Burton Union fermenters

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Burton Unions were developed in Burton-on-Trent in the UK in the 19th century to cleanse the new pale ales of yeast.

The fermentation takes place in giant oak casks linked together by pipes and troughs. The fermenting wort and yeast, as it heats, rises up swan necked tubes up into the troughs. The wort runs back into the cask but the yeast is trapped.

The last of the Burton Unions in the UK is used at the Marstons brewery and is housed in a series of rooms that are known as the "Cathedral of Brewing". In the United States, Firestone-Walker brewery uses a similar "Firestone Union" process originally fashioned from used wine barrels.[1]

Marston's is also the only remaining brewer to use Burton Union Sets; a system whereby fermentation barrels and troughs are linked together by a complex system of copper and brass pipework. The basic principle is one of preventing excessive beer and yeast loss through foaming, but the consequence is that the beer is both in contact with more wood and in contact with more beer (fermenting in a bigger volume). This results in a vastly more consistent flavour; and very little chance of a whole batch being ruined.

All other large-scale brewers have abandoned this method in favour of stainless steel vats, which while they assure (through volume) a consistent flavour, do not permit the use of traditional yeast varieties. They also make selective use of the unusual double dropping process which introduces complex flavors due to a period of accelerated yeast growth.