Beer’s relationship with wood goes back hundreds of years, since it was the only reasonable option for bulk storage prior to the adoption of stainless steel. When we think about wood today, though, it’s almost always in the context of adding extra complexity to beer, especially high gravity ales.
At homebrew scale, true wood barrels are often far more trouble than they’re worth. They are expensive, require special care to prevent leaks, and aren’t always available in a convenient size. Wood also loses much of its character after a few uses, requiring longer contact times to impart the same amount of flavor. I don’t bother with barrels for these reasons, but I’ve settled on an alternate method that works well enough that it’s won multiple medals at state-level competitions.
It starts by purchasing a ¾ inch (2 cm) oak dowel rod from a hardware store. Ensure it is untreated wood. Cut it into ½ inch (1.2 cm) lengths. Depending on what kind of flavor you want from the wood, the next step is to toast it. This can be done by spreading the pieces on a baking sheet in the oven for 60 minutes (250°–500°F (121°–260°C), depending on the level of toast) or holding them over an open flame. Bourbon barrels are heavily charred on the inside before use, so if this is the effect you’re after, an open flame (outdoors!) is your best choice.
Spirit barrels, especially bourbon, are a popular choice for wood-aging beer, especially imperial stouts and barleywines. In Kentucky, bourbon is aged in the barrel within rickhouses. These are large, multi-story buildings that are not climate-controlled. They get hot in the summer and cold in the winter. Wood expands and contracts with changes in temperature. The bourbon seeps into the wood when it’s hot and is squeezed out when it’s cold. You can fake this on an accelerated timeline at home.
Put the wood into a glass jar with an airtight lid. Pour in enough bourbon to cover the wood. Every 12 hours, move it in and out of your freezer. I usually leave it on the counter overnight, then put it back in the freezer in the morning for the day. Do this for a week or two and the wood is ready to add to a fermenter. I’ve had success with 2–3 months of aging. You can reuse the wood, but as with barrels, it will take longer to get the same character in the next batch.