Cask conditioned

Cask ale or cask-conditioned beer is unfiltered and unpasteurised beer which is conditioned (including secondary fermentation) and served from a cask without additional nitrogen or carbon dioxide pressure. Cask ale is also sometimes referred to as real ale in the United Kingdom, a term coined by the Campaign for Real Ale, often now extended to cover bottle-conditioned beer as well.

Cask means container. The Histories of Herodotus, written in 424 BC, refers to "casks of palm-wood filled with wine" being moved by boat to Babylon, though clay vessels would also have been used. Stout wooden barrels held together with an iron hoop were developed by the north European Celts during the Iron Age for storing goods. Over the centuries other methods have been developed for preserving and storing beer but this method is still used, particularly in Britain.

Bottled beers were commonplace by the 17th century for the well off who wished to drink outside of public inns, or who wanted to take a beer with them when fishing. There is a famous story of Alexander Nowell, the Dean of St Paul's, who, in 1568, left his bottled beer by the river bank, and upon returning a few days later discovered the bottle opened with a bang and that the contents were very tasty. But while the middle and upper classes could indulge themselves with such expensive luxuries, the ordinary folk continued to drink their beer served direct from the cask. India Pale Ale (IPA), the famous ale that was shipped to India, was delivered in casks, and only transferred to the bottle for the civilian middle classes; the troops drank their beer the same way they drank it back home, from flagons filled direct from the cask. But as beer developed and became paler and lower in alcohol, so it became more difficult to keep it fresh tasting in the cask, especially in countries with warmer climates. By the late 19th century commercial refrigeration and Louis Pasteur's flash heating method of sterilisation prolonged the life of beer. In Britain's cooler climate these methods did not catch on at this time.

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