Maturation

Thursday May 16, 2024

Every ‘new make’ spirit is clear when it runs off the still. It surprises some people that any colour that a finished spirit has, is achieved ‘after the fact’.

Whiskey is a classic example of this. When virgin whiskey is put into casks, it takes on colour fairly quickly. However, colour is only a part of the story. You need time to impart the vanilla, caramel, tobacco and leathery notes that are so prevalent in whiskey. There is also the ‘Angel’s Share’ to consider. Evaporation is an integral part of the maturation process but it can be alarming to crack open a barrel, only to find that the angels have taken half the barrels content, or more! However, air exchange through the pores of the oak is critical in giving us those darker tobacco and leather flavour notes.

The inside of whiskey barrels have to be burnt. Charred, may be a better description but the oak has to be subjected to a heat source to caramelise the wood sugars that the spirit can dissolve. Seasonal temperature fluctuations, forces the spirit in and out of the charred wood and it’s this process that gives us the colour and the caramel and vanilla notes. Of course, geographical location plays a huge part in this process. In the blistering heat and bone chilling cold of the Kentucky seasons, a cask can mature in four years, however, in the more temperate climate of Scotland, a barrel can age for three decades before it reaches its zenith.

Glue or nails should never be used in the construction of the casks. Nails can oxidise and impart flavours and the chemicals in glue can leach out into the spirit. When you consider the whiskey can sit in these casks for upwards of thirty years, we should take every precaution possible against tainting the spirit. The only thing that holds a barrel together are it’s steel hoops. Although applied with a great deal of force, the casks are made ‘water tight’ simply by the coopers’ skill to make the joints between the staves. However, when a cask is first filled, it can leak. As a precaution, the barrel should always be filled with water to allow the wood to swell and allow the joints to seal. It’s better to lose water than the precious new make whiskey!

Almost all casks that are built to mature spirit, are made from oak. The two main species are French oak (Quercus Robur) and American white oak (Quercus Alba). There are sub species within all oak regionalisations but mostly these are the two main species we should explore.

The European oaks have nine times the amount of tannins than American oak and as a result imparts more spicy notes to the finished spirit. Being less dense than its American counterpart, it generally results in a lighter colour with more harshness.

American white oak, accounts for the majority of all casks that age spirit. Producing vanilla, caramel, baking spices, coconut, leather and tobacco notes, they are responsible for so much of the flavours found within whiskey.

Japanese oak has become a hot topic due to the increased prestige of Japanese whisky over the last two decades. Quercus Mongolia imparts Oriental incense, sandalwood, spice and coconut notes, but this oak has an unruly grain with an abundance of knots and is prone to leaks. The wood doesn’t leave Japan often and barrels are extremely expensive, often up to twenty times the price of American oak barrels.

The actual amount of American oak barrels that are made isn’t really known. But it’s a LOT!
Reportedly, Jack Daniel’s alone fills around 1,000 a day and Jim Beam filling closer to 2,000. Federal regulations dictates that bourbon distilleries can only use a barrel once! So after they have been emptied, the vast majority are shipped to Scotland, to age single malt.

Bourbon is usually aged for around four to six years and produces a robust whiskey. The bourbon new make, is robust and needs the first use of a barrel for balance. Thereafter, the contribution of the barrel is a lot tamer and this is ideally suited to the maturation of the ‘softer’ single malt new make. As single malts need to be aged for decades without ‘over oaking’ the spirit, a used barrel is ideal.

The importance of spirit maturation cannot be denied and we’ve only just scratched the surface here. Obviously, distilling plays a huge part in the production of spirits but the role maturation plays, shouldn’t be underestimated either. It’s hugely exciting to imagine where all these potential possibilities can lead us and whiskey that could be produced.

Other articles about our Whiskey, Rum and Spirits

Our jounal about Whiskey, Rum and our process and how we do it the old fashioned Tennessee way

in the pursuit of the finest handcrafted, premium spirits

dedicated to crafting the finest of American spirits

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