There are parallels to be drawn between all creative processes, including distilling. For example, when it comes to whiskey, selecting the grain, yeast, and fermentation strategy is like pulling together the loose words and notes that make up the first draft of a song. Distilling a white dog is the first take, its character shaped by still, temperature, time, and cut. Then it goes into a barrel to produce the final edit, rendered by barrel type, climate, and the length of time the spirit matured, infusing with the character of that barrel.

However, there are other tools at our disposal. Entry proof, to steal an idea from ADI’s own Eric Zandona, is the mixing desk in which flavor notes are faded in or out to make those final tweaks to a chart-topping track, one that resonates in the senses and the souls of its listeners as much as a good whiskey resonates in the senses and souls of its sippers.

That said, entry proof seems to be a somewhat elusive topic. There are some threads of discussion online, along with articles and a hotchpotch of scientific research. There is a growing interest in utilizing a lower barrel entry proof in the craft movement, which many practitioners say harkens back to pre-Prohibition days.

A Brief History of Barrel Entry Proof

Prior to Prohibition, entry proof was generally quite low, around 107 proof. Way back in the 1830s, brands like James Crow were sold by the barrel to establishments that would sell directly from the barrel into the customer’s glass. The drink had to be palatable straight from the barrel — and a lower barrel entry proof meant that it was.

However, after Prohibition ended, new regulations were introduced. Between April 3, 1958, and July 1, 1960, distillers were allowed to experiment with proofs between 110 and 160. In 1962, entry proof was set at a maximum of 125.

This change in regulation led to the creation of the concept of “barrel proof strength” and fed into the idea of watering down the barrelled spirit, bottling it, and then selling the bottle. This made each batch more productive, reducing the number of barrels needed for aging and lightening the flavor of the end product.

It was all about cost efficiency. One of many routes into more efficient production was the development of high-yield wheat at the cost of flavor, as discussed in my previous article for Distiller. Another was barrels. Filling barrels at a high entry proof, then watering down after you remove the whiskey from the barrel, will produce more volume of whiskey per barrel than barreling at a lower entry proof, which saves on barrel cost.

Coppersea barrels at 105 and lists low proof barrelling on their website as a heritage method.

A Modern Return to Lower Entry Proof?

There has, however, been a pushback to increased barrel entry proof from the craft distilling movement. Many distillers are now prioritising quality and flavor over output. Making less product of a higher quality is the name of the game, and one of the methods being implemented is using low entry proof.

I first learned about the practice from Coppersea Distillery in New Paltz, New York. Coppersea barrels at 105 and lists low proof barrelling on their website as a heritage method. They maintain it creates a more balanced extraction between the fruity notes extracted by water and the vanilla and caramel notes extracted by alcohol. (Yes, water and alcohol pull separate compounds out of wood.)

In addition to this, the lower the proof, the faster the spirit ages. Sugar dissolves more easily in water than ethanol, so a lower proof means wood sugars are absorbed more quickly into solution. Water also effectively dissolves phenolic compounds from wood, which give an astringency, dryness, and bitterness to the character of the spirit. We do want some phenols in our whiskey, as they add character and can bolster the esters. However, we don’t want too many phenols. Oxidation transforms some phenols to quinones, which are less acidic, astringent, dry, and bitter.

According to Zandona, there is a stark difference in flavor between whiskeys aged at low and high barrel entry proofs. He uses the examples of Maker’s Mark, which is barrelled at 110 proof, and Larceny, which is barrelled at 125 proof. While not exactly the same, their variables are otherwise relatively similar. Tasting them side by side, it’s obvious that Maker’s Mark has a softer, rounded quality as compared with Larceny, which is a great spirit but is loud and peppery in comparison. Zandona has made a personal observation that a wheated bourbon shows “more of the other production choices, such as yeast character and barrel entry proof.”

Barrel Age Matters, Too

If these ideas are selling you on experimenting with low entry proof, keep reading, because the plot thickens. Depending on your barrels, it may not give you the results you’re looking for. I caught up with consultant and all-around barrel expert Julia Nourney to find out a little more about the technicalities in Nourney’s area of expertise, which focuses on products like brandy and malt whiskey that age in used casks.

On a new barrel, Nourney’s advice is to start low. Treat that first aging as laying a base coat. “If you take a new cask into the family, you don’t want to be forceful with it. You start low and the longer you use it, the higher your entry proof will go,” she advises. Speaking with French Limousin oak in mind, she explains that “the wood is full of tannins, spicy. In Europe, most people tend to look at what the Scottish industry does. And if you enter the spirit at the European standard of 127, the alcohol just sucks everything out of the cask immediately, and after one week you have a lot of color, a lot of taste, and almost no oxidation. If you leave the spirit in there for three years, you end up with wooden soup.”

When using a barrel that has a history, whatever it is, Julia’s advice is to fill at a slightly higher proof than what had been in there before. Why? If you fill at a very high proof, you pull so much flavor in the first round that you’re not left with much else for future uses. If you go in low, you’re going to get more uses out of it.

Nourney suggests around 106 proof, and monitoring the cask carefully during its first use to avoid over-extraction. After that, the barrel will be exhausted to 106 proof, so, for the second use, she advises filling at 108 proof, with the understanding that the barrel will take a little longer to work its magic – two months, maybe six. With each successive use, the entry proof should be slightly higher to get the most out of the barrel. American oak is a similar process, as is wine-filled American oak.

“Nowadays,” Nourney explains, “when resources are rare, you want to keep the cask for as long as possible.” Naturally, if the cask has already been exhausted by a previous fill at 126 proof, she would recommend going in slightly higher.

Interestingly, that European standard of 127 proof seems to be due to how barrels are used in the United States. Ex-bourbon casks are often filled at the American limit of 125 proof, and many of these casks are then transported to Scotland for whisky production. It’s fascinating to think this has such a large impact on barrel aging in Europe. Distillers tend to follow the Scottish standard as a rule, and few experiment further. I can’t help but wonder what different results distilleries would get with a little experimentation and that they’re missing a trick by not thinking about this detail.

Michael D’Souza of Paul John Distillery in India gave me a little insight into barrel aging there. Indian regulations are the same as British in that anything above 114.2 proof is considered over proof, and anything below is under proof. Michael explained that according to his studies, “the optimal interaction and extraction happens below 130 proof. In order to get maximum results we fill our casks at 127 proof.”

Paul John Distillery in India, where Indian regulations are the same as British in that anything above 114.2 proof is considered over proof, and anything below is under proof.

When I first started researching barrel proof, I wondered if there would be a clear answer to which was “better.” It seemed that high entry proof saved cost, while low entry was a higher quality, and perhaps more expensive, option. But it’s just not that simple. Like a lot of things in distilling, there are many variables, and you need to experiment to work out what’s best for your spirit. This sometimes comes at a cost and time investment that distillers can’t justify. It’s tweaking a song that already sounds pretty good.

Many variables are routinely stated on the label: mash bill, barrel type, years aged. Yet I’ve hardly seen anyone stating low entry proof on their barrel or website. Why is this?

I think it comes down to the lack of consumer understanding on the difference entry proof makes. This could change with time, though. Consumers are becoming much more interested in what’s in the glass and how it was made. It’s like The Philosophy of Whisky author Billy Abbot said to me recently: “Cask finishing of whiskeys used to be something that you did as part of good warehouse management, whereas these days it’s a key selling point of many products.”

Who knows? Perhaps one day we’ll see this information on the bottle, much like a mixing artist is listed in the credits on a recording.

Previous articleHonolulu 10 Top Bars
Next articleLong Train Runnin’
In April 2015, Bernadette Pamplin began writing working in a gin bar. She fell deeply in love with gin, particularly its history and the stories associated with each bottle, as well as the incredible complexities of botanicals, distilling processes and serves. She previously worked as a Brand Ambassador in a large touring gin festival, and currently she runs her website Under the Ginfluence. She also writes for Gin Magazine,, Distiller Magazine, and works behind the scenes at the Craft Distilling Expo.