How Are Whiskey Barrels Made?

Every whiskey fan is well aware of the fact that producing distinguished, fine, and flavorful whiskey is a process made up of a multitude of different steps, stages, and processes… and what’s more, it’s practically impossible to proclaim that any one is more or less significant than the other. 

 

After all, in order to achieve perfection in the glass, and in order to get those aromas and flavors singing on the palate, so many unique and time-honored factors need to be considered. These range from the terroir in which the grain is cultivated (that’s right: terroir is important to whiskey, and not just wine!), to the air quality, the type of spring water used, the distillery equipment, the size of the stills, the vision of the distiller… and the list just goes on and on and on. 

We’re going to be taking a look at one of the most misunderstood, under-appreciated, and yet significant and impactful aspects of whiskey-making: the crafting of the cask. 

Whiskey Barrels Through the Ages

Many of the aspects of whiskey production haven’t much changed over the centuries, and this is definitely true for cooperage, or the production of whiskey casks and barrels. While the fundamentals have more or less stayed the same for hundreds of years, it’s fair to say that the art of the cask maker has been gradually, yet significantly, refined over the past millennium… leading to the incredible results you’d see on any decent whiskey tour today. 

 

 

That’s not to say that cask-making has been on a constantly-evolving journey towards perfection - indeed, you can look through the whiskey history books and find all kinds of misfires (notably the ridiculous collapsible shipping casks of the 18th century, and the cask cleaning engines of 1803!). The hiccups were just a step on the journey of what cask making really is: a remarkable blending of science and art and a key stage on the path from field to glass. 

The 6 Stages of Whiskey Barrel Making

Casks are, and have always been, made by coopers; highly trained artisans who are experts in shaping wood and making barrels, and whose job involves carefully understanding the specifications and visions of a distillery, and using their skills to help them achieve a specific style and character. 

This might involve a wide number of processes: for example, the distiller might call for a smokier, woodier flavor, which may see the cooper decide to lightly char the wood after forming the barrel. They might want the unique flavor of European oak or the freshness and vanilla touches of American oak. They might want small barrels with intense wood flavors, or massive ones for long-term aging and subtle influences. The cooper will take all of these requests on board, and utilize their time-honored talents to make them happen. 

 

 

Let’s take a closer look at the art of cooperage, and consider how the stages of barrel making impact our favorite whiskeys. 

1. Sourcing the Wood

As is commonly known, oak is by far the number one wood in cask and barrel production. While there are other woods that are sometimes used, oak is favored for a whole range of reasons, and it isn’t just a matter of sticking to tradition: oak is bursting with tannins and flavor-packed chemicals, meaning there will be plenty of expression in the whiskey. What’s more, due to the way that it grows, oak provides the perfect level of oxidation (the slow seeping of air) in the barrel, which ages and matures the whiskey at the right pace.

Most coopers will insist on a seventy-year-old (or older) tree for use in cooperage, as this ensures the right grain. Terroir is important too - over the decades, the tree will pick up on some of the flavors of the land on which it grows… there really is a lot to consider when sourcing oak for cask making!

2. Cutting the Staves

Once the wood has been selected and the tree has been chopped, the oak logs are carefully cut into very long, very thin, and seemingly very delicate pieces, which are then dried in natural sunlight for a period of many years. This slow drying process not only reduces the moisture in the wood (which is necessary for a whole number of different reasons), it also controls the presence of tannin, which needs to be reduced in order not to impart too much astringency in the resulting whiskey. 

Coopers need to be extremely meticulous in how their wood is cut, as trees contain unique pathways within their trunks, which allow for the healthy flow of water and nutrients from the soil. Cutting along these pathways will increase the likelihood of the wood splitting or leaking. Once dried (a process known as ‘seasoning’) the thin planks are cut into shorter staves, which will form the sides of the barrel or cask. 

3. Assembly and Toasting

Once the staves have been cut from the seasoned oak, they will be assembled around a single hoop of iron. The resulting structure is known as a skirt, and this can then be bent and shaped to form a barrel or cask, depending on the size. This process is usually carried out over an open flame, which toasts the wood to lend it character and to activate the oils and flavonoids. Furthermore, the toasting process also caramelizes the sugars which are naturally present inside the oak, and this lends many whiskeys their most prominent sugary, molasses, and toasted nut flavors. Some coopers will heavily toast the skirt, others will use a lighter touch - it all comes down to the distiller’s preference and the flavors and aromas they most want to achieve in the bottle. 

4. Fitting the Hoops

After the toasting process has achieved that perfect balance of smokiness and sweetness, and the skirt has been bent into the correct shape, a further series of metal hoops are added, allowing the distinctive cask shape to be achieved and fixed. The hoops enable a continuous and consistent pressure to pass through the staves, something which ensures the barrels maintain their form and do not warp or split. 

5. More Fire is Applied… If Necessary

At this point, the barrels heading to wine and sherry cellars are finished and shipped off, ready for the next stage in their long journey. However, if the casks are destined to be used in Bourbon production, they’ve still got another process to go through the charring.

By law, bourbon must be aged in newly charred white oak casks - it’s essential for maintaining that unique and distinctive bourbon style. The additional toasting creates a fine layer of ash and carbon which coats the cask, lending more flavor, and acting as a natural filter to remove impurities from the whiskey. 

6. Finishing the Barrels

After all that chopping and toasting and shaping, we’ve finally reached the end of the cooperage process - a practice that has been perfected over thousands of years! The final stages involve fitting the cask heads (the parts at either end of the barrel) which are sealed to keep the whiskey inside. The final hoops will be fitted, and a bunghole will be drilled, which allows the whiskey to be poured inside. Once all of this has been done, and the cooper is satisfied with the work, the finished barrel is all ready to be filled with a brand new whiskey… and then it’s time for it to be squirreled away in a cellar for a minimum of three years, and that’s where the magic of maturation begins to take place. 

There you have it: the six artisanal stages of barrel making! Let’s give some real appreciation to the master craftsmen behind this amazing process, and raise our BrüMate glasses to those who put in the time, effort, and skill to help our whiskey become the incredible drink that it is. Here at BrüMate, we really love finding out about this kind of thing. Why? Because our temperature-controlled glasses display a mastery of their own and look amazing while offering the perfect drinking experience. Try yours today!