Cask Ale vs Keg Beer: What Changes at the Bar?

Cask ale vs keg beer: what is the short answer?

Cask ale is beer that finishes maturing in the container it is served from: it still holds live yeast, it is vented so it pours at atmospheric pressure, and it reaches the bar by hand pump or straight from the barrel. Keg beer is finished at the brewery, usually filtered, and pushed to the tap by gas. Cask pours softer and at cool cellar temperature; keg pours colder and fizzier. Neither is automatically the better pint. They are two different ways of getting beer into a glass, and each one rewards different things.

What actually is cask ale?

The working definition comes from the Campaign for Real Ale (CAMRA), the consumer group that has argued for traditional British beer since the early 1970s. When it updated its terminology in 2021, CAMRA described cask-conditioned beer as "live beer that continues to mature and condition in its cask", with "any excess of carbon dioxide being vented such that it is served at atmospheric pressure".

"Live beer" is the important phrase. CAMRA defines it as beer that, when first put into its final container, "contains at least 0.1 million cells of live yeast per millilitre", plus enough fermentable sugar to keep fermenting in that container. In plain terms, the brewery sends out beer that is not quite finished. The yeast keeps working in the pub cellar, producing a gentle carbonation of its own; this is called secondary fermentation, and the process of letting it happen is called conditioning.

That is why cask ale asks so much of the pub. The brewer Adnams advises publicans to tap a cask 24 to 36 hours before serving it "to allow the sediment to resettle", and recommends soft spiles (porous pegs) to let excess carbon dioxide escape, swapped for hard spiles to seal the cask at the end of service. CAMRA's 2021 note says cask beer may need to settle and condition in the cellar for up to ten days.

What is keg beer?

Keg beer leaves the brewery finished. It travels in a sealed container and is dispensed by gas, so the pub's job is to keep it cold and the lines clean rather than to bring it into condition. The word covers two quite different products.

Traditional keg is the beer CAMRA was founded to resist. A CAMRA Technical Advisory Group piece republished by its Greater Manchester branch records that "When CAMRA was established in 1971 it fought against the sweeping trend" for cask-conditioned beers to be replaced by keg, and describes those keg beers as "usually filtered and often even pasteurised", with carbonation added back afterwards. CAMRA's Lincoln branch explains that traditional keg is "chilled and filtered to remove all the yeast", heat-treated, and that carbon dioxide "has to be added to make the beer fizzy".

Craft keg is the newer style you will find on many modern bar fonts. The same Lincoln CAMRA piece describes it as filtered only lightly, without pasteurisation, with its carbon dioxide arising naturally from fermentation, though gas is still needed to get it from the keg into the glass.

There is a third case that blurs the line. Membrane kegs, often called by the brand name KeyKeg, hold the beer in a sealed bag inside a rigid outer shell; gas squeezes the bag rather than touching the beer. The Greater Manchester CAMRA article calls this "a flexi-walled cask that shrinks as the beer leaves it", and records that CAMRA accepted such kegs can contain real ale, on the condition that it is labelled as such.

Is "real ale" the same thing as cask ale?

Nearly, but not exactly. "Real ale" is CAMRA's term, coined in the 1970s. The definition CAMRA adopted in its early days, quoted in its 2021 update, is the Oxford English Dictionary's: "Cask-conditioned beer that is served traditionally, without additional gas pressure". CAMRA also recognises bottle-conditioned beer as "real ale in a bottle", and, as above, live beer in a membrane keg.

So at the bar, "real ale" nearly always means the cask beers on the hand pumps. One more wrinkle is the cask breather. This device, as Wikipedia's real ale entry describes it, "adds low pressure carbon dioxide into the cask to replace the beer as it is drawn off". CAMRA did not count cask-breathered ale as real ale until it changed that policy in 2018.

How is each one served at the bar?

Cask ale usually comes through a tall hand pump, properly called a beer engine. Wikipedia's beer engine entry calls it "a device for pumping beer from a cask", normally worked by hand, which draws the beer up from the cellar. The other traditional method is gravity dispense: the cask sits on a stillage (a cradle or rack) behind the bar or at a festival, and the beer is poured straight from a tap in the barrel. Either way, as Wikipedia's real ale entry puts it, "No external pressurization is used."

Keg beer comes from a font: a fixed tap, often a branded tower or a row of plain taps on a backboard, which opens and lets gas pressure do the work. A rule of thumb for most British pubs: a handle you pull is cask; a tap you open is keg.

Why does cask ale feel less fizzy?

Because it is. The Greater Manchester CAMRA article puts the norm for cask-conditioned ales at "1.1 volumes of carbon dioxide in every volume of beer". That carbonation comes from the yeast's own secondary fermentation, and venting the cask lets the excess escape until the beer sits at atmospheric pressure.

