Charring is one of the last steps a barrel undergoes before it’s ready to accept whisky. Coopers create char by setting controlled fires inside preheated and headless barrels. The fires burn the inner surface of the barrel, breaking down compounds like lignin, tannins, and cellulose, while creating a layer of carbon. After 15 seconds to 1 minute or longer, the flame is extinguished. Barrels are charred to a distiller’s exact specifications, falling into one of four designated levels based on burn time—similar to ordering a steak rare (Char No.-1), medium (Char No.-2 or 3), or well-done (Char No.-4). These char levels play a pivotal role in how whiskies age and taste.
Favored Flavors
Thanks to the breakdown of those compounds, whisky aged in charred barrels has prominent notes such as toasted sugar, vanilla, coffee/espresso, barbecue-like smokiness, caramel, and roasted nuts. Different char profiles change which of these notes take center stage.
Keepin’ it Clean
The charred layer consists of carbon, which makes it a great natural filter for the whisky. As the whisky ages, undesirable congeners (flavor-affecting compounds left over from fermentation or distillation) are drawn out of the liquid and attach themselves to the char.
In the Red Zone
Most of the flavors sit in the “red layer,” the section right underneath the char. Liquid stored in deeper-charred barrels takes longer to interact with this layer, meaning the flavors are extracted from the barrel far more slowly. This facilitates a smoother character over long aging periods. Whisky stored in lighter-charred barrels interacts with the red layer much faster, leading to a quicker rate of flavor extraction. This helps jam-pack whisky with sought-after notes over a much shorter aging period.
Level It Up
CHAR NO.-1
BURN TIME up to 15 seconds
It’s often called a “flash char” due to how fast the process is.
CHAR NO.-2
BURN TIME 20–30 seconds
Char No.-2 is also the No.-2 most popular char level, just behind char No.-3.
CHAR NO.-3
BURN TIME 30–35 seconds
No.-3 is the most popular char level among distillers.
CHAR NO.-4
BURN TIME up to 60 seconds
No.-4 is sometimes called an alligator char due to the scaly texture of the wood after it’s extinguished.
Is there a Char No.-5?
There are heavier chars than No.-4, but they’re few and far between. These intense chars almost always introduce very unpleasant soot and coal-forward notes to the whisky, making them both very hard to work with and very unpopular with distillers. In more extreme cases, the wood can grow so soft that the barrel will warp and/or break.
