be "tapped" by punching the pre-cut centre of the (traditionally cork) bung (at the lower edge of the barrel end) into the barrel by hitting the tapered brass "tap" with a mallet. One could then attach the pipe connector onto the tap, so that the cellarman could turn the tap on when ready. In a similar manner, one would punch through the centre of a bung on the upper side of the barrel's belly with a hardwood spile (tapered peg). The hardwood spile prevents air access. Once the barrel is in use, the spile is replaced with a "soft" spile, traditionally made from softwood, but nowadays from bonded-together (woody) fibres. The soft spile prevents a vacuum forming at the upper surface of the beer: it allows sufficient air in for the beer engine to work, but keeps dust, flies and other mischief-makers out. Keg ale Keg beer is a term for beer which is served from a keg, under external carbon dioxide pressure. Keg beer is often filtered or pasteurized, both of which are processes that can render the yeast inactive, increasing the shelf life of the product. However, some believe this is at the expense of flavour. In the early 20th century, draught beer started to be served from pressurised containers. Artificial carbonation was introduced in the United Kingdom in 1936, with Watney's experimental pasteurised beer Red Barrel. By the early 1970s the term "draught beer" almost exclusively referred to beer served under pressure as opposed to the traditional cask or barrel beer. The Campaign for Real Ale was founded in 1971 to protect traditional – unpressurised – beer and brewing methods. Keg beer was replacing traditional cask ale in all parts of the UK, primarily because it requires less care to handle. The campaign group devised the term real ale to differentiate between beer served from the cask and beer served under pressure. Nitrokeg Nitrokeg dispense is a variation on keg dispense, using a gas mixture emphasising nitrogen instead of carbon dioxide (CO2). It is associated with stouts and Irish "red" ales. Nitrogen is used under high pressure when dispensing dry stouts (such as Guinness) and other creamy beers because it displaces CO2 to (artificially) form a rich tight head and a less carbonated taste. This makes the beer feel smooth on the palate and gives a foamy appearance. Premixed bottled gas for creamy beers is usually 75