Cask ale? Keg beer? Lager on tap? What does it all mean? And how come you never hear of cask lager?

If you’ve seen the words keg and cask around but never stopped to think what they mean, now’s a good time to find out.

Keg

A keg is a small barrel, usually made from stainless steel.

The standard keg size in the United Kingdom is 11 gallons (50 litres, or 88 pints).

Kegs are used to store beer, and other alcoholic and non-alcoholic drinks. They’re often pressurised for keeping carbonated drinks fizzy (they’re basically massive cans of pop). Kegs have a single opening on one end, called the bung. It’s also got a mechanism with a self-closing valve that allows gas (usually carbon dioxide – the bubbles in fizzy stuff) to push the liquid out.

This isn’t the fizzy bubbles in the drinks themselves – they’re not powerful enough to push the beer out. Instead, a gas pump fitted in the drinking establishment will be connected via a hose, into the keg, which pushes the carbon dioxide in, and the drink out. (Different gases are sometimes used for smoother beers like stouts.) The system is cleverly set up to pump out near enough all the liquid in the keg, and alerting staff they need to change it.

You’ll be able to find smaller mini kegs of beer to purchase from supermarkets and drink shops all around the country, which are usually 5 litres (8 pints) in size. The bigger ones are used by pubs and clubs all around the world to pump beer into the draught taps at the bar. ‘On draught’ means straight from the keg, through the tap, and into your pint glass. They’re usually kept in temperature-controlled cellars, and passed through cooling pipes on the way, meaning the stuff you drink ends up being nice and cool.

Beers in kegs are usually pasteurised or filtered too, to make sure there aren’t any active ingredients in them, prolonging their shelf life and maintaining a consistent taste between batches.

Keg beer, then, isn’t a type of beer, but it’s a way of containing, transporting and dispensing the beer.

Cask

A cask is a large barrel, wooden or metal, which you’ll have seen stored lengthways in brewery cellars, sometimes with a spout pointing out of the end. It’s cylindrical, with a centre bulging out, bound by wooden or metal hoops. Casks are used to store beer, but also whiskey, wine, cognac, port, and other types of alcoholic beverages.

Cask ale, then, is also not a method of brewing, but one of containing and dispensing. It’s the original method; the way beers have been kept for centuries.

It’s often interchanged with the term ‘real ale’, which was a rather opinionated term coined by CAMRA for the more traditional type of cask beer.

Cask ale is a ‘live product’ – it contains active yeast. If a pub gets a cask of beer in, it’s not ready to serve straight away – the brewing continues after they get it. They need a bit of time and care to produce a good end product. Pubs that do it well are the ones that get reputations for serving great beer and often win awards.

Casks need racking (placing securely where they won’t be disturbed, affecting the flavour), tapping (using a mallet to whack a tap into the side) and venting (letting out the gas produced by the fermenting yeast, while keeping the beer in). Finings are then added – these are substances which draw yeast and sediments to the bottom of the cask (often made from animal products like gelatin or isinglass, which means many beers aren’t suitable for vegetarians or vegans). The cask is then left for around 48 hours for the process to complete.

The result is often a tasty, unique, complex and flavoursome beer that’s best enjoyed closer to cellar temperature (9-12 degrees C). Casks should last around 3 days before oxygen gets in and starts affecting the flavour negatively. Beer is flowed from the cask via a ‘beer engine’ system, using gas assisted pumps (the ones that bar staff pull) to get it into your pint glass.

Is cask or keg better?

Whether cask is ‘better’ than keg beer or not is just a matter of opinion and personal preference.

And as for cask lager – it does exist, some brave brewers have tried it, but it’s a bit niche. The lack of carbonation doesn’t play nicely with the expectations of a bubbly refreshing lager, and warmer serving temperatures don’t help, either. Technically it can work, it’s just not a very popular choice.