A friend recently asked me for a recommendation for a decent quality Islay whisky. Hitting an online site to see what’s available locally, I came up with Laphroaig 10, Bowmore 12, and Ardbeg 10–all good candidates and priced within a few dollars of each other. Sending him the list, I braced for the inevitable question: “All things being equal, why wouldn’t I get the twelve year? It’s better than a ten year, right?”

While it’s true that the time a spirit spends aging has a huge impact on the resulting flavor, an attempt to reduce the complicated factors and interactions that go on inside a barrel to a single number is a hopeless oversimplification that confuses consumers. Spirit production and the resulting flavor is complicated and messy, and not readily quantifiable in every dimension. Sure, you can compare the alcohol by volume (ABV) content across two whiskies, but ten years of aging from Producer X may be vastly different than ten years of aging done by Producer Y. Unfortunately, this fixation on aging as reduced to digits leads some producers to play a numbers game, putting big numbers on their label to draw the eye of an unsuspecting consumer.

When all is said and done, a truthful age statement on a label can be useful, but only in the right circumstances and with an understanding of how aging spirits works. I’ll come back to that later, but let’s first wonk out about aging.

Barrel Aging Basics

As a distillate comes off the still, it’s a veritable soup of flavor compounds or precursors to flavors. The majority of this fresh distillate is tasteless – ethanol and water have no taste. Any flavor in a spirit comes from organic compounds collectively known as congeners. Breaking that term down (as I did in this article), the congeners of most interest are esters and aldehydes. There are hundreds of different esters and aldehydes, each contributing some particular aroma and taste, such as pineapple, vanilla, cinnamon, smoke, and eucalyptus. Although there are typically hundreds of congeners in a distilled spirit, they make up a tiny fraction of the overall liquid.

The primary task of barrel aging is not to make the spirit taste more “woody,” as some people believe. Nor is it to make a spirit “smooth.” We can’t really quantify what “smooth” means to the average drinker, and as we’ve learned (especially in the rum world), high sugar content is often perceived of as “smooth.” However, what a typical drinker does know is that a spirit that spends time in a barrel has a more pleasing taste than the unaged version. Why is that?

While a spirit ages in the barrel, a full-scale symphony of organic processes is underway. Water and ethanol are slowly evaporating through the barrel’s semi-porous wooden walls. The lignin in the wood breaks down in the ethanol to form compounds like vanillin, which taste of vanilla. Small amounts of sugars in the wood leach into the spirit. The simpler esters with fruity aromas transform into more complicated esters with honey and spice notes. And these are just the organic processes we know about–there is much more going on during aging that we still don’t fully comprehend.

No matter how carefully the distiller controls the distillation process to create a consistent new-make distillate, the moment it hits the barrel, Mother Nature takes over–and she’s anything but consistent and predictable. No two trees are identical, and hence, no two barrels are exactly the same. In fact, even two barrels made from different parts of the same tree will exhibit different aging characteristics, as the Buffalo Trace Single Oak Project demonstrated.

But wait, there’s more! Prior to use, all barrels are toasted or charred. Even with computer controlled processes, you’d be hard pressed to find two barrels that experience the exact same effect from a similar heat treatment.

Once filled with spirit and set aside to age, even the location of the barrel in the aging space makes a difference. Kentucky bourbon typically ages in structures called rickhouses, which rise up to six stories in height. It’s long been known that bourbon ages differently in the cooler, bottom floors of a rickhouse than at the top, where the heat rises and resides, especially during summer months. Maker’s Mark makes a point to rotate their barrels through different warehouse locations in an attempt to minimize variations.

In France, Cognac Ferrand (and Plantation Rum) CEO Alexandre Gabriel regularly samples thousands of barrels and moves them between warehouses, some of which are relatively dry while others are quite damp. As Alexandre is fond of explaining, alcohol and water in a barrel evaporate at roughly the same rate. Depending on the humidity of the aging warehouse, water may evaporate faster or slower than the ethanol, giving rise to the interesting phenomena of a spirit’s alcohol by volume actually going up in the barrel. Lower humidity makes the water portion evaporate faster, while higher humidity makes the alcohol dissipate more quickly.

