Should Whisky Warehouses Be Heated?

Can heating a warehouse speed up whisky maturation? And why is it taboo in Scotland?

We dive into the impact of temperature on whisky aging. From the rapid maturation of bourbon in Kentucky to Kavalan’s double-season method in Taiwan, they explore how heat and climate shape whisky. But in Scotland, heating a warehouse goes against tradition—though some say it might still be happening...

What do you think? Should whisky makers embrace heated maturation?

• Read the Full Transcript

  Bari Reid:
  So, like, one thing that we looked at in the past is, can you heat a warehouse, or how do you go about that.

  Gareth Roberts:
  Not in Scotland. The Scotch Whisky Association say it's against the spirit of making whiskey in Scotland, which means the law doesn't say anything about it, but we'd rather you didn't do it, lads. That's what it means.

  
  And then there has been some chat that suggests to me that there might be the odd heated warehouse in Scotland, but...

  BR:
  I've heard some of that chat as well. But I don't know.

  GR:
  I genuinely don't know if that's true or where it would be. But there's nothing saying that in Ireland, in England, in Wales, you can't heat your warehouse. So why would you want to do that? It's because when you've got a warm place in the States, you're making... in Bourbon, Kentucky or somewhere like that, or, India, it matures spirit really really quickly, and of course that's the big problem for whisky makers, it's length of maturation, trying to get your cash back but you can always tell in the product, you can taste a spirit that's been matured, abnormally, you know, it's been speeded up so, would you want to do it, maybe you do it, maybe you blend back.

  BR:
  But what's the, is it to raise, would you is it to, like, do you raise the base temperature, or would you have the fluctuations, because is it not the is it not the fluctuations in the temperature that...

  GR:
  Well you drive in, like I always do that, like you drive in the spirit into the wood, and back out, so it's breathing, it's actually the reaction with the oak, it's happening with the seasons, as it expands and contracts, it's transpiring through the cash, James Swan used to talk about someone did this test where they wrapped casks in cling film to see what would happen and nothing happened. It didn't mature because it couldn't breathe. It couldn't do that thing.

  
  I was at a distillery in the summer and they were saying that they're not in Scotland and they do heat to mature. He implied to me they do two seasons per year. They have a winter, a summer, a winter, a summer every year. They double mature it if you like. That whole realization came from Kavalan in Taiwan and from Indian whiskeys where you're getting three-year-olds.

  
  The rate of evaporation is 25% a year compared to Speyside. It's 2% a year. We're maturing very slowly, losing a little bit to the angels. 25% a year, three years, it's gone. Four or five years, there's nothing left. In fact, I think it's a rum that we were given by an Indian client, and it was called the 1%, and a warehouse had fallen down, and it had some rum in it. And they went and they found just a few casks at the back of the warehouse, and it had 1% liquid left in it, virtually dry. And that was this rum. And everything else had gone. It had all been lost because they'd left it just a year too long. So that, the effect of temperature on casks, is really interesting and exciting and makes a massive difference to the product at the end of the day.