Even beyond its intoxicating properties, alcohol is a key component in all distilled spirits. “Alcohol provides structure and texture, and drives flavor — just like acidity in wine,” explains Maggie Campbell, president and head distiller of Massachusetts’ Privateer Rum. The key to crafting a high-quality spirit, Campbell says, is finding the balance between alcohol content and flavor profile.

Spirits aficionados with a keen eye for detail may have noticed that this balance seems to be found at 40 percent alcohol by volume (ABV), or 80 proof. Many popular spirits, including vodka, tequila, and white rum are almost exclusively bottled at this strength. But examine the labels of aged liquors, such as whiskey, and it’s soon clear that this is not always the case. For these spirits, alcohol strengths vary wildly from 80 proof all the way up to 120 proof and beyond.

Such disparity raises an intriguing question: Why are so many spirits bottled at precisely 80 proof? And while this appears to be the sweet spot for some types of liquor, why does proof then vary so widely in others?

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The History and Economics of 80-Proof Liquor

One of the main reasons so many spirits are 80 proof is somewhat simple: It’s the minimum level allowed by law in the U.S. A seemingly arbitrary number, the 80-proof minimum actually holds historic significance, according to drinks historian David Wondrich.

There are two ways of measuring the strength of spirits, he explains: alcohol by volume [proof] and alcohol by weight. Historically, the English used alcohol by weight. “The minimum proof they would tolerate was around 30 degrees under proof by weight, which is 39.9 percent ABV,” says Wondrich, adding, “Beyond that, things begin to get a bit watery.” Conveniently rounded up to 40 percent ABV, the benchmark most likely guided American legislators when they passed the Federal Alcohol Administration Act in 1936.

While distillers are free to produce spirits above this proof, there are economic advantages for sticking to the baseline. “The principle is simple: The higher the proof, the higher the tax,” says Allen Katz, co-founder of Brooklyn-based New York Distilling Company (NYDC).

Katz chooses not to be guided by this principle at NYDC. The distillery’s portfolio even includes a precisely potent 57 percent ABV Navy-strength gin. However, he says, it does make sense for scale brands that rely on selling high volumes at competitive prices to stick to the lower, less expensive 80 proof.

In the case of aged spirits, which take years to mature and have the additional cost of oak barrels in their production, diluting to this strength also allows producers to stretch out their stocks. The combination of lower taxes and larger volumes of product is surely an attractive proposition for any business. But this in turn raises a different question: Why is it so common to find aged spirits bottled as high as 63 percent ABV?

The Science of Bottling at 80 Proof (and Above)

The aromas and flavors found in alcoholic spirits come from volatile flavor compounds. Unlike a glass of wine, which requires swirling to coax out those notes, the volatile compounds in spirits evaporate naturally. The more a spirit is diluted, the quicker those compounds evaporate, meaning a lower concentration of aromas. This may be desirable for spirits like vodka, but a product with a weak profile is unlikely to make waves in the whiskey world.

For aged spirits producers, therefore, the crucial task is to find balance between proof and profit margins. Then, there are consumer preferences to consider: “If you want a bolder, more complex flavor, you start racking up the percentage (or diluting less),” says Oregon-based spirits educator Hoke Harden. For the full experience, this means bottling at cask strength. But high-proof bottlings can be off-putting for consumers, so whiskey distillers typically dilute their flagship offerings to somewhere between 86 and 100 proof, Harden says.

Privateer Rum’s Campbell also takes consumer preferences into account for her distillery’s New England White Rum — the only spirit it bottles at 80 proof. “We found that in our community, a lot of people are buying spirits for casual, approachable drinking at home,” she says. “Eighty proof is something they have told us they really like.” Campbell adds it’s still possible to produce a spirit that is aromatic, textured, and deeply flavored at this strength by using high-quality base material (in this case, molasses).

Similarly, tequila is made with mature agave plants, or piñas. The process includes multiple steps, during which the piña is cooked, crushed, fermented, distilled, and aged. Each step contributes complexity. “You can get nuance and still maintain a baseline of 40 percent ABV,” says NYDC’s Katz. (In Mexico, tequila is typically sold and bottled at less than 80 proof.)

In vodka, there are further scientific reasons for sticking to the 80-proof level or thereabouts. When you drink a high-ABV spirit, the alcohol combines with specific receptors throughout the body and sends a pain message (think: heat) to the brain, says Gwen Conley, director of quality and innovation at San Diego’s Cutwater Spirits. When the spirit is diluted, or includes high concentrations of flavor compounds from processes like barrel aging, the receptors bind to those instead. “Vodka doesn’t have those compounds, so you’re just getting the burn,” Conley says.

Why Whiskey Proof Has Changed Over Time

Nowadays, it’s common to find American whiskeys that clock in at the minimum 80 proof, a practice that’s been allowed since at least the 1930s. But it wasn’t until the 1950s that swathes of producers started dipping below 100 proof; and even then, it wasn’t completely out of choice. “It really was fueled by consumer trends,” says Bradford Lawrence, rye whiskey specialist for Beam Suntory.

By the 1950s, American whiskey drinkers had developed a taste for lighter-profile Canadian whiskeys (borne out of Prohibition) and lower-proof blended Scotch. U.S. distillers saw those trends and soon followed suit, first diluting to 86 proof, Lawrence says. Then, in the 1980s, came the growing popularity of 80-proof clear spirits and newly introduced light beer. By this point, whiskey sales had hit a record low. Those who were drinking whiskey were mainly enjoying it in highballs with soft drinks. “If [a distillery] slipped an extra six points down to 80 proof, no one was really going to notice,” Lawrence says.

Beam Suntory-owned Old Overholt was among the many brands that adapted over time to consumer preferences, finally hitting 80 proof in the early 1990s. But now, along with many other whiskey brands, Old Overholt is once again ramping up its ABV. This time around, the change appeases trade as well as consumers. “There’s a tremendous amount of love for the Overholt brand amongst bartenders,” Lawrence says. “We found that adding an extra six proof points helped [the whiskey’s] rye notes shine. More importantly, the higher proof helps with cocktail creation.”

Crafting Higher-Proof Spirits for Cocktails

The growing trend for higher-proof bottlings is not confined to whiskey, nor is it only occurring within styles that have traditionally been enjoyed above 80 proof.

When California-based Altamar Brands started developing its Elvelo tequila in 2015, director of education Brandon Cummins worked alongside second-generation master distiller Carlos Hernandez Ramos and his son, Charlie Hernandez Ramos. A former bartender, Cummins wanted a profile that would stand up to bold cocktail ingredients. So the team sampled 13 different proof points, ranging from 80 up to 110. “We were somewhat arbitrary in our selection but we knew there was going to be a sweet spot, likely somewhere in the middle,” Cummins says. After a series of blind tastings, they whittled the selection down to three proofs. To settle on a favorite, they tasted each example mixed in five different cocktails. “On all five cocktails, the consistent, unanimous winner was 44.5 percent ABV,” Cummins says.

Spirits entrepreneur David Kanbar went through a similar process prior to launching King St. Vodka with Kate Hudson in 2019. “It was a matter of experimentation,” Kanbar says. “We found that when we turned up the alcohol a little bit — in this case to 43 percent — not only did it bring out a little bit more flavor, it gave the vodka more character.”

Swedish-based Absolut also offers a higher-ABV vodka called Elyx, which it bottles at 42.3 percent ABV. This very specific proof was chosen because the brand felt that it was the ideal for enjoying neat, on the rocks, or in cocktails.

Even as many modern bartenders are turning to higher-proof spirits, it’s not time to write off 80-proof spirits just yet. It all depends on how you’re enjoying the spirit. “There’s a kind of modern bartender prejudice against 40 percent ABV, and I will admit to a sharing that when I’m mixing drinks,” says historian Wondrich. “But if you’re dealing with a good quality tequila, 40 percent is fine — certainly for sipping.”