Angel’s Share

Within the spirits world, the evaporation of the barrel’s contents is colloquially known as the “angel’s share.” While steady evaporation from a barrel is easy to grasp, it’s not quite that simple. The angel’s share is anything but consistent during a spirit’s life in a barrel. It begins fairly rapidly – sometimes as much as seven percent or more the first year. During subsequent years the angel’s share percentage drops–in the second year it may be only five percent. However, that’s five percent of the 93 percent remaining in the barrel after the first year’s losses. Over decades, the angels will take the vast majority of a barrel’s contents.

Each additional year of aging means less product to be bottled. Despite a distillery’s hard work and money literally vanishing into thin air, the angel’s share is responsible for a large part of the final flavor profile. Quoting Gabriel again, “During distillation, we keep what evaporates. During aging, we keep what doesn’t evaporate.”

Angels, flighty as they are, take their share in a very inconsistent way. This particularly influences the value implied by an age statement: The hotter the environment, the greater the angel’s share. Thus, if you took two reasonably similar barrels filled with the same spirit, and placed one on a Caribbean island near the equator, and the other in a much cooler environment, say… northern Scotland (not exactly known for its beach parties), you’ll get two very different angel’s share rates. The Caribbean barrel will evaporate faster and undergo the “aging” transformations more quickly than its UK.-relegated twin.

The above scenario isn’t contrived. In fact, it’s a very real-world example. When Jamaica’s Appleton ages a rum for 21 years, it’s in the scorching hot Jamaican countryside. But a U.K.-based independent bottler like Duncan Taylor might purchase new or lightly aged Jamaican rum and transport it to Scotland, where it continues to age for a decade or longer before bottling. In the cool climate of northern Europe, what goes on during aging can be very different than in the Caribbean. Remember when I said that aging is a symphony of different organic transformations? When you drastically change the environmental conditions (heat, temperature swing frequency, humidity), some “musicians” speed up, some slow down, some get louder, others softer.

Different spirit categories are usually aged in wildly different climates–rum in the intense heat of the Caribbean, bourbon in the hills of Kentucky with wide daily and seasonal temperature swings, and some single malt Scotch whiskies on a chilly cliff near the ocean in the far north of Scotland. Because of these vastly different aging conditions and angel’s share losses, comparing a twelve-year aged whisky to a twelve-year aged rum isn’t an apples-to-apples comparison. In practice, the relative transformation of a twelve-year aged Scotch whisky may take only seven years for a Caribbean rum. That’s why when hardcore rummies hear an age number, they reflexively ask, “Tropical or European aging?”

If all the above has made you concerned that age statements in isolation aren’t a great indicator of value, just wait – that’s only the first part of the story.

Barrel Reuse

American Bourbon holds a very special place in the spirits world. By law, anything labeled “bourbon” must be aged in new oak barrels. That is, after the barrel’s constructed, American-made whisky is the first and only thing that can go in the barrel. Afterward, that barrel is washed up. Done. No longer of use to the bourbon industry. Sure, a distiller could use a barrel for a second, third, or fourth time to age whiskey, but they couldn’t sell the resulting spirit as “bourbon”.

Luckily, the makers of other spirts like Scotch whisky, rum, and tequila labor under no such restrictions. They buy previously used bourbon barrels and age their product in those barrels many times over. Equally fortunate to those producers, the American bourbon industry makes, uses, and sells a LOT of barrels that that end up in aging warehouses all over the world.

It’s not just frugality that drives the market in bourbon barrels. Every moment that a barrel holds a spirit, the wood itself is transforming. Small amounts of sugars leach into the spirit. The lignins in the wood that create vanilla flavors dissipate. The reason bourbons are so vanilla forward is because they get first crack at the freshly charred wood. A Scotch whisky that goes into it a second, third, or fourth time gets very different barrel conditions.

Each successive aging cycle causes the wood to become less and less effective at some aspects of aging. In fact, after enough time, barrels are considered “neutral” – they don’t add any measurable wood-derived flavors. These barrels (or the wood from them) are sometimes used as “marrying” barrels, for integrating two or more spirits into a final form prior to bottling. (Glenfiddich in Scotland is one such distillery that does this.) Or an exhausted barrel may simply be sold for scrap and wind up as somebody’s planter.

This isn’t to imply that previously used barrels can’t be ideal for aging spirits. They just provide relatively fewer extractive-based flavors (like vanillin in first-use bourbon casks), and relatively more oxidation-related transformation. In fact, a sufficiently aged and seasoned barrel can impart rancio flavors, which are highly desired in cognacs. Cellar masters who’ve mastered the art of aging look for well-seasoned barrels as they provides more overall control as the spirits evolves. They may even age a batch of spirit in both newer and older barrels for varying lengths of time.

It is possible to recondition barrels–scrape off a layer or two from the inside, and then re-char the barrel. (Peru’s Cartavio distillery uses this practice.) But while this treatment may provide a few more uses, the aging induced by reconditioned barrels is still not exactly the same as a new barrel.

Given that barrels can be and almost certainly are reused (except in the case of bourbon), the problem with an age statement is vividly clear: You have no idea how many times a barrel has been reused. Was it a fresh, relatively new barrel with only five years spent aging bourbon? Or was it on the fifth fill, having spent thirty years aging bourbon and who knows what else? There’s nothing inherently wrong with aging in previously used casks, and in many cases, they may be preferable. But unless the producer specifies exactly what sort of casks and for how long the spirit spent in each, a single number can’t begin to convey the aging environment.

As you might expect, respectable producers have taste and quality standards. It’s in their best interest to maintain a flavor profile, so they don’t just grab the nearest empty barrel and fill it up. Instead, they employ experts whose primary responsibility is to track the life-cycle of every barrel and ensure a steady supply of usable barrels.

Barrel Size

With the recent surge in small, “craft” distilleries rushing to make the next great American Bourbon, some distillers goose the aging process by using smaller barrels. By law, to be called “straight bourbon” the spirit must be aged in new charred oak containers for a minimum of two years. Now, there’s a reason the big players like Jim Beam and Buffalo Trace aren’t selling their mainstream bourbons with only two years of aging–they need more than two years in the barrel to mature properly. But to a small distiller, every year in the barrel means less product to sell (due to the angel’s share) and less money flowing into the coffers.

While the big players have standardized on 53 gallon barrels for the most part, some upstarts age in substantially smaller barrels–say, fifteen gallons. The geometry of a smaller barrel means more wood is in contact with the spirit contents, relative to a larger 53 gallon barrel. With more wood in contact with liquid, some aspects of the aging process are naturally accelerated–but other aspects aren’t accelerated in the same way. Many experts think that a spirit aged in a smaller barrel just doesn’t achieve the same wonderful flavor profile as a larger barrel given more time.

So, when you pick up that bottle of three-year aged bourbon from that new, hip, supercool distillery, ask about what type of barrels they used, because three years in a fifteen gallon barrel isn’t the same as three years in a 53 gallon barrel. The use of smaller barrels isn’t necessarily a bad thing, but be aware of what that means when it comes to age statements.

Deceptions and Lies

By this point, it should be pretty clear that age is just a number and not a particularly good indicator of how well a product was aged. In the best circumstances, local laws or producer integrity compels the number on the label to be the minimum duration that every drop in the bottle spent in a barrel. But that’s all you really know, e.g. a twelve-year single-malt scotch whisky spent at least twelve years aging in oak, in Scotland.

Scotch whisky, Cognac, Bourbon, and rums from countries like Jamaica and Barbados require that an age statement, if present, indicates the youngest age of anything in the bottle. However, that’s not a requirement around the globe.

Some countries like the U.S. have laws that seem clear about age statements and numbers on a label, but in reality aren’t uniformly enforced. For the record, the TTB, which regulates spirits in the U.S. says the following about age statements:

the statement of age (whether required or optional) must appear as: ‰“____ YEARS OLD” (Fill in blank with specific age or age of youngest distilled spirits in blend) OR “AGED ____ YEARS” (Fill in blank with specific age or age of youngest distilled spirits in blend)

In the rum world, the solera aging technique creates some amazing rums. But because barrel contents with older spirits are periodically blended with liquid from a younger barrel, it’s hard to assign an age to the resulting spirit. A few drops in the final product may have sped through all the solera levels in a few years, while other drops lingered around for decades. So what age do you label the product with? An average age? Sure, you could do that, but the typical average age of a solera aged rum isn’t a big number like twelve or twenty-one that impresses buyers.

Ron Zacapa is the most well-known rum with a misleading age statement. The bedrock of the line is Zacapa 23. The typical consumer sees the “23” on the label and likely thinks it must mean 23 years of aging. Heck, even the folks selling Zacapa seem confused and label it as a “23 year old” rum. In fairness to Zacapa, if you look beyond the front label, the brand is (presumably) honest about it being a solera blend of rums between six and twenty-three years. Still, the big “23” on the front label will likely confuse a non-wonky rum consumer.

A more egregious example is Zaya rum. Once made in Guatemala at the same facility as Zacapa, its production got moved to Trinidad. At one point, the top of the Zaya bottle had a prominent, round sticker surrounded by raised glass, proudly proclaiming twelve years of aging. Recently, the Zaya brand changed hands, and while the look and feel of the bottle remains the same, if you look closely at the “12” sticker, it doesn’t say “years” anywhere. Instead the brand now states the rum is a blend of 12 rums. Deceive your customer much, Zaya?

And finally there are producers who stick a number on their label without any statement at all about what it means. In the bourbon space, Buffalo Trace’s Old Charter used to be an eight-year bourbon. That age statement has been dropped, yet the label still has a prominent “8” above the name. When it comes to rum, Flor de Caña dropped the age claim from their rums, yet their popular rums like the Centenario 7, 12, and 18 still feature those numbers prominently.

In short, numbers you find on spirits labels are completely a “buyer beware” situation.

What Good Are Age Statements?

Having worked hard to beat down the idea that fifteen years in a barrel is always better than twelve, let’s take a step back and consider where a truthful age statement can be helpful.

When it comes to Bourbon, and when talking about the major Kentucky (and nearby) producers, the effect of ten years of claimed aging should be roughly equal from producer to producer. They’re all aged in a similar climate, and they all started with new charred oak barrels, so reuse isn’t a factor. Of course I’m not saying the bourbons will taste the same, just that they had a fairly level playing field when it comes to aging. Purists may point out things that make a difference, like what level of the warehouse a barrel resided in, but the overall point stands.

Another scenario where age statements typically contribute value is within the same brand or producer lineup. For instance, Glenfiddich features a core product series that includes age statements of 12, 14, 15, 18, 21, and 26 years. The odds are likely that each of these products was aged in the same warehouses, with similar barrels, and with the same team managing the barrels in terms of re-use. In the absence of contrary evidence, it’s reasonable to assume that the fifteen year bottling had very similar aging conditions to the twelve year, just three years longer. There are obviously many exceptions to this, and you need to read labels carefully to evaluate each situation on its own merit.

When they’re truthful, and from a reputable producer, age statements are useful for conveying value. After all, each year a spirit ages in a barrel means there’s less to bottle. That’s why the price of a fifteen year whisky is often substantially more than 25 percent higher than its twelve year sibling.

It’s easy to be mislead by nebulously defined, often-unregulated terms like XO, VSOP, and Anejo. Similarly, the rise of non-age-statement (NAS) spirits is a way for producers to work with a wider range of component spirits without being bound by the rigorous “minimum age” requirements of a stated age. However, as Foursquare Rum master distiller Richard Seale says “When a premium price is demanded, the age statement is non negotiable.”

At the end of the day, age statements are just one tool in evaluating a product, and not a particularly precise one at that. It’s easy to reflexively reach for whatever the biggest number is, but bigger isn’t always better. A five year rum aged in new charred American oak may taste far better than the same spirit aged 15 years in a practically neutral cask. What the above insights about environmental conditions, cask reuse, barrel size and age statement deceptions, you now have the tools to apply a much more critical eye the next time you pick up a bottle.