The Secrets of British Cask Conditioning

From brewing to serving, pros from the other side of the pond share some of the tricks of the cask-ale trade.

Bryan Betts Sep 5, 2017 - 11 min read

The Secrets of British Cask Conditioning Primary Image

“I can make your beer taste like shit,” grins Pub Manager and Cellarman Robbie Douglas, startling the group of foreign brewers touring his cellar. “But what you’ve got here is beer that’s well looked after,” reassures Douglas, who manages the grand Crosse Keys (cellar pictured above) in central London, a pub that sells 4,000–5,000 pints of cask ale a week.

Although good care at the pub is a vital part of the cask story—poor care in the pub can wipe out the brewer’s hard work—there is a lot more to it than that. Unless the beer is properly brewed and prepared for cask conditioning in the first place, even the best cellar manager will not be able to make it sing.

At the Brewery

The first step is to make sure there are fermentable sugars left in the beer when it goes into the cask, preferably by stopping the fermentation slightly early. “The fermentation proceeds until it is close to final gravity, and then the beer is chilled to arrest yeast activity. I allow the beer to chill to 8–10°C (46–50°F) and stabilize at that temperature for a day or two, then rack to cask,” says Tom Madeiros, who brews at Quercus Devon Ales in southwestern England.

Others work slightly differently. “The beer ends fermentation at about 20°C (68°F), and most yeast used for cask-only beer cannot quite ferment out completely,” says Dave Bailey of Hardknott Brewery in northern England. “The beer is then dropped to about 12°C (54°F), and the yeast goes dormant. The main point here is to consume diacetyl, hence the term ‘diacetyl rest.’ However, we still hope to retain some sugar.”


He adds that since he mainly produces keg and bottled beer, instead of cask-only yeast, he prefers an aggressive West Coast U.S. ale yeast that gets to the limit of attenuation very easily. “We drop out the yeast from the cone and dry hop. If we can then get the beer down to 1°C (34°F), so much the better; we also add a mineral-based finings adjunct to clear chill haze. After 3–5 days dry hopping, we then transfer to a bright tank, but without filtering.”

Once the beer is stabilized, brewers have another choice. Some will rack straight to cask while others prefer to part-condition in tanks. “Fuller’s has always done brewery conditioning. Before we had steel tanks installed in the 1970s, it was done in barrels,” says John Keeling, brewing director at London’s cask-focused Fuller’s Brewery. “Our beer was always two weeks old by the time it left the brewery. Some people think that’s cheating, but it’s not—adding CO2 and filtering, that would be cheating!”

He says that however you rack, the key is to “get your yeast count right. It doesn’t need a laboratory, just a microscope. If you have, say, a 5- or 10-barrel plant racking all to cask, first remove as much yeast as you can in the fermentation vessel. Then transfer the beer to a tank that can be roused, rouse it and measure the yeast count. If it’s 0.5 million cells per milliliter [ml] and you think it’s best at 1 ml, add more yeast. We leave ours in the rousing tank for a week—we do a lot of the secondary fermentation ourselves—it makes London Pride easier to look after.

“How long you need for your secondary fermentation depends on your yeast—how viable it is. Our yeast has been well trained for cask; it settles easily,” he continues. “You’re not doing a lot of processing with cask beer, so it’s more observing. A good brewer will get [a particular beer] right in three brews—the first not so good, the second not too bad, and the third spot on.”


The next element—assuming you want clear beer—is finings. “Auxiliary finings are added at chill if the beer is to be racked to cask directly from the fermentation vessel,” explains Quercus Devon Ales’ Tom Madeiros. “If the beer is to be transferred to a conditioning tank, the auxiliary finings can be added during the transfer. Alternatively, during racking into casks, the auxiliary finings can be added before the beer is put in the cask.”

How much fining agent do you add? This is where knowing your yeast count comes in, says John Keeling. “If we didn’t already know, we’d get advice from our finings supplier on how to get it down to 1 ml. For instance, we add three pints of finings per [288 pint]-barrel for 1 ml.”

