As distillery tour guides in both Kentucky and Scotland love to tell visitors, bourbon barrels can be used only once for bourbon, part of the regulations governing the spirit. After their single use in the US, the barrels are usually sold on to whisky makers in Scotland, Ireland, Canada, and elsewhere. This arrangement works out splendidly for both parties, as bourbon distillers can recoup some of their investment in the wood and other whisky makers get a steady, affordable supply of casks with plenty of life left in them.
Tucked into a typical Scottish warehouse, first-fill ex-bourbon barrels reliably yield flavors of vanilla, caramel, and honey – lovely on their own, and also a sturdy canvas for layering finishes such as sherry, port, and rum. About 90 per cent of Scotch whisky is aged in ex-bourbon barrels. They are undeniably critical to the existence of every brand of Scotch on the shelf. And that could end up being a big problem.
In the last decade, the American whiskey industry has begun adopting a dumping technique that changes the way the barrel behaves when it goes on to its next life. After emptying barrels of mature whiskey, distillers are filling a few gallons of water into the wood, “rinsing” it of any excess spirit (sometimes using pressure or jets), and using that liquid in the proofing process. It’s a cost saving for them – they get more alcohol per barrel – but potentially disastrous for Scotch, because water-rinsed barrels mature single malt very differently from their standard counterparts.
John Glaser, founder and whisky maker at Compass Box
, noticed the phenomenon in 2013. “We weren’t getting the kind of first-fill bourbon barrel effect we were expecting – it was not nearly as noticeable in terms of wood extract,” he says, comparing it to what might result from maturation in a refill hogshead.
At about the same time, master blender Dhavall Gandhi – formerly of Macallan and The Lakes Distillery
– experienced the same thing. He realised that some ex-bourbon barrels he received from brokers weren’t yielding the expected profile in ageing single malt – what he calls “boiled sweet character”. So, he ran an experiment, filling two sets of casks: one regular first-fill ex-bourbon, the other water-rinsed first-fill ex-bourbon.
For a year and a half, and in some cases even longer, Gandhi followed the maturation. “There was a difference in sweetness, there was a difference in certain vanillin pick-up, there was a difference in colour pick-up,” he says.
The practice of water rinsing, also called water soaking, is shrouded in mystery. When selling casks to brokers, many bourbon distilleries don’t share whether they are rinsed, so UK whisky makers are often operating blind, though Gandhi doesn’t think this is due to bad intent on the part of bourbon distillers. “They might not realise that by doing this, what would be the impact downstream,” he says.
Bourbon distillers are, rightly, focused on their own needs. Conor O’Driscoll, master distiller at Heaven Hill
, which does not rinse its barrels, says the practice typically yields an additional two proof gallons of whiskey per barrel. “It’s an efficiency,” he explains. “It’s whiskey that you’re not giving away.” And although there’s a cost to setting up a facility for water rinsing, it may be outweighed by all the recovered whiskey, especially if demand has gone up between the time the barrels were filled and when they are dumped.
Big bourbon producer Heaven Hill does not rinse its used bourbon barrels
Regardless of intent, the growing wave of water-rinsed bourbon barrels is having an impact on Scotch whisky, especially for smaller producers. Whereas a large-scale blender might be able to more easily integrate water-rinsed casks into its maturation scheme, which includes a variety of other cask types, a smaller company, working with fewer barrels to a batch, will have less of a buffer.
Gandhi compares the effect to a disruptive student. “When you have a small classroom, and you have 10 students in a class, if one is a bit noisy or one is a bit quiet, you know right away who is noisy, who is quiet,” he says. “But if there are 100 students in a room, the one or two blend in.” Gandhi would like to see more transparency about which barrels have been rinsed, which would enable him to more easily compensate for the different profile. “If I don’t know what I’m playing with, how am I going to plan all my projects for the future?” he says.
Large distillers may also more easily afford traditional ex-bourbon barrels, which now command a premium compared to water-rinsed casks. But as water rinsing becomes more widespread in bourbon country – whose stocks are in a crunch, as demand for American whiskey continues to grow – even they won’t be immune. Oliver Chilton, head blender at Elixir Distillers, notes that the practice is in use at bourbon distilleries owned by multinationals, whose barrels presumably go on to their Scottish counterparts – and that’s apparently not a concern, at least not yet.
But it’s only a matter of time before the effect becomes evident in the bottle. “This is changing the character of what we have called a first-fill bourbon barrel for a long time, and it therefore is going to change the character of mature whisky in X number of years when you come to use it,” Glaser says.
This is not the first time that Scotch whisky has faced down the potential impact of changing cask supplies. After a regulatory change in 1981 which required that all sherry be bottled in Spain, the supply of shipping casks, which had been reused by whisky makers in Scotland and elsewhere, dried up – and the industry adjusted. Nowadays, the majority of sherry casks used for Scotch whisky maturation are purpose-built and filled to spec for distilleries, ensuring a steady, and more consistent, supply.
A similar solution could be on the cards if water-rinsed bourbon casks pose sufficient threat to the big distilleries. Compass Box is already adapting: in 2013, Glaser developed a custom virgin oak cask programme to make up for some of the wood flavours he needed. Compass Box’s virgin oak casks are made in the US and filled in Scotland with grain spirit for a year, then used for long-term maturation of both malt and grain whisky.
But the company has also leaned into the spirit-forward flavour profile created by water-rinsed casks, launching a permanent expression, Orchard House
, to showcase it. The blend of mainly Linkwood and Clynelish, with a few other components in smaller amounts, debuted in autumn 2021 and marks a departure from other core whiskies in the blender’s line-up, though Glaser sees a potential rise in drinkers seeking such profiles. “I want to taste the individuality of the core components,” he says, “instead of obscuring it with a lot of oak or wine character. I like oak and I like wine character, but keep it in balance.”
Ultimately, water rinsing isn’t going away. Chilton speculates that those bourbon distillers who don’t currently do it simply haven’t invested in the right equipment and space yet. While he once saw the phenomenon as problematic, he is starting to change his view.
“I think a lot of Scotch whisky is quite restricted,” he says. “I’m not talking about the rules. It’s almost like a mentality. ‘This is the way we’ve done it. This is the way it’s done.’” And that attitude, he explains, can be limiting. “Whereas today, the more you experience global whisky, you look at trends, the way people are behaving... When you’ve got a problem, it’s not a problem. It’s just an opportunity to create something slightly different.”