By the Middle Ages, the wooden cask had consolidated its position as Europe's primary storage and shipping container and was well established in European feudal culture. The organisation of coopers, known as The Worshipful Company of Coopers, was awarded its royal charter of incorporation in 1501. The oldest surnames in the English language are derived from the main professions in medieval village life: the stoneworker took the surname Mason, the blacksmith was Smith and the barrel-maker was known as Cooper, which comes from the Latin, 'cupa', meaning cask. Today there are approximately 151,000 UK nationals with the surname 'Cooper', making it the country's 35th most common surname.
Coopering organised itself into four distinct disciplines: the dry or slack cooper made casks for shipping dry goods such as grains, nails and textiles. The dry-tight cooper made watertight casks for transporting moisture-sensitive substances, such as flour and gunpowder. The white cooper made straight-staved casks like pitchers and vats, and the wet or tight cooper made casks for the transportation and, when required, maturation of liquids.
Over time, brewers and distillers learnt the different properties that various woods could impart to their beverages. Oak became the wood of choice because it was plentiful in Europe and North America and because it also offered a uniquely appealing combination of flavours: the porous nature of an oak barrel allows evaporation and oxygenation to occur in wine but typically not at levels that would cause oxidation or spoilage. Its chemical composition also offered a uniquely appealing combination of flavours: Vanillin (the aroma of vanilla), Eugenol and Isoeugenol (spice and clove notes), Furfural and 5-Methylfurfural (caramel and sweet aromas), Guaiacol and 4-Methulguaiacol (charred and smoky aromas).
It was also discovered that toasting or burning the inside of casks to varying degrees could alter and enhance the flavour of a maturing beverage. The charring caramelises the sugars in the oak resins, sweetening the liquids stored inside. It has been suggested, probably apocryphally, that the insides of casks used for storing pungent foods such as pickles or fish were burnt and scraped in order to sterilise them and rid them of unpleasant odours, and that this led to the accidental discovery of charring.
Despite recent drops in world wine and Scotch Whisky consumption, wooden casks seem likely to be around for the foreseeable future, not least of all because our increasingly sophisticated palates are demanding an ever greater range of artisan, cask-aged products. As with every other facet of modern manufacturing, technology is having an impact, too, with near-infrared technology now available to assess the chemical composition and measure the precise quantity of tannins in any given piece of oak.
Today's cooper makes casks primarily for wine or whisky (or whiskey). The whisky industry has kept coopering alive in Scotland where a few distilleries still employ coopers in-house and traditional cooperages like the family owned Speyside Cooperage, whom Bruichladdich uses, are still able to flourish; south of the border the art has been so neglected since the introduction of metal beer-barrels that there is perhaps only one remaining master cooper. In spite of the increased use of wood chips to impart flavour to wine, the cooper's art is still esteemed in parts of mainland Europe. Some oak casks of French origin are particularly highly prized with examples selling for as much as £3,000.