How Wood Imparts The Flavour of Glenfiddich Whisky

27 February 2015

Here at Glenfiddich, the quality and lineage of the casks we use is key to ending up with the highest quality whisky possible – as much as 60% of our whisky’s flavour comes from the cask it is matured in.

Glenfiddich casks are crafted by the most skilled of men: the cooper. A job which takes guile, physical strength and years of training to master; the vessels they make must eventually cradle precious single malt whisky, often for decades, and work in partnership with the spirit to deliver something unique, rare and of the upmost quality.

We recently chatted to Ian McDonald, Head Cooper at the Glenfiddich Distillery, and an integral member of the team for over 45 years, about the importance of the casks we use and, more specifically, just how the wood they are made from impacts the award-winning taste of our whisky.  

For those readers who are not so familiar with coopering and why it is so important to the process of excellent whisky making, when you describe what you do to your family and friends, what would you say?

By law, whisky must be matured in oak casks which are made and maintained by qualified coopers. The barrels we use are ex-bourbon barrels shipped in from North America. Each barrel is inspected on arrival and the good ones go direct into the filing store for filling and the rejects, with cracked staves and damaged ends, come to the cooperage for repair.

How long have you been a part of the Glenfiddich family for?

I joined William Grant & Sons in April 1969 (almost 46 years ago) having left school at the age of 15. Although I started in the casks shed, preparing the casks for filling, it was the Cooperage that I was always destined for. Once the company gained permission to start an apprentice programme, I was transferred in and started my five year apprenticeship under the supervision of my journeyman, Don Ramsay.  

How has the cooper's art changed over the years?

Repairing casks has not changed much although a lot of the heavy hammering has been removed with the introduction of hydraulic machinery - for example, we now have hoop pullers for removing hoops, rivet banks for riveting hoops and hoop drivers for hardening the casks. Cosmetically the barrels are not ‘dressed up’ like they used to be but today more importance is given to the actual quality of the wood for maturation; in years gone by, a cask was just a container for the spirit but today the importance of the wood is fully recognised. 

Rejuvenation of casks actually started in the mid 1980s and was done by removing the old, exhausted surface inside the casks to uncover fresh wood. The inside of the cask would then be toasted with a gas burning lance at a set temperature to give the cask another lease of life, preventing it from being discarded indefinitely. 

Just how important is an on-site Cooperage in contributing to the success of our award-winning whisky?

Wood quality is absolutely paramount. To produce award-winning whisky, it’s crucial we make sure our wood is of the best quality and each one needs to be able to stand the length of time expected for the whisky to mature, be it for 12 or even 50 years.  

How important is wood in effecting the flavour of our whisky?

Wood is crucial not only in affecting the flavours and colour in maturation but also in finishing the product. For example, American Oak casks will give the whisky a vanilla, honey and citrus fruit flavor, whilst European oak imparts richer spicier flavours and hints of dried fruit. Consideration must also be given to those casks that have been filled once, twice or even three times, as this will inevitably affect flavour too. 

Where do the casks that we use originate from?

The barrels we use originate from America and we buy them from various sources including the Kelvin Cooperage, Barrels Unlimited and Jim Beam. Our European casks come from Jerez, Spain.

Describe to us the typical lifecycle of a cask...

A typical cask could have a life span of well over thirty years depending on the number of times it has been filled. Usually it will have been filled between three to four times but each refilling requires the cask to be emptied (disgorged) and the character/colour of the whisky assessed to determine whether it warrants repairing. There are some casks in our warehouse that are over 50 years old. However, the average age is probably closer to between 30 and 40 years. 

How many casks go through the Cooperage in a day?

On average, about 200 casks go through the Cooperage in a day.

What's it like working for a family run business?

Working for a family run business has definitely given me a greater sense of security. Glenfiddich have long-term plans and the family is always investing to improve the business as much as possible. From starting out at the age of 15, I feel I have grown up as part of the wider Distillery family. 

There’s no prouder feeling than when you’re wandering through duty free shops at the airport or supermarket aisles and you see the award winning products you have helped to produce lining the shelves.

What is your favourite Glenfiddich expression?

Genfiddich 15 Year Old is my favourite expression as I love its full, smooth-bodied sherry influence and the rich sweetness in flavour given to it by our Solera process.  

In terms of the flavour it imparts, which type of cask is your favourite?

The sherry butt - I like the rich sweet and spicy flavours it imparts on the whisky.

For a rare peek into our onsite Cooperage just head to our YouTube channel. Alternatively, you can see what happened when we spoke to Glenfiddich Cooper, Sean Caird, on-set at the photo shoot for our 18 Year Old expression’s redesigned packaging.