The Life of a Whisky Barrel

All barrels start out the same - as a tree - but that’s where the similarities end. Different types of wood may be used, but generally some wood is better suited for holding liquid, and some are better for holding dry goods. Our focus today, as with every day, is on the barrels made to hold liquids. More often than not, oak is the go to for whisky barrels. The type of oak that you want to use will depend on what you are putting in it. For example, French oak barrels suit aging wine and American white oak suits whisky. We use American white oak for our style of spirits. 

Once the wood type is chosen, the tree is logged and sawed into cants. These cants are dry pilled and left exposed to the elements to season for at least two years. The natural changes in humidity and temperature expand and contract the wood fibers. The more times this happens, the better, because it takes the flex out of the wood and therefore limits the effect of future temperature and humidity changes.

From this point on, the oak cants fall into the hands of the cooper in their cooperage. The coopers trade is one of the oldest registered trades in the world, and the Coopers’ Union is one of the oldest and most powerful unions in the world. The cants are now cured and seasoned and are cut into staves. The cooper selects the staves, raises the barrel, and heats and chars the barrel to form the bilge of the barrel (more on the effect of barrel char in an up-coming blog). Barrel heads are made from straight staves that are fitted with tongue-and-groove joints and secured with dowels to ensure a leak-proof seal. The nearly-finished barrel is then sanded smooth, and the final barrel hoops are driven in place to secure the staves. 

The result is an American white oak brand-new barrel, which goes off to the distillery to be filled with new make spirits. 

Here are some fun facts: first, even though barrels can be used multiple times, the US Coopers Union passed a law many years ago that states that all bourbon must be aged in new charred American oak barrels. This ensured generations of work for coopers in a world that was starting to flavour barrels of different materials. Second, spirits that are put into barrels are called “new make” or “white dog”. This spirit is perfectly clear when it enters the barrel, and 100 percent of the whisky colour comes from the barrel, with the exception of distilleries that artificially colour their spirits with caramel flavouring (which is most Canadian whiskies). Either way, only after the maturation time is it called a whisky.

Going back to the barrel, the barrel is conditioned in the distillery using hot water or steam to swell the wood. Once it is conditioned and proven leak-proof, it is filled with new make and sealed with a wooden bung. There are various sized barrels, but we use 53 gallon barrels in our distillery.

The newly-filled barrels spend a few days in port, being watched to ensure that there are no leaks that need to be tended to. Even a small leak could drain a barrel over many years. Barrels breath through the pores in the wood and a percentage of alcohol is lost to evaporation - as much as 20 percent of the originally-full barrel! This evaporative loss is fondly called the angels’ share. To compensate for this inevitable loss, new make enters the barrels above bottle strength. Every distillery has their own favourite barrel proof - in our distillery, it is 55 percent ABV. This is based on profile of the spirit and the length of time the spirit will be aged. 

Time for another fun fact: at any given time, there are enough barrels aging in Scotland that if put end-to-end, they would reach from Glasgow to New York and back six times!

So now we’ve gone through the process of getting an oak tree into a precisely crafted barrel, filling it with new make, testing it in port for leaks and confirming it is free of them. Now weighing approximately 500 lbs, the barrel is moved to the rick house. This is the start of this barrel’s glorious career as a whisky barrel, a career that may span several generations. A rick house is a building specifically designed to store whisky barrels. Some modern rick houses are climate-controlled to try and control the maturation process. Like some other rick houses, ours is not heated nor cooled and does not have controlled humidity levels. The natural heating and cooling of the seasons, along with the natural humidity changes, forces the alcohol into the wood in warm weather and extracts it in cold weather.

Now, a little bit about the timeline. The oak tree was about 80 years old. The sawed cants were seasoned for two years, constructed into barrel, sent to the distillery, filled, and were tucked away in the rick house. Let’s say this took a year. The barrel is now going to have a big sleep, for another ten years, to produce a 10-year-old unpeated single malt. Throughout the tail end of the maturation period, the barrel is sampled, a treat usually enjoyed by the distiller and distillery owners. In our example, we now have a 10-year-old whisky that is drained, bottled, and enjoyed. 

By now you might be saying, wait a second, you said that this barrel was entering a career that may span generations, but we’re only at 93 years since that barrel was an acorn. Well, I wasn’t kidding. If this barrel was ageing American bourbon, it would not be used again, but that doesn’t mean that it cannot be used to age other spirits. Once-dumped bourbon barrels are sent all over the world to be used for ageing all sorts of other whisky’s as well as rums and brandies. Most scotch is aged in one-dumped bourbon barrels. 

So once the barrel completes its first cycle with bourbon or another spirit, it is checked over, tested for leaks, refilled, and the cycle continues. The barrel may stay at the same distillery or shipped around the world. This barrel may be filled with spirit that is slated for a 10-year maturation period or 15 to 25 years. The big question is, how many times can this barrel be dumped and refilled? That all depends on the barrel. If it is a well-built top-quality barrel, it may be refilled three or four times - roughly 100 years of service. 

Sadly, every barrel has its own limitations, and can only contribute so much to a spirit. At some point it becomes played out. Does that now make it firewood? Well, consider this: that barrel is made of staves that are close to a half-inch thick, and the alcohol has not penetrated all the way through. Instead, it may have only penetrated the oak about one-eighth of an inch. That means that the barrel can be taken apart hoop by hoop, stave by stave, and planed down on the inside to expose fresh wood. 

Disclaimer: if you take out too much spent wood, the integrity of the barrel will be compromised and it will no longer be usable. 

So assuming you still have usable staves, the barrel can be reconstructed, with each stave being placed in the same spot on the barrel from which it originated all those years ago. Before the heads are replaced, the barrel is charred again to the char level that the distiller has specified. The reconditioning process is usually done by coopers, sometimes on-site in a cooperage owned by the distillery or, in our case, by the distillery owner. This is not to say that I think I am a cooper, or that I have nothing better to do, but because we live in the middle of nowhere and don’t have a cooperage anywhere around, this job falls to me. 

After reconditioning, the barrel can go back into service. It’s interesting to note that a reconditioned barrel or a barrel that is close to being played out is very useful for ageing spirits that need only a light contribution from the barrel. For example, rum must be aged for two years, legally, but if you’re producing a light amber rum, the barrel contributions can be minimal to reach your end goal. 

So what happens to our barrel once it has been played out and rebuilt multiple times to the point of being too thin to be structurally stable? Is it then firewood? Perhaps, or perhaps not. Totally-spent barrels go on to finish their careers as oak furniture or are chipped up for use in oaking wine, or even used in smokers to smoke meat. 

People say that the whisky industry is environmentally irresponsible for cutting down an 80-year-old oak tree just to make barrels. The truth is that oak will be in service for just as long as it takes to grow another oak tree - perhaps longer. 

So that is the life of a whisky barrel. Wooden barrels have a fascinating history, and serve a mind-boggling purpose in the spirit and wine industry. The scientific world has spent countless years trying to unlock the secrets of an oak barrel, even though scientists have discovered some amazing things, this is one mystery they still haven’t solved.

Here’s a trivia question for you: who discovered ageing whisky in oak barrels, and how did they discover this natural phenomenon? Tune in to our next blog and we will answer this question and discuss what actually goes on inside of a whisky barrel during the ageing process.

-Tim Karchut