Barrel aged

In the style guidelines, barrel aged is not a style with fixed characteristics, but a treatment you can apply to any beer. The Brewers Association describes 'Wood- and Barrel-Aged Beer' as any traditional or experimental beer, lager, ale or something in between, that has been aged in a wooden barrel or with wood. For colour, flavour, bitterness, body and alcohol it says each time: 'varies with underlying style', it depends on the base beer.

The BJCP, too, in categories 33A and 33B, makes all the figures depend on the base beer. Anyone entering a competition has to state the base beer or a description of the beer, plus the kind of wood or barrel.

In practice it is mainly strong, full beers that go into barrel, because those can best handle the extra flavours. Strong stout and barleywine are well-known examples. That is why this page sits under 'Dark & Creamy'. But a barrel-aged light or sour beer tastes very different.

The Brewers Association literally writes: 'Wood-aging does not necessarily impart wood flavors, but does result in distinctive sensory outcomes.' Ageing on wood therefore does not necessarily give a wood flavour, but it does give a character of its own.

What you taste depends on the barrel. The BJCP distinguishes beer on wood without the flavour of an earlier drink (33A) from beer on barrels that previously held whiskey, bourbon, rum, gin, tequila, port, sherry, madeira or wine (33B). Only in that latter case should the character of that drink be noticeable, and even then in balance.

Toasted or charred wood can give notes of vanilla, caramel, toast, nuts, coffee or cocoa. Tannins from the wood can make the body fuller and the finish drier. According to the BJCP, the wood flavours should support the base beer, not dominate it.

The barrel itself matters too: a bourbon barrel that is being filled for the second or third time gives off less bourbon aroma, according to Brew Your Own.

The BJCP calls ageing on wood a traditional method, with oak casks and barrels as the tradition. With sour styles such as Flemish red and lambic, wood ageing is part of the style itself.

But deliberately putting beer into used bourbon barrels has only been usual since the mid-1990s, according to beer writer Jeff Alworth. A well-known origin story is an imperial stout from Goose Island in Chicago. The brewery says 1992, but according to Alworth that was the brewer's own estimate and it was almost certainly 1994. Journalist Josh Noel arrives at 1995. Andy Crouch of All About Beer also writes that it was not the first beer in bourbon barrels: according to the brewer himself, the whiskey-barrel-aged Triple Bock from Boston Beer Company, first released in 1994, was the inspiration. Who was first is therefore disputed.

Why are there so many bourbon barrels? Under American rules, bourbon has to age in new, charred oak barrels. A used barrel therefore cannot serve for bourbon again.