charred barrels

Charred barrels are wooden casks, typically oak, whose interiors have been burned before use in aging spirits.

The charring process caramelizes sugars in the wood and creates a layer of activated carbon that filters impurities while imparting flavors of vanilla, caramel, and smoke to the liquid inside.

American bourbon legally requires aging in new charred oak barrels, which are then often sold to Scotch whisky and other spirits producers for secondary use.