This post is part of our Scotch Hub.
Whiskey, by law, can’t be called “whiskey” until it has spent some time maturing in a wood cask. But beyond just playing a role in adherence to regulations, that cask is believed to provide up to 80 percent of a whiskey’s final flavor—and all of its color. As a result, the importance of casks in the production of whiskey simply can’t be understated—they’re essential.
So we’re paying homage to these hardworking vessels with our Whiskey Casks 101. If you want to skip straight to the infographic, scroll down. Otherwise, let’s dive in.
Whiskey Barrel or Whiskey Cask?
The correct generic term to reference a cylindrical wooden container used to mature whiskey is whiskey cask. A whiskey barrel is a specific type of whiskey cask, with a specific shape and volume capacity.
There are many types of whiskey casks, but technically there is but one type of whiskey barrel—the American Standard Barrel, otherwise known as a bourbon barrel.
These days, it’s common to hear people use the term “barrel” interchangeably with “cask”. Though technically incorrect, it’s generally accepted and understood, particularly here in the States.
How Is a Whiskey Cask Made?
Casks are made from quarter-cut wood staves, typically from American or European white oak. These staves are then assembled in a temporary steel rig to hold them in place, with a even distribution of wide and narrow staves. Hot steam is used to help shape the staves, and thick steel rings are added to the ends of the cask to complete its shape.
Casks are then often toasted—the inside is heated to certain temperatures—to help bring the wood’s natural sugars to the surface, where it can interact with the liquid that will eventually fill that cask. The toasting is followed by a charring process—where the insides of the casks are burned with an open flame—for a shorter period than the toasting, but at a much higher temperature. Charring yields flavors including vanilla, spice, and smoke, and produces a layer of charcoal on top of the wood. This helps to filter out unwanted flavors and congeners, and smooth out some of the liquid’s rough edges.
The whole cask-making process is a bit more complex than our simplified summary. If you’re interested to learn more about how casks and barrels are produced, whisky.com has a great piece on barrel production.
Can Whiskey Casks Be Reused?
Whiskey casks can indeed be reused. Different producers will have their own rules about which casks to reuse and how often, and it is very common to see whiskey maturing in used casks, picking up characteristics of the previous occupant.
Bourbon law, however, requires that all bourbon be aged in new American oak barrels. This first use of a new barrel is called “first-fill.” With bourbon demand and production skyrocketing, you can imagine the vast quantity of once-used bourbon barrels that get discarded with every production cycle in order to make room for new barrels.
Fortunately, there is a thriving secondary market for these ex-bourbon barrels. Many scotch whisky producers, as well as other spirits industries like tequila, will age their products in ex-bourbon barrels. Wood that has already been used for many years in the bourbon trade will go easier on the new liquid inside it, which means those scotches and tequilas won’t soak up so much of the cask’s characteristics. In the case of scotch, it’s common for ex-bourbon barrels to be used multiple times, and considering the diminishing power of that wood, the scotch can be aged for long periods of time—even decades—without becoming overly influenced by the oak.
How Does a Whiskey Cask Work?
What exactly does a cask do to impact a whiskey so much? And why are there so many different types of casks, and of varying sizes, used around the world?
For starters, the wood of a whiskey cask is porous, which allows air to pass through the cask and contact the spirit inside. The air itself may impart flavors into the whiskey based on the environment—called terroir. An example is Islay scotches, which are aged in the salty sea air. And, as noted above, the wood will impart its flavors into the spirit as well.
How long a spirit rests in a cask to mature, how warm or cold the temperature is inside and outside of the cask, how dry or moist the humidity is where the cask is stored, and many other factors play into the overall profile of the whiskey and the flavors it picks up.
Also, size matters! Different sized casks will have different effects on the maturation of a whiskey. Smaller casks tend to accelerate the aging process, due to a higher liquid-to-surface ratio.
Whisky Casks 101: The Infographic
To help you better understand the role whiskey casks play in the production of whiskey, as well as visualize the wide range of cask types and sizes that are used, we created this handy infographic.
Click to enlarge the image, save it to a PDF, print it out, share it with friends and fellow whiskey enthusiasts, or hang it on your wall so you can stare at it while having a dram. Cheers.
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