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How To Age Whiskey: A Complete Guide

How To Age Whiskey: A Complete Guide

, by Scott Connor, 11 min reading time

Understanding how to age whiskey can produce a well-rounded spirit that is sure to be enjoyed by all. Read on to learn our complete guide on aging whiskey. 

How To Age Whiskey

Premium, aged whiskey is one of the few spirits that needs no additions. The smooth, refined flavors of matured grains and the unique woody notes bestowed by the aging barrel are best sipped unadulterated.

Nothing against a pour of cola, but when a spirit has been waiting decades to be drunk, it deserves your full attention. 

What is it about whiskey’s long aging journey that makes it so uniquely powerful and delicious, however?

Luckily, learning the essentials of how to age whiskey doesn’t take as long as the maturation process itself. Pour out a finger of your finest to nip at, we’re cracking open the distillery cellar to learn what’s really going on inside those barrels.

Before the Barrel: When Bourbon Was a Baby

Before you can age whiskey, you must produce it. The journey whiskey undergoes before it even reaches the oak barrel is a complicated topic on its own. Much like the aging process as a whole, however, you can smooth out its harsher notes.

So, what is whiskey made from exactly? 

Three simple ingredients comprise whiskey: grains, water, and yeast.1 

Different distillers elect to use different types of grains, and may even mix multiple in the production of a single whiskey. The four most popular cereals for whiskey production and their associated final products are:2

  • Corn (Bourbon)
  • Rye (Rye… understandably) 
  • Barley (Scotch)
  • Wheat (Wheat whiskey)

Grain choice influences the flavor and look of the final product. After selecting their grains, the distiller will boil them with water, inoculate the resulting juices with yeast, ferment them, then distill it all, usually multiple times.1 Once whiskey reaches this stage in its life cycle, it's ready to be locked away for aging and future enjoyment. 

Sip. Savor. Repeat. Your perfect whiskey awaits. Shop Whiskey!

Choosing a Cask: What’s Behind the Barrel?

Whiskey is aged and stored in wooden barrels. This has become so ubiquitously known, that it’s nearly impossible to find a trendy brewpub these days without using one as a table. But those big barrels aren’t just for eating overpriced hamburgers, they actually serve a major purpose in the whiskey production process. They imbue the spirit with the flavors and colors that excite our palates.

On a chemical level, this means sugars locked inside the fibers of the barrel’s wooden hull are freed up by the alcohol within. These sugars leech into and infuse with the whiskey, changing its chemical composition, flavor, and mouthfeel.3

The kind of wooden barrel a distiller chooses has a major impact on the final outcome of their spirit. Each small barrel possesses unique qualities that are imparted onto the aging whiskey, and no two barrels are exactly the same in composition or effect.4

Aging Whiskey

What Are Whiskey Barrels Made From?

Oak is the distiller’s wood of choice when selecting whiskey barrels. In fact, production laws in some of the world’s most whiskey-loving nations, including the USA5 and Scotland,6 mandate aging in oak.

But the choice of wood doesn’t tell the whole story.

To begin with, there are around 500 species of oak trees worldwide, each with its own unique qualities and characteristics.7 Not to mention, distillers employ transformative techniques when preparing barrels to achieve the tastes they are aiming for.

Aging in Used Barrels

Some distillers specifically select barrels that have already been used to age other spirits. Liquors not only gain a barrel’s qualities while aging, but also scrawl their own stories on its woody walls. A well-seasoned barrel will imbue an aging spirit with irreplicable qualities that new casks can’t match.8>

Some common spirits to source barrels from include:

  • Sherry – Noted for its ability to mellow out grain’s harsher notes and add a touch of fruitiness to the body of whiskeys.8
  • Bourbon – Previously used bourbon barrels are a hot commodity for aging other styles of whiskey, particularly scotch. 
  • Powerfully sweet wines – Portuguese Port and French Sauternes, both noted for the sugary sensation they leave on your tongue, produce barrels highly touted for their use in whiskey production.8

While used barrels bestow unique qualities onto the liquor within them, they aren’t the only way to add flare to an aging whiskey.

Changing Things Up with Char

Some distillers will even spark up a fire and char their barrels in preparation for whiskey storage. Burning the barrels opens up the wood's pores, causes the oils inside to sweat out, and exposes the whiskey to more of the oak’s essence.9

The longer a barrel is set aflame, the deeper the flavor and aroma it imparts onto the liquid within. There are 4 general levels of char that whiskey-makers use to prep their barrels:9

  • Level 1 – 15 seconds aflame
  • Level 2 – 30 seconds aflame
  • Level 3 – 35 seconds aflame
  • Level 4 – 55 seconds aflame

Distillers choose how much or how little char is suitable for the results they’re looking for in their final product. Different types of whiskey call for different approaches to distillation and aging—and different amounts of fire.

Understanding what type of whiskey a distiller is aiming for can give us a better understanding of how they select their cask.

Aging Whiskey

Different Approaches to Aging Different Whiskeys

Now that you know the answer to does whiskey age in the bottle, let's look at the different aging techniques. Different styles of whiskey have unique aging techniques, often dictated by both tradition and law. Even amongst the same type of whiskey, however, there are huge variations in distillers’ different approaches to maturation.

Regardless, common sense and legal requirements produce some basic guidelines for a whiskey’s aging journey.


While heavily associated with the American South, bourbon can be legally produced anywhere within the United States. To be considered bourbon, it must spend at least two years in charred oak barrels that have never been previously used.10 

The level of char distillers apply to their barrels is directly related to the intensity of flavor imparted onto the final product. The longer a barrel spends burning, the more oaky and earthy you can expect the bourbon to be.9 More time spent in the cask leads to richer and deeper tastes and aromas upon bottling as well. 

Twenty-four months is just the law’s bare minimum. Some larger distilleries, like Jack Daniels, employ professional tasters that sample spirits and decide when they’re ready, rather than relying on time alone.11 Many ultra high-end bourbons, such as Buffalo Trace’s Willam Larue Weller, don’t enter the bottle until they are in their teens.


Like genuine Bordeaux and Champagne, real Scotch can only be produced in the land of its namesake. 

Scottish law requires aging for three years inside oaken casks, but doesn't stipulate that they need to be new.12 These looser laws mean Scottish distillers have more freedom to hold their liquor in pre-loved containers than their American counterparts. 

Used bourbon barrels are a premium choice for high-quality scotches like Glenfiddich’s 14 Year Reserve. Recent reforms mean a wider range of previously used barrels, such as those used to age tequila, mezcal, and China’s national spirit, baijiu, may soon be housing Scotland’s maturing whiskey.13 

Other Styles of Whiskey

Rye and wheat often get mixed in, both legally and physically, with other grains in the production of blended whiskeys. In Canada, whiskey is nearly synonymous with rye, which must legally be aged three years.14 Laws don’t limit distillers to oak, but tradition and logic still make it the usual choice. Carefully selecting barrels with a specific flavor and aroma profiles can recreate tastes such as apple without chopping down the family fruit tree.

While style determines a lot of the aging process, it’s up to the distiller to pick the correct barrel for the job. 

That said, sometimes, it’s too difficult to decide on just one.

Multi-Barrel Aging

While there are laws that dictate how long whiskey needs to spend inside a specific cask, there is often none governing where it must go after its initial bout of aging. 

One common tactic distillers use is aging in specific barrels to meet minimum legal requirements, then switching to others to change up flavors. 

Often, whiskeys will be aged in their original oak casks and then finished for a short amount of time in a used wine barrel. Doing, so levels out bitter, astringent flavors and adds a fruity, herbal touch to the final product.8 

Many distillers get creative with cask combinations to enhance the fruits of their labor. Experimenting with different barrels produces unique whiskeys with notes that can’t be hit by single-barrel aging.8 

With how long it takes for whiskey to age, however, the experimentation is best left to the professionals. 

Don’t Wait Years to Age Your Whiskey, Get it Delivered Now from Barbank

You’ve cleared out your basement, secured a gargantuan oaken cask that once housed Sherry, and have a bread factory’s worth of grain at your disposal.

What you don’t have, however, is several years to kill before tasting great whiskey or figuring out how to store whiskey properly

So set your bottle of Glenlivet out on your antique-barrel tabletop, because there’s no need to wait for premium whiskey with Barbank.

Online liquor delivery is at the tips of your fingers, with thousands of bottles to choose from. Barbank carries elite whiskeys for sipping neat during moments of refined indulgence and the perfect companions to mixes and sodas.

Don’t let a lifetime slip by waiting on fine whiskey. Even if it stops aging once it's locked in the bottle, we don’t. Order your favorites online today, and if anyone ever asks, “how do you age whiskey?” simply say, “I don’t, I get mine from Barbank.”


  1. Discover Scotland. Whisky Production. https://traveltrade.visitscotland.org/content/pdfs/fact-files/4030746
  2. Lux Row Distillers. Whiskey 101: A Quick Guide to Grains. https://luxrowdistillers.com/whiskey-grain-guide/
  3. National Library of Medicine. Liberation of recalcitrant cell wall sugars from oak barrels into bourbon whiskey during aging. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6203734/
  4. University of Kentucky. Sources of variation in bourbon whiskey barrels: a review. https://www.researchgate.net/publication/352442235_Sources_of_variation_in_bourbon_whiskey_barrels_a_review
  5. Talks on Law. Bourbon as Defined by Law. https://www.talksonlaw.com/briefs/bourbon-as-defined-by-law
  6. Scotch Whisky Association. Q&A: Scotch Whisky Technical File. https://www.scotch-whisky.org.uk/insights/protecting-scotch-whisky/qa-scotch-whisky-technical-file/
  7. One Earth. Oak Trees: Kings of Biodiversity. https://www.oneearth.org/oak-trees-kings-of-biodiversity/
  8. Grapes and Grains. The Influence of Casks and the Science of Whisky Aging. https://www.grapesandgrains.org/2017/05/the-influence-of-casks-and-science-of-whisky-aging.html
  9. Tales of the Cocktail. What You Need to know About Barrel Char: A Primer on Four (Increasingly Hot) Levels. https://talesofthecocktail.org/techniques/what-you-need-know-about-barrel-char-primer-four-levels/
  10. Tax and Trade Bureau. Statements of Age. https://www.ttb.gov/images/pdfs/spirits_bam/chapter8.pdf
  11. Jack Daniels. Maturation. https://www.jackdaniels.com/vault/maturation
  12. Scotch Whiskey Association. Legal protection in the UK. https://www.scotch-whisky.org.uk/insights/protecting-scotch-whisky/legal-protection-in-the-uk/
  13. Robb Report. The Scotch Whisky Association’s New Barrel Rules Could Change the Spirit’s Future. https://robbreport.com/food-drink/spirits/scotch-whiskys-new-rules-could-change-the-future-of-barrel-aging-2870985/
  14. Government of Canada. Canadian Whiskey, Canadian Rye Whiskey, or Rye Whiskey. https://laws-lois.justice.gc.ca/eng/regulations/C.R.C.,_c._870/section-B.02.020.html