How Barrels are Made and Why It Matters

We take our barrel aging very seriously here at McClintock and had a chance to visit our cooperage in Minnesota recently to see some of our newest batch of barrels being made. Barrel aging whiskies is one of the most important parts of what gives a good whiskey it’s flavor. We thought we would take everyone through how each individual barrel is made for us and answer some of the most common questions we get here at the distillery about barrel aged whiskies.


What does a barrel do for whiskey?

We teach a 4 hour course on what exactly happens to whiskey as it ages in the barrel, but in a simple term barrel aging makes a whiskey better. There are three chemical processes at work that we look for in each one of our barrels. Subtractive reactions- Where undesired compounds either evaporate out of the barrel as it breathes, or get “filtered” out as spirit passes through the carbon in the charcoal. Additive reactions- Where flavors from the wood (vanilla, caramel, oak, leather, charcoal, smoke) seep into the spirit and gives it a “classic whiskey” flavor. Reactive Mechanisms- Being barrel aged actually chemically alters compounds and changes them into beautifully complex aldehydes and aromatic compounds that gives whiskey bouquet and lends to the mature notes that you want.


What are barrels made of?

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Barrels can be made of any wood, but Rye’s and Bourbon’s have to be made using charred white American oak. Even within this one species of oak, where the wood is grown matters in a big way. We use Minnesota grown oak, because of the shorter growing seasons, the rings are tighter and there is more delicious lignins (the sweeter notes in whiskey) unlocked when the wood is charred. Oak grown in Missouri will taste completely different than the same tree grown in Montana. Just like grains, every aspect of the environment matters when selecting wood to use for a barrel.

How is a barrel made?

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It is truly and art form to hand craft barrels and it is wonderful to see with the rise of the craft distillery movement, the cooper trade is coming back in a big way! It takes years to become a master cooper and with good reason. The wood is first seasoned, either in a kiln or out in the yard, for some period of time (2 years preferable if possible). This lets the “green” components of the wood evaporate and dry out so that you are left with desirable compounds for the finished barrel. Once seasoned, the wood is milled and shaped for the barrel. Shorter pieces are fashioned into heads, while the best pieces are shaped into staves, which are the long slats that run horizontally on the barrel.

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After the wood is shaped, the cooper grooves the wood for the head and fits them together by hand. The staves are then ordered and placed into holding rings to start the barrel shape. At this point the wood is toasted to make the wood malleable and the ring is hammered down on the opposite side. Once it has the barrel shape it is charred over flame to the desired char level. The heads are inserted, the holding rings come off and the finished bands go on. The barrel is pressure tested and ready to go!

The whole process is still very hands-on and a truly incredible thing to witness. A good cooper doesn’t use glue, wax or any other adhesive and most barrels are held together with pure craftsmanship.

Why char the barrel?

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A question we get all the time, especially from our brothers across the sea in Europe. Charring barrels is a very American tradition and originated here. Think of the structure of wood as a wall made of bricks (cellulose). The wall itself is held together is used for structural purposes, but each individual brick (simple sugars) are delicious and flavorful on its own. By exposing these cellulose chains to fire, we break down the structure and expose simple sugars that can easily impart sweet flavors on the whiskey. The deeper the char, the more of these lignins and polyphenols are exposed and can be unlocked into a whiskey.

Why does whiskey need to be aged for so long

Whiskey doesn’t need to be aged to be good, but a lot of the complexities and flavors that we desire in whiskey just take time. Extractions from wood are dependent on surface to volume ratio, so if you age whiskey in a 1 gallon barrel it will pick up flavor from the wood a lot faster than if you use a 30 gallon barrel. However, the reactive mechanisms just take time and oxygen. Some of these reactions really can’t begin to take place until 8-10 months so we are of the mindset that it just takes time to make a good whiskey. Not that short aged whiskeys can’t be good, but for a classic and complex whiskey it really just needs time in the barrel. Many of these reactions are oxygen dependent so it is really incredible that 400 years ago we happened to be using wood containers that were able to “breathe” and allow oxygen into the spirit as it aged. This is the reason that if you are aging spirits in a completely sealed container you will never get the same complexity as you do out of a classic wood barrel.

For more info on barrel aging check out our comprehensive distilling classes

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