While the very top layer may oxidize quickly, the main body does so much more slowly. Even when it does, the living yeast interact with the dissolved oxygen and the oxidized compounds. Suffice it to say, there is a lot going on. It is this slow oxidation that contributes to the flavor evolution causing most beer to peak in flavor on the second or third day of service.

To be clear, too much oxidation is a very bad thing. A bitter or an IPA probably won’t last much beyond its peak and declines pretty quickly once it reaches that peak. On the other hand, some beer, such as a heavy stout or barleywine, may be able to stand up to the oxidation for quite a long time. If the beer tastes old or tired, it’s time to remove it from service.

Tasting the beer is all about decision-making. The descriptions above are just to inform the cellarman so that he or she can make their own best decisions. Beer that is bad should never be served. This may mean pulling a vessel from service when there is half or more of the cask remaining. Additional tools such as a microscope might give confirmation of contamination or prove that yeast is the source of a haze. Taste the beer and make the decision.