During the 1780s, malt and grain spirits in Ireland and Scotland underwent a major flavour transformation. Consumers desired whisky that was well stored in a cask, as time in wood made whisky mellower, richer, and more complex in flavour. The superlative container was the ex-sherry cask.
Earlier, uisge-beatha and proto-whisky had little or no wood maturation, except for brief exposure in transport from still to consumption. It was either consumed raw or, preferably, compounded with herbs, spices, and sweeteners, often drunk as toddies, the cocktail precursor. Cheaper than buying new casks, distilleries began to refill unclaimed emptied ex-wine, brandy, and rum casks to store whisky, where the residual alcoholic flavours and second-use wood suited the flavour development of barley-based malt whisky. The sherry butts from southern Spain imparted highly desirable flavours, acting as a vinous flavour bridge between fortified sherry and French brandy, the most consumed wine and spirit in the British Isles. From the late 17th century, Jerez winemakers preferred butts made from American white oak, less tannic than European oak. The rise of whisky in Britain was the rise of sherried whisky. For the next 200 years, ‘genuine Scotch’ and Irish whisky was fully or partially matured in ex-sherry casks.
Ex-sherry casks underwent marked flavour progressions, from virtually no oaken flavour in the first half of the 19th century to oak-dominant expressions in the 21st century. The fickleness of generational drinking fashions saw sherry wine demand soar and then decline, impacting the trade in casks and forcing the whisky industry to adapt and innovate, resulting in responses to three discernible phases.
Sherry boom phase: The first flavour progression gained momentum from 1800 to the mid-1870s when British sherry consumption grew sevenfold, and Scotch whisky production increased tenfold. Britain imported most of Spain’s sherry production, exported in 500-litre casks, botas de embarque or de exportación. Agents paid for the return of empty butts to the bodegas as sherry vintners wanted to reuse old casks to maximise wine oxidation and minimise extractive oak compounds tainting sherry wines. With the whisky industry’s growing demand for sherry’s decades-old soaked butts, distilleries and dealers were willing to pay more and diverted empty butts for whisky storage. Many were repurposed into smaller 250-litre hogsheads for easier dunnage stacking and more efficacious maturation.
Sherry shortage phase: Cask shortages became chronic after 1873 when sherry consumption declined while whisky production grew. In phase two, pre-treated new casks were introduced for first fill, followed by finishing in fresh ex-sherry casks or recycled distillery butts. Alternative flavouring methods also attempted to imitate the flavours of sherry, such as the widely popular Thompson’s patented prune juice extract from the 1860s or substituting cheap Hamburg sherry (European wines fortified with potato spirit). In 1890, William Lowrie patented a pneumatic injection process, later called paxarette, suffusing heated sherry into the staves of new oak containers and reviving older spent sherry casks for another fill for repeated usage. Scotch production doubled from 16,869,835 gallons in 1874 to 35,798,465 in 1899, as sherry imports fell by a third from 68,467 butts to 45,349 butts, exacerbating the sherry cask shortage that continued throughout the 20th century as sherry consumption declined.
Sherry bans phase: Preventing fraud and protecting the sherry’s reputation, in 1986 the Spanish government mandated that all sherry be locally bottled, ending the export of bulk sherry in cask. Two years later, the British government banned the paxarette treatment of casks in Scotland. To remediate the loss of export casks and paxarette, whisky distilleries sourced newly coopered faux-sherry casks from bodegas, briefly soaked with sherry, before filling with new make in Scotland to create the modern iterations of oaken ‘sherry bombs’. The saga of sherried whisky is the exposition of adaptation.