He adds that Fuller’s controls its yeast count by centrifuging the beer and then reseeding with fresh yeast. Some other brewers argue that this breaks with tradition, but Keeling says it gives a more controlled process overall, adding that even with this and brewery conditioning, the beer will still condition in the pub cellar as well.

If the residual sugar level is too low, you can prime the casks, typically with liquid glucose. “We prime our casks—I can’t stand flat beer!” says Heather MacDonald, brewer at Scotland’s new Wooha Brewing Co. “We chill early instead [of priming], but priming is pretty common in British brewing to get a good secondary fermentation,” agrees Keeling.


MacDonald adds that while she has twenty-four casks, they are only for customers who can look after her beer properly—the rest of what she brews is bottle-conditioned. “I’ve been in too many pubs with badly kept cask beer,” she says. “No way am I putting all that energy in and having it go to waste!”

At the Pub

So how do you take care of cask? Keeping a clean cellar at 10–12°C (50–54°F) is the absolute top priority, brewers say, along with cleaning the pipes regularly—a big pub such as the Crosse Keys will have an automated system, cleaning four times a week.

“Have at least twice the amount of stillage space [a stillage is the device on which a cask is placed for use—e.g., a raised concrete area, a wooden or metal rack] as beers you want to serve at once, so four handpulls, eight stillage positions. Busy pubs might need more,” adds Dave Bailey. He continues, “Give the beer time to settle—if it is real cask beer, it will have sediment. Twenty-four hours [to settle] is quite normal, but don’t be surprised if it takes two to three days.”

Crosse Keys’s Robbie Douglas goes further: “We try to give everything four days,” he says. “Stronger beers [by British standards] at 5–6 percent ABV could use five [days]. To start with, we rest the cask for 24 hours after delivery to get its temperature stable. Then we roll it about vigorously [to rouse the yeast], put it on the stillage and vent and spile it. [A spile is a small wooden or cork peg for stopping a cask.] The beer drops bright in a day. That’s not condition though—for that it needs two or three days more for the secondary conditioning.”


It’s a little different with brewery-conditioned beer, according to John Keeling. “You can leave it on the cellar floor to condition, stillage it for 24 hours to settle, and then serve it,” he says. “We say don’t soft-spile because you lose gas. If you’re soft-spiling, it’s to allow gas out because the beer’s over-conditioned.”

He adds, “How long you leave it on the stillage will affect the flavor—there is a time when it’s just right. Taste it—is it fizzy enough? Leave it a day longer—is it better or worse? The whole reason that cask beer is so interesting is that it has these peaks and troughs. It’s why you can drink the same cask beer in two different pubs and find it tastes different—it’s all down to the publican and what the customers like: in one pub, [customers] might prefer it fresh; in the another they might prefer it a little older.”

Knowing which is which is the key, of course. While this ought to be simple, the reality is often sadly different. As Dave Bailey concludes, “The worst thing for a cask drinker is a barkeep who, when asked what a beer is like, replies, ‘Don’t know, don’t drink the stuff myself.’ Also, knowing the beers helps when someone complains. Bar staff who are unable to tell whether a beer is genuinely not right does not do the establishment, the brewer, or the beer any good. This applies to cask and keg—even keg can go wrong.”

How Much Does Cask Waste?

One of the arguments sometimes used against cask is that it results in waste. That’s because no matter how well you look after the beer, you have to throw some away with the yeast that settles to the bottom, into the belly of the cask. Along with wastage from line cleaning, sampling and so on, the rule of thumb is you can expect a 72-pint firkin to yield only 66 drinkable pints.

Tilt the cask to get more out at the end, and you risk stirring up the sediment—and hardly anyone wants the resulting murky pint and the upset stomach he/she fears it will bring! Pubs get around this problem by using auto-tilts, which gradually and gently tip the cask as it empties and lightens, leaving as little as 2 pints of sediment remaining.

Go beyond smack packs and yeast starters with Craft Beer & Brewing’s online class: Advanced Yeast Management.