
The Journey From Barrel to Bottle
Whiskey Barrel Aging
The barrel has been an icon throughout the history of whiskey. At Jameson, we even have our Barrelman emblem embossed on every bottle.
Barrel aging is integral to whiskey creation, and a key part of developing a whiskey’s character. But why is whiskey aged in barrels? What does barrel-aged even mean?
Luckily, our experts in Midleton have the answers, so let’s learn what it’s all about!
How Is Whiskey Aged?
Aging whiskey means leaving newly distilled spirit to sit in a sealed wooden vessel for a long time – often years.
The History of Barrel Aging
For thousands of years, wooden barrels were used to store and transport all types of liquids and food. A recently distilled spirit would have been poured into a barrel, sealed, and put on ships bound for elsewhere or kept in cellars.
This method was designed to store spirits for long periods, so, naturally, there were barrels that weren’t opened for years. And, when they were, the clear spirit that entered these (often) oak barrels emerged as the beautiful amber liquid we know as whiskey.
Barrel Aging Today
Today, whiskey distillers the world over age their product in barrels to impart flavor and color. The exact aging process depends on the whiskey. For Jameson Original, once the spirit is distilled, we age our pot still and grain still spirit in two types of barrels: American oak bourbon whiskey barrels and Oloroso sherry casks. These are “seasoned barrels” because they’ve already been used to age a spirit. Irish whiskey is aged for a minimum of three years. Jameson Original sits in oak barrels for four years or more.
As the liquid rests, it soaks up the wood’s flavors. Our maturation warehouses aren’t climate-controlled, so as we cycle through the seasons, the barrels slowly expand and contract, further developing the flavor.
When it’s time to bottle, our expert blenders combine different barrels to ensure Jameson’s final flavor is consistent with the high quality standards we’ve had since 1780.

The Barrel Aging Process from Beginning to End
Here’s an overview of our whiskey-making process and how barrel aging fits into the overall journey.
Malting: Barley is delivered to the distillery. Some is malted while some is left unmalted.
Mashing and fermentation: The barley and malt are milled, combined with water, filtered, and fermented. The maize goes through a similar process, although corn isn’t malted. Akin to a strong flat beer, what results from the process of fermentation is called “wash.”
Distillation: The wash is collected and distilled in either pot or column stills. Distilling uses heat to separate the alcohol and flavors from the wash.
More distillation: Once we’ve distilled the liquid three times, we’re left with a grain spirit that hovers well above 90% abv (180 proof) or with a pot still spirit that sits well above 80% abv (160 proof).
Maturation: Here’s where barrel aging comes in. Oak Barrels are selected from our store and filled with spirit. The barrels are marked, catalogued, and placed in one of our maturation warehouses. The whiskey spends at least four years soaking up flavor.
Bottling: Our blenders can now start sampling the whiskey. Does it need more time? Is it ready to become part of a blend? If it’s ready, it’s blended and bottled.
How Long Does Whiskey Age?
The length of time required for aging whiskey varies depending on place or type of whiskey.
In Ireland, Scotland, Japan, and Canada, whiskey must be aged in oak barrels for a minimum of three years. At Jameson, most of our whiskey is aged for four years or more.
American bourbon is aged for either two or four years depending on the type of bourbon. Tennessee Whiskey has no requirement.
These are just the major whiskey producers. Germany, Australia, Taiwan and even Finland produce whiskey on smaller scales and have their own regulations around aging.

How Barrel Aging Impacts Whiskey’s Flavor
Barrel aging has a dramatic impact on a whiskey’s taste. Aging involves exposing the distilled spirit to the surface area of a wooden barrel over a long period, slowly developing the flavor.
Between 60%-80% of a whiskey’s flavor profile comes from barrel aging. Wood sugars, tannins, and lactones seep in, adding complex flavors and colors to the spirit. The charred layer on the inside of barrels helps to remove undesirable sulfur notes, which can be present in newly distilled spirits. The char level strongly impacts the sweet, smoky flavors you find in a good whiskey (we’re looking at you, Black Barrel).
Aging whiskey in seasoned barrels (barrels that have been used before) means the whiskey can absorb flavor from the liquid the barrel held before.
How Big Is a Whiskey Barrel?
Many different-sized barrels are used to mature whiskey. The standard bourbon barrels Jameson and American bourbon makers use hold around 200 liters (53 gallons). The seasoned Oloroso sherry casks Jameson also uses are much larger, holding 500 liters (132 gallons).
Bourbon barrels are around 36 inches or 91centimeters tall and sherry casks are usually 51 inches or 130 centimeters tall.
What Are Whiskey Barrels Made of?
Whiskey barrels are made with wood, metal and a lot of skill. Barrel makers, known as coopers, shape and ply wooden sections into staves which, when aligned correctly, will form a watertight container. Secured with metal rings and sealed, your barrel is complete.
The wood used for a whiskey barrel depends on the process, but the majority of barrels use European and American oak for its strength and malleability—it’s both breathable and relatively non-porous, durable, and full of flavor. The most common whiskey barrels are former bourbon barrels. This is because bourbon barrels can only be used to age bourbon once.
There are also barrels made of chestnut, acacia and other woods.

What’s the Best Barrel for Whiskey Aging?
Honestly, at Jameson we think we’ve nailed it with our seasoned bourbon barrels and Oloroso sherry casks. The seasoning, size, and materials make these oak barrels second to none when it comes to flavor. If you’re thinking of aging some of your own whiskey, then we can’t recommend our method enough!