All beer starts out the same way, more or less. A sweet porridge-like substance is concocted by dissolving malted barley (and sometimes other) grains with hot water - or liquor as it is known in the trade - and this is then boiled together with hops. The result then has yeast added to it, which reacts with the sugars extracted from the grain, and the liquid ferments to produce alcohol.

It is what happens next that counts. Once the beer has finished its main period of fermentation, it is poured (or ‘racked’) into casks. These will usually be either 18 gallon ‘kilderkins’ or 9 gallon ‘firkins’. The beer is not filtered or pasteurised and so it still contains some of the yeast. This will bring about a secondary fermentation in the cask, which produces the natural gas giving the beer its ‘condition’. Most real ale is ‘cask-conditioned’. Real ale in a bottle (RAiB) describes bottled beers containing live yeast.

Keg beers are effectively ‘killed off’ at the brewery and the gas is added artificially, but at a higher pressure than naturally, giving keg beers their ‘fizz’.

To see a very good explanation of what the ‘Perfect Pint’ should be like see Steve Williams’ short video on ChannelBee.com and if you like that then read his blog at beerjustice.blogspot.com.