The Right Attitