The process starts with sourcing barrels. Most producers use once-used bourbon barrels (charred white oak, typically from Kentucky distilleries like Buffalo Trace, Maker's Mark, or Four Roses). Port barrels, rum barrels, and whiskey barrels are less common but growing. The barrel condition matters — a barrel that's been sitting empty and dry for months has less residual spirit character than one that's been emptied recently.
Filling and aging: Liquid honey is poured into the barrel and sealed. The barrel is stored in a temperature-controlled environment — ideally somewhere with moderate seasonal temperature variation, which causes the honey to expand into and contract from the wood pores (the same mechanism that flavors whiskey). Most producers age 3-6 months for bourbon barrels; port and rum barrels may go longer because their flavor contribution is subtler.
What actually happens in the barrel: The honey is hygroscopic (it absorbs moisture) and this property pulls flavor compounds from the barrel staves. Vanillin (vanilla flavor), oak lactones (coconut/woody notes), furfural (caramel/nutty), and residual ethanol all migrate into the honey. The honey's natural sugars also interact with tannins in the wood, creating new flavor compounds that exist in neither the raw honey nor the barrel alone.
The honest caveat: "Barrel-aged" has no legal definition for honey. A producer can fill a barrel for two weeks and call it barrel-aged. Some producers add barrel extract or smoke flavoring to honey and label it "barrel-inspired." The best producers are transparent about aging duration and barrel source. Ask questions; genuine aging produces genuine complexity.