Charring and Toasting – both impart flavour to a spirit but do you know the difference between a charred and a toasted cask?
Whisky / Whiskey derives most of its flavour from the oak casks in which it is matured. The interior of the casks undergoes a heat treatment which contributes to the flavour profile of the new make spirit. There are two options for applying this heat to the inside of the barrels, a fast short burn (charring) and a longer gentle heat (toasting).
Charring a process that can be described as a fast burning of the inside of a cask where the intense heat results in burnt appearance. The interior of the cask turns black with a charred residue that acts as filtration and removes some undesirable flavours such as sulphur.
The intense heat caramelises the sugars in the oak which imparts a sweeter flavour along with caramel notes, vanillins and some tannins along with a deep and dark colour to the spirit.
Charring also allows a deeper penetration by the spirit and it’s that intense interaction with the oak that gives it more flavour. Charred casks impart vanillin flavours, smoky notes, caramel, honey and spice.
Char levels refer to the length of time the interior of an oak barrel has been exposed to an intense heat source. The Bourbon industry generally uses four types of char:
Level 1 Char—15 second burn; imparts modest amount of oakiness from the cask.
Level 2 Char—30 second burn; imparts a more pronounced sweetness.
Level 3 Char—35 second burn; imparts a more spicy and earthy flavour profile, a deeper colour, vanilla and caramel notes.
Level 4 Char—55 second burn; also referred to as “alligator char,” as it produces a texture similar to an alligator’s skin; imparts a deep colour and a spicy flavour profile.
Compared to charring, toasting is a slower process where the barrels are heated gently which results in the oak having a dark brown colour rather than a blackened char. The slow and gentle burn means the sugars in the oak do not have enough time to caramelise. As such, the spirit is lighter in colour and not as sweet as one from a charred cask.
Toasted casks impart some nuttiness, light vanilla flavours, and some sweet notes akin to a light caramel and toffee.
Cask Charring and Toasting
In summary, cask charring is a fast burn which imparts vanillin flavours, smoky notes, caramel, honey and spice. Cask toasting is a slow, gentle burn which delivers lighter flavours of vanilla, nuttiness and toffee.