In the 1950s, Scotland and Ireland’s whisky industry began acknowledging ex-bourbon barrels as desirable maturation containers. Three decades later, ex-bourbon barrels dominated both countries’ first-fill casks, adding staves to re-cooper into larger hogsheads.
Even as North America’s whiskey industry prospered from the 1870s, commanding more than 75 per cent of global production, Britain did not import American whiskey in casks. The limited export trade in bourbon was shipped to Europe for foreign bonding to avoid onerous federal excise taxes, and was re-exported years later as premium-aged whiskey at a lower customs rate. More than two thirds of exports were warehoused in Germany between the 1880s and 1890s until extended US ageing laws and rising European tariffs made this trade unwarranted and unprofitable. Then came America’s distilling ban in 1917, because of First World War rationing, followed by Prohibition from 1920, halting whiskey and barrel production until 1934. The Great Depression, rebuilding America’s aged stocks with fewer distilleries, was followed by the Second World War. All these setbacks prevented bulk bourbon exports, which meant Britain had no exposure to ex-bourbon barrels until after the conflict had ended.
During the first half of the 20th century, North American co-operatives supplied oak staves and new casks to British distilleries, as no trade existed in second-use barrels. In 1930, Canada and the US sent the equivalent of more than 350,000 new casks to British distilleries and breweries.
After July 1938, US Federal law required American straight whiskey to be stored once in charred new oak containers. Only bottles were permitted to leave the distillery to be sold, leading to a surfeit of stockpiled used barrels in the 1940s. On VE Day, 8 May 1945, Maslow Cooperage in Brooklyn, New York, began reconditioning ex-bourbon barrels for evaluation in British distilleries. It was a good move. By the late 1940s, Maslow bought the Victory Cooperage in Louisville, Kentucky, and the Peoria Cooperage in Ohio, to serve Scotland’s growing export demand for used bourbon barrels.
Since the late 17th century, Spanish sherry bodegas have prized American white oak for making wine, with the British whisky industry favouring ex-sherry casks for maturing whisky. When sherry casks proved too costly or hard to source, distilleries were forced to fill new, steam-purged, or chemically treated American oak casks. After the First World War, sherry butts became increasingly scarce. Similarly, the supply of the less desirable port and other fortified wine casks was also in decline. These cask shortages were alleviated by distilleries importing new oak from North America, supplemented by Memel, Polish, and even Persian oak during the Second World War. Distilleries treated the new wood to exhaust it of robust oak flavours, using it as the first fill for malt and grain spirits before finishing in fresh ex-sherry casks for a year or more.
The ex-bourbon barrel proved a production, economic, and flavour saviour for the Scotch and Irish whisky industries. In 1960, 1.5 million dumped ex-bourbon barrels were shipped to Europe; more than 800,000 were sent to Scotland. In 1965 volumes had grown to 2.5 million; by the 1970s, bourbon was the leading first-fill cask, and by 2000, it made up more than 95 per cent of the total used. Blended Scotch accounted for 99 per cent of Scotch consumption in the 20th century. Fortuitously, blended Scotch employed the vatting of dozens of malt and grain whiskies that masked flavour differences between casks.
For the malt drinker, ex-bourbon maturation served a new consumer, with a softer mouthfeel and sweeter taste, with nuanced flavours of vanilla, caramel, and coconut. In the 1980s the Scotch trade described ex-bourbon whisky as “buttery and pale”, plain American oak “Chardonnay malt”, and Spanish ex-sherry oak (American and European) as “fruity and dark”. By the 21st century, the ex-sherry butts, once defined as Genuine Scotch, were replaced by ex-bourbon barrels as new-generation Scotch whisky.