Cask Layers and What They Mean
Scotch Whisky spends at least 3 years and a day, maturing in casks. This makes the cask type and quality super important, being where whisky gains many of its flavour compounds from. When looking at a cask up close, multiple layers can be recognised, revealing much about the whisky inside. Some of these layers include toasting and charring, which are key to unlocking those sweeter flavours.
Image Source: Dramdevotees.com What is Toasting?
Toasting casks involves heating up the casks slowly, using a flame, to a gentle toast, which can be identified as a deep brown colour inside the cask. Not only can this impact flavour but it also makes the vessel more malleable so it can be moulded into shape to ensure no leakages. Additionally, toasting activates the oak, awakening the flavour compounds called lignins and vanillins, so that the whisky can absorb these and create a sweeter element to the liquid. This gentle toast means that the sugars don’t have enough time to caramelise but have been activated enough to provide some of these sweeter notes like vanilla and almonds.
WHAT IS CHARRING?
Charring, unlike toasting, is a process of heat treatment where the cask is heated at a higher temperature over a fire for a short period of time (typically seconds).
This heat helps to remove sulfurous notes buried within the wood and activate the sugars in the oak, similar to toasting. However, charring will release a higher level of sugars depending on its char level. When a cask is charred, ‘the red layer’ is formed which is when the sugars in the oak caramelise to create the sweeter lignin compounds. The depth of this layer is dependent on level of char, hence creating differing levels of flavour compounds.
Charring also allows the wood to be slightly porous, meaning a degree of oxidation occurs. When whisky interacts with oxygen, further compounds are produced, smoothing out the rougher edges in whisky.
Furthermore, charring creates charcoal, and this acts as a filtration system, filtering out impurities within the whisky whilst increasing surface area, ensuring additional flavours are absorbed.
Image Source: Behind the scenes of barrel makingCHAR LEVELS
The different levels of char indicate the differing times spent over a fire/heat source.
A level 1 char is held over a fire for around 15 seconds, resulting in a gentle char, imparting a small level of sweet notes whilst keeping the nature of the whisky very present.
A level 2 char is held over a fire for 30 seconds, giving the cask a medium char, helping to release more lignins and vanillins from the oak and is the most popular within the Scotch Whisky industry.
A level 3 char is known as a heavy char, being held over a fire for 35 seconds. This activates the sugars in the oak and releases some spicier and gentle smoky flavours from the cask.
A level 4 char is also known as an alligator char, being held over a fire for around 55 seconds. It creates a texture very similar to an alligator’s skin hence the name, and results in a deeper colour of whisky with a smokier outcome.
