Bourbon barrels can be used to produce some really great beers. At Springfield Brewing Company, like many craft breweries, we use bourbon barrels for some of our beers. Our anniversary beer for the last few years has been a fruited stout partially aged in bourbon barrels and our Little Barrel of Nectar is a stout we produce when the stars are aligned using 8-gallon (30-L) bourbon barrels from Woodinville Whiskey. And most recently we aged our Tsarry Night, a Russian imperial stout, in rum barrels to produce Arrghy Night. So my answer below will come from my experience with these beers.
When we purchase freshly emptied barrels they arrive with the bung in place and sometimes wrapped in plastic. We leave these barrels alone until we are ready to use them because nothing good comes from opening these barrels to smell them and “ooh” and “ah” about what will be. Patience is required when you have the barrel in your possession but no beer to put into the barrel.
Let’s talk about the beer for a moment. Beers that are destined for bourbon barrel aging need to have enough girth to carry the flavor intensity of the bourbon. You can surely make a great bourbon beer that is not a monster, but you may need to blend the barrel-aged component in order to achieve a beer with balance. Many brewers have followed the lead of the tinkerers of this style of beer and have chosen big stouts to put into bourbon barrels. This works for a number of reasons, including the compatible flavor hooks between stout and bourbon barrels, similar flavor intensities, and the way strong beers respond to oxidation. I want to hit on these points one by one.
Bourbon barrels may seem rough and gruff on the surface, but they do have lots of nuance. If you are lucky you will have coconut, vanilla and caramel notes from the bourbon barrel marry with the flavor notes of your base beer. This is why, in my opinion, stouts work so well for bourbon beers. Matching the intensity of the beer with the intensity of the barrel is also something to consider. Since bourbon barrels have a loud and dominant voice they can easily overpower the whispers of subtle ales, such as brown ale. This is where blending can be used to temper the boisterous barrel flavor if you desire something more subtle. And then there is oxidation. Barrels are porous and beer aged in wood is exposed to oxygen. So choosing a style that benefits from slight oxidation is something that I strongly suggest until you have a few of these brews under your belt. Chances are you will find that this is the best type of beer to age in your bourbon barrel.
Let’s go back to the barrel. When your brew is finished it is very important that you do nothing to increase the level of carbon dioxide. If you want to chill your brew to drop yeast, do it in an atmospherically vented container like a carboy or a conical fermenter that is not pressurized. To prep your barrel, all you need to do is remove the bung, pour out and reserve any bourbon that resides in the barrel and rack your beer into it. This is where homebrewing and commercial brewing diverge. If you want to leave this bourbon in the barrel there is nothing stopping you. The commercial world brings in tax compliance rules that are involved and, luckily, out of the scope of your question. Most beer aged in freshly emptied barrels will have extracted most of the bourbon notes in about 3 weeks. From this point forward you should treat this beer no differently than green, still beer following primary fermentation except that you will need to add yeast if you plan on bottle conditioning.
Rewind the tape, if you will for a moment. Not all barrels are freshly emptied. Some were used for aging bourbon (or some other variant of whiskey, wine, or spirit) and permitted to dry out a bit. And others were used to age beer once before. What is a brewer to do?
If you have a dry barrel you need to be concerned about leaks and will want to fill the barrel with very hot water to help the wood hydrate, swell and seal. Dry barrels also lack the residual bourbon of wet barrels and the bourbon is pretty darn important when it comes to imparting bourbon flavor. At home you can hydrate your dry barrel and fill that wooden sponge back up with bourbon. Just buy a good bottle of the brown stuff, pour into your hydrated barrel, hammer in a bung and roll the barrel for several days to let the wood soak up the bourbon. You should pour out the excess to prevent overwhelming the beer.
And if you have a barrel that has been used once for beer you probably can use it again and extract more bourbon flavor without any help from a bottle (as described above). This is a good time to barrel age a tamer beer. Or you can use this second run from the barrel to blend with the first run. Barrel aging is not rocket science. It works very well for certain beers and you will produce a great beer if you stick to the fundamentals!