Keg beer is carbonated to a level the brewer chooses and held there by gas in a sealed system, so it reaches the glass livelier and keeps its sparkle for longer.

The practical effect at the bar is texture. Great Newsome Brewery, a cask brewer, describes cask's appeal as "a much smoother mouthfeel compared to something like a carbonated keg". A cask bitter tends to feel round and soft; a keg pint feels brisker, with more bite from the bubbles. Neither is a fault.

What temperature should each be served at?

Cask ale is served at cellar temperature, which is cool rather than cold. Cask Marque, the accreditation scheme for cask beer quality in pubs, describes 11 to 13°C as the industry standard, and its drinker survey found that "97% of drinkers were happy with the industry standard of 11-13°C ie cellar temperature", while "when the temperature exceeded 14°C the satisfaction levels dropped to 52%." Adnams gives publicans the same 11 to 13°C cellar range.

That standard is not settled taste, though. The same Cask Marque survey found that "More than 56% who say that cask is there favourite beer say they would prefer it cooler than 11°C", and the page notes one brewer's new cask brand served at 5°C, as part of a wider argument that cooler cask could win over drinkers used to colder serves of craft beer and lager.

Keg beer is generally served colder than cask, chilled on its way from the cellar to the font. The Lincoln CAMRA piece notes that craft keg brewers say their beers "need to be served cold". That is a preference, not a verdict: in our view cold mutes aroma and sharpens refreshment, and which you want depends on the beer and the weather.

The old line that British ale is "served warm" is a misunderstanding: a cask pint at 11 to 13°C is cool to the hand, and only warm beside lager from a chilled font.

Why does the sparkler matter so much in the North?

On a hand pump, the end of the spout often carries a sparkler: a small nozzle that forces the beer through tiny holes. CAMRA's guide to the north-south divide in cask service says sparklers create "a tight creamy head on a pint of cask ale", and that "In most pubs in the North and Midlands, cask ale is served through a sparkler", whereas "Commonly in the South (particularly the South East) cask ale is dispensed without a sparkler".

County Durham sits on the northern side of that divide, so a visitor ordering cask there can expect a pint with a dense, tight head more often than not. If you prefer a looser head, it is reasonable to ask politely whether the sparkler can come off. Our guide to British pub etiquette covers how to make requests like that at a busy bar.

The flavour argument runs both ways. As the beer engine entry summarises it, "There is an argument that the sparkler can reduce the flavour and aroma", especially of hops, while "The counter argument is that the sparkler takes away harshness".

Why does cask ale go off faster?

Once a cask is in service, every pull of the pump lets air in to replace the beer, and air slowly oxidises it. Adnams tells publicans to make sure they can sell a cask within three days of first serving, and St Austell Brewery's trade quality team, quoted in the Morning Advertiser, says a cask "should always be removed after 72 hours – the three-day window is critical to cask quality." Not every brewery draws the line in the same place: Great Newsome says cask beer should ideally be drunk "within 5 – 7 days of tapping", and that "Darker and/or higher ABV beers will generally keep for a further 2 – 3 days."

Keg beer does not have this problem in the same way, because the sealed, gas-driven system keeps air away from the beer. That is the honest commercial case for keg: it is more forgiving of a quiet Tuesday.

For the drinker, a cask range that turns over quickly is a good sign; if the beer smells of vinegar or wet cardboard, or pours flat and dull, it is fair to say so politely and ask for something else.

Which one should you order?

Order the one that suits the beer, the moment and the pub; it is not a test of character. In our judgement, cask tends to reward traditional British styles: bitters, best bitters, milds, porters and many golden ales, where malt, gentle hop bitterness and a soft texture are the point. Keg tends to suit beers built around bright carbonation or punchy aroma served cold, such as lagers, many pale ales and IPAs, and it is the steadier choice in a pub that sells little cask.

If you are unsure, ask what is pouring well today. In a pub that keeps its cask properly, the person behind the bar will know, and it is reasonable to ask for a small taste before you commit. A cask bitter also sits comfortably beside the dishes in our list of British pub food classics, and our guide to things to do in County Durham can shape a day around the dales.

Cask ale and keg beer side by side

Sources

• CAMRA updates its definition of real ale (London Drinker, CAMRA)
• When is keg not really keg? (CAMRA Greater Manchester)
• Craft keg beer: what's that all about? (CAMRA Lincoln)
• Why is there a north-south divide on the way cask ale is served? (CAMRA Learn & Discover)
• Cask should be cooler (Cask Marque)
• Keeping tip-top cask beer (Adnams)
• Top cellar tips to ensure quality cask (Morning Advertiser)
• Cask beer: your questions answered (Great Newsome Brewery)
• Real ale (Wikipedia)
• Beer engine (Wikipedia)