Old Elk Bourbon Embraces the Science of “Slow Cut” Water Proofing for Whiskey

Drink Features whiskey
Old Elk Bourbon Embraces the Science of “Slow Cut” Water Proofing for Whiskey

To an outsider who knows little of the spirits/distillery industry, one might expect a certain set of “best practices” to emerge that all professional distillers would follow. In this sort of oversimplification of the field, members of the industry would all agree that the data shows one method of distillation, proofing, aging, etc. to be “best,” and everyone would simply follow that example.

Of course, this isn’t how it actually goes, given that even master distillers with decades of experience often disagree on the best techniques to extract flavor, or have their own secret processes. Try telling one of those professionals, 30 years into their career at a major whiskey distillery, that some chemist believes he should be doing things a different way and see what his reaction is like. I can tell you with some certainty that it’s probably not going to be positive.

And of course, there are practical considerations as well. Are there certain processes that might result in a better-tasting spirit? Yes, but some of those processes take longer to implement—and for companies moving product on a massive scale, time is directly correlated to profitability. Each production choice that involves additional time therefore becomes a balancing act between “how much could this possibly improve the product?” and “how much is that potential improvement worth to us?”

With that said, it perhaps makes sense that some more time-intensive processes are first normalized by smaller independent distilleries, as higher priced products are already an expectation that micro-distillery patrons understand. As a result, these smaller distilleries often find themselves on the cutting edge of new, potentially valuable techniques—and one of those techniques is “slow” water proofing. This concept revolves entirely around the rate by which water is added to a barrel proof whiskey in order to dilute it to the level where it will eventually be bottled.

The concept of slowing down this process is not exactly new, but it’s used by a relatively small handful of distilleries. These distillers include such names as Kings County Distillery in Brooklyn, or Still Austin Whiskey Co. in Texas, but it’s Fort Collins’ Old Elk Bourbon that has really made this particular process one of their key selling points. They’ve even trademarked what they refer to as the Slow Cut™ proofing process.

But what is the supposed advantage of slower dilution? I was curious to find out, and I was able to obtain samples from Old Elk of the same blended bourbon, diluted both “fast” and “slow” in order to compare them against each other. The results were fairly striking.

The Theory of Slow-Cut Water Proofing


When we talk about “proofing,” what we’re referring to is the reduction of a whiskey’s alcohol concentration after it’s finished its time aging in the barrel. Bourbon can legally enter a newly charred barrel in the U.S. at up to 125 proof (though some distilleries increasingly use lower entry proofs), and the effects of evaporation mean that a whiskey entering the barrel at 125 proof can actually exit it in the low 100s or 140s and beyond—we wrote more about this phenomenon here. For a brand that is actually bottled and sold at say, 90 proof, however, that means water will then be added to the whiskey after the barrels are emptied, and before the bottles are filled. This is called “proofing.”

Most industrial distilleries simply do this process quickly—they add the amount of water necessary to bring the batch down to the desired proof, and then move on to the next step. Slow proofing, on the other hand, adds tiny amounts of water in stages—this process can last days or weeks, as the proof is gradually adjusted and the whiskey rests in a large holding tank of some kind. The proponents of this process point to two specific advantages it confers:

1. It reduces the risk of saponification

“Saponification” is the creation of chemical compounds when certain fats/oils come out of suspension in a water-whiskey solution, and specifically those that result in a flavor that is often described as “soapy.” If you’ve ever had a whiskey that reminded you unpleasantly of soap, this is likely the culprit. Saponification can happen in many whiskeys when proofed down significantly, but slowing the process makes saponification less likely to occur. This is just one reason why widely admired whiskey consultants/blenders such as Nancy Fraley have often recommended slow water proofing to their clients, or used it themselves. The process is also apparently common in the world of brandy blending.

2. It generates less heat, leaving delicate flavor compounds intact

Slow water proofing is perhaps less known as a process in American whiskey than in the worlds of brandy or rum because more American whiskey is derived from column stills (rather than pot stills), which distill the spirit to a higher initial proof and leave fewer congeners (that’s a chemical term you can think of as “flavor compounds”) in the solution. But still, there are congeners involved, and these are delicate flavor compounds that are surprisingly easy to destroy before the whiskey is bottled. And one of the things that destroys congeners? Heat.

You wouldn’t think that adding water, of all things, to a whiskey would result in the generation of heat, but that’s exactly what happens. The two liquids merging into one solution causes the release of energy—an exothermic reaction. Dumping a bunch of water into a big batch of whiskey, therefore, actually generates a lot of heat. And this heat can destroy congeners in the solution, driving away delicate flavors and leaving less desirable ones. Slow water proofing is intended to get around this because far less heat is generated each time a tiny amount of water is added. In other words, it’s a slower process, but it theoretically leaves more flavor intact.

Tasting: Old Elk Blended Straight Bourbon Whiskey (“Fast Cut” vs. “Slow Cut”)


The obvious thing to do at this point? Taste examples of the same whiskey with a fast cut vs. a slower cut. And thankfully, Old Elk was able to provide samples of exactly that—two slightly different versions of their flagship Blended Straight Bourbon Whiskey, one of which was proofed quickly and one of which was proofed with their Slow Cut™ proofing process. Each was otherwise identical: A rather unusual bourbon mashbill from MGP of Indiana, featuring a higher than normal proportion of malted barley along with corn and rye. I was also able to chat with Old Elk Head Distiller Kate Douglas as I tasted the samples, picking her brain about the process.

I’ll be honest: I was by no means convinced in advance that the difference between these two samples would be at all obvious. The rate of water proofing seemed to me like something that would probably make a very small overall difference in the aromas and flavors of two samples of the same whiskey, and I wondered if the differences would only be detectable by a professional distiller/blender rather than by the average consumer.

Turns out, I needn’t have worried, because the two samples proved to be surprisingly distinct from one another. Whereas the “fast cut” sample of Old Elk’s flagship product had more distinctly malty tones, with lots of oatmeal, doughy/biscuity characteristics, green apple and citrus, the Slow Cut™ sample took that profile and then layered additional notes on top of it. The ethanol was less pronounced on both the nose and the palate, allowing additional cocoa and red fruit notes to emerge. It simply ended up reading as kinder and gentler on the palate, which better fit the original intention of this particular product. It contained richer notes of caramelized sugar, cocoa and malted milk, and a more nuanced and gentle sweetness. I have no doubt that if these two samples were blind tasted by a large group of people, the majority would probably favor the Slow Cut™ sample. Tasting them side by side, the benefit of the process seems increasingly obvious.

And that’s ultimately one of the things I love about this field—there’s always more discoveries to be made. There are facets of the process you don’t think will have a great deal of impact on the outcome, and they can be far more important than you realize. As for Old Elk, they’ve discovered a particular process that seems to perfectly fit their identity, and it makes me wonder if we’ll see variations on this process being applied at more and more distilleries as time goes by.

Jim Vorel is a Paste staff writer and resident brown liquor geek. You can follow him on Twitter for more drink writing.

Share Tweet Submit Pin