Everything You Need to Know About High Altitude Whiskey-Making

Stranahan's Rob Dietrich
Stranahan's Rob Dietrich.
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As the thirst for American whiskey continues to grow, so too does its diversity of provenance. Not long ago a connoisseur might shun bourbons and ryes born beyond the state lines of Kentucky, Tennessee, or Indiana. Today, such prejudices would be quite unwise. Look at the lush liquid rolling off Rocky Mountain stills, for example: Colorado alone is now home to more than 80 distilleries.

For the craftsmen and women pioneering these products, gaining recognition is but a minor hiccup compared to the more daunting challenges of physics. Making whiskey high in the hills, you see, doesn’t work quite the same way as it does at sea level.

“When you’re this high, the boiling point differs,” explains Michael Myers, master distiller at Distillery 291 in Colorado Springs. “At 6,035 feet, water boils at 200 degrees instead of 212 degrees. When you mash in you bring your mash to a boil, so I had to adjust from the typical methods. The whiskey when it is coming off the still also comes off at a lower temperature.”

The higher the elevation, the thinner the atmosphere. That means lower pressure, which affects the way water behaves. Anyone who’s tried making mac n’ cheese at a ski resort can relate.

So for distillers migrating from the Bluegrass State, where the average elevation is closer to 500 feet, a slight learning curve awaits. Namely, they’ll have to tweak where and when to make their cuts. But the basic process remains true enough.

“The primary purpose of distilling is to concentrate unwanted congeners developed during fermentation so that they can be removed—heads and tails cuts—and to rectify the proof of the alcohol,” says master distiller Greg Mezte of Old Elk Distillery in Fort Collins. “The only difference between high altitude and low altitude distilling is the temperature that you distill at to achieve the same result. For instance, you may distill at 192-degrees Fahrenheit at low elevation to achieve a 135 proof distillate where it may be 185-degrees Fahrenheit to achieve the same proof at 5,000 ft. elevation.”

These precise adjustments can be calculated with great accuracy. Thanks, math. Where things get less predictable, however, is during maturation. According to Mezte, “the ‘angels’ share’ losses can be expected to be higher due to the lower vapor pressure and lower humidity associated with higher elevations. This allows the distillate to escape the barrel easier.”

It doesn’t always work that way, though. Which is why Stranahan’s Colorado Whiskey relies on climate-controlled warehouses to insure consistency at its Denver home base. “We keep our barrelhouses at 70 degrees in temperature, 45 percent humidity, year round,” says master distiller ‘Whiskey Rob’ Dietrich. “The barometric pressure that comes off the Rocky Mountains is our friend. It creates positive pressure inside the barrel. With warm temperature, we keep the pores of the wood open.” A boisterous conversation between oak and whiskey results.

And for those that avoid tinkering with warehouse climate, it’s not all bad either. A drier atmosphere means water evaporates out of the oak before the alcohol. So while overall volume is lost, barrel proof actually goes up as it ages in the warehouse. “I also think the higher altitude causes the whiskey to be a little drier in flavor versus a Kentucky bourbon which may be more sweeter,” says Myers. “Colorado is consistently cleaning up in the rye category. It may be because the traditional notes of rye are spicy, and maturing at this altitude tends to lend itself well to that flavor.”

But to suss out that flavor he’s constantly mindful of how elevation impacts the stave. “The barrel manufacturer recommends putting water inside the barrel to prep it,” notes Myers. “We actually hydrate the exterior of the barrel. We never have to worry about wood rotting at this elevation.”

You do have to worry about the weather, however. “When there’s a storm rolling in off the Rockies, it affects our still run times,” observes Dietrich. “The shifting barometric pressure changes the oxygen. When making the cuts, this might mean an extra 45 minutes or an extra 2 hours depending on the shifts.” Distilling at night, Dietrich could reliably predict if a weather system was coming in based upon these irregularities. “I sort of became an amateur meteorologist,” he muses. Thanks to the runaway success of high mountain whiskey, though, he won’t have to quit his day job anytime soon.