Is there a spirit as wonderfully diverse as Whisky? With every expression offering up a different aroma, flavour, texture and even colour, it would be a hard argument to counter. Variety is the spice of life – and in regards to our golden subject, we have the relationship between wood and Whisky to thank.

What gives Whisky its flavour? There are a number of factors and processes in the Whisky-making life-cycle that influence the tasting notes of the final expression: the process of chill-filtration, distillation, raw ingredients, where Casks are stored, the length of maturation…But, perhaps none quite as significant as the wood chosen to mature the Whisky.

How much the choice of cask influences the end result is hotly debated within the Whisky industry – depending on the distiller or blender questioned, it’s not unusual for wood to be credited for 60-80% of the final flavour!

Wood and Whisky - What are Casks and How do They Work? 

The making of Scotch Whisky is heavily protected and regulated. As a result, distillers and blenders must follow a strict set of guidelines in order to ensure their Whisky is legal – one such rule is the requirement to mature their products only in oak casks. This means that spirit matured in any other type of wood – e.g. mahogany, could not be labelled as Scotch Whisky.

On the face of it, this may appear to be quite restrictive, however, when considering the abundance of species of oak in existence, terroir, durability, leak prevention and its ability to transpose flavour, the potential to create a truly unique expression is unlimited.

Scotch Whisky is generally matured in either American or European oak. In order to create a certain style or flavour, distillers and blenders will buy casks second-hand that have previously been used to mature other types of alcohol – such as wine or sherry. Over recent years, a growing trend has seen Whisky makers begin to experiment virgin oak (untouched, brand new) casks due to their ability to impart flavour more quickly than those that are “well-lived” in. Unlike with American Bourbon, where casks must only be used once in a brand new state, Scotch Whisky distillers may re-use a cask two or three times until it is deemed to no longer impart the required amount of flavour. At this stage, the casks may be sold on or discarded altogether.

Same distillery, same spirit, same maturation period, same wood but different Whisky? Each individual cask offers up its own specific properties – to establish consistency, distilleries will typically marry together many casks to create a steady product line. However, Whisky labelled as having been charged from a “Single Cask” will have been extracted from just that - only one cask – and as such will offer up tasting notes different to any other Whisky in existence.

The number of bottles that a Single Cask will yield will be dependent on the type and size of Cask – but regardless of size, because the Whisky has been drawn from a finite source, the number of bottles will always be relatively small, making Single Cask Whisky significantly more desired and covetable. It’s essentially Whisky in its purest form.

That’s not to say that marrying together Single Casks cannot yield superior results. As seen with the Remarkable Regional Malts – our Blended Malt range – master blenders can treat Single Casks as individual musical instruments, of which are then married together create a harmonious orchestra of flavour!

Further flavour can be derived by “finishing” Whisky in a cask of a different origin – a process sometimes referred to as double or secondary maturation. This is the process of maturing Whisky within one cask, and at a later stage of maturation, pouring the contents into a different type of cask for a period of time. The spirit from within a cask will draw out the natural oils of the cask wood, so repeating this process twice can create further flavour. Not all finishes are made equal though – distillers and blenders have to predict a complementary combination.

Wood and Whisky - Types of Casks and Their Flavour

Casks come in all shapes, sizes and finishes. The availability of a certain type of cask – say, Bourbon can impact the final price of a Whisky. Put simply, some casks can be harder to come by than others due to economic and environmental conditions.

Whisky bottles will usually be labelled with the type of cask it was matured in. Although no two casks are ever the same, they do usually yield similar flavours.

• Port Pipe – Holding around 600 litres of spirit, this type of cask is one of the largest used to mature Whisky. As the name would suggest, in a previous life this type of cask would have been used to hold and develop port wine. As one would expect with a port influence, Whisky finished in this style of Cask will typically be fruity and offer up tasting notes of summer or berry fruits. Depending on the type of port used, the Whisky within this cask may eventually develop to a darker, reddish colour.   
• Butt – Smaller than the aforementioned Port Pipe, a Butt will usually hold up to 500 litres of spirit. Sherry Butts are used most commonly to finish Whisky. Similar to the Port Pipe, a Sherry Butt will create an intensely fruity flavour – with sultanas and dark fruits featuring frequently as tasting notes. As with the Port Pipe, a Whisky matured in a Sherry Butt will typically take on a red appearance.
• Puncheon – A puncheon (typically used first to mature Sherry or Rum) is the same size as a Butt. Whisky matured within a puncheon will give way to a very sweet, fruity characteristics. As seen recently with our sensational sell-out Old Particular Glen Moray 10 Years Old, Whisky matured in this style of Cask may take on a dark chocolate appearance, hinting at the incredibly rich palate within. 
• Barrique – Significantly smaller than the previous casks, a Barrique will hold up to 300 litres of spirit and is typically used beforehand to mature either wine or port. The tasting notes for a Whisky matured in this style of cask is dependent on the wine used before. The same applies to the appearance of the final expression too. 
• Hogshead – Holding 50-75 litres less than a Barrique, the humble Hogshead is a favourite choice of distillers and blenders. Hogsheads will usually have spent their previous years maturing Bourbon, meaning the later matured Whisky will develop sugary-sweet tasting notes – often with strong influences of vanilla. Visually, the resulting Whisky will usually be golden in colour.

Given that a particular Whisky may be destined to mature for many, many years, an investment into the right types of casks is a very weighty decision – one, in fact, that can only ever be made by an exceptionally experienced Whisky master.