View of the inside of a rickhouse at Buffalo Trace Distillery
Bourbon aging in a warehouse at the historic Buffalo Trace Distillery

Lately, we have been receiving a lot of questions regarding barrels and barrel aging. Let’s take a fresh look at bourbon barrels. The beautiful color of bourbon and many of the complex flavors arrive through the process of aging in a charred white oak barrel. When the clear distillate enters the barrel, it has flavor but no color and very little aroma.

In early America, barrels were a vital part of transport and commerce. Barrels or casks were hands made in many sizes — small casks for gun powder to very large casks for tobacco. Everything from nails to horseshoes to pickles was shipped and stored in barrels. The ability to store salted meats which sailors were dependent on created a need for more barrels. They were needed to store water on the ships for drinking and to prepare the salted beef and pork.

Barrels also had a critical design feature in that they could roll on their side. The design allowed one or two men to move them around in a time where there were no forklifts.

Red oak and other woods were used to make barrels that would hold grain products or other dry goods. Red Oak is not good for liquids, but it was ideal for dry goods because it would allow air to circulate between staves. Red oak was also used to build rickhouses and other distillery buildings because it was pest resistant.

White Oak is used for barrels to hold liquids, including whiskey.   White Oak contains tyloses that will not conduct fluid. Tyloses are membraneous growths that inhibit the porosity of white oak and help make it watertight.

Barrels were not easy to make. No glue or fasteners are included in the construction. Metal hoops and liquid pressure hold the barrel together. The wood selected for barrels must be dried or aged, and this process can take up to 3 years to properly season the wood used to create barrel staves. Many staves are aged in the open air and take on characteristics of the area.  For example, staves aged in Missouri will be different than staves aged in Kentucky.

Picture of four charred barrel staves
Examples of char levels used by distilleries.

In modern days steam is used to bend the staves that make up a barrel. It is highly likely that in pioneer days steam would not always be available. Coopers would use fire to heat the staves, and this could very well be the origin of charring the inside of a barrel. (There are multiple theories on the origin of barrel charring many of which are bourbon myths) Only later was the charring of a barrel recognized to impart maximum color and flavor. Charring the inside of barrels is now standard practice. Each distillery will choose its level of barrel charring, and many add additional levels of seasoning the barrels. Some will toast the staves before charring, and others add toasted or charred oak to the barrels to increase desired flavor profiles.

Once a barrel is filled and stored in a rickhouse or warehouse, the weather then becomes critically important in the aging process. The change of temperatures forces the whiskey into the wood and maximizes maturation. Kentucky is an ideal location for barrel aging because of the four-season weather changes.

Today used bourbon barrels are in demand. Once you could find them easily and inexpensively to use for garden planters or other ornamental uses, now, they are used to age Scotch Whisky, add flavor to Tabasco sauce, craft beers, and even maple syrup. Taking a fresh look at bourbon barrels shows their importance to the bourbon-making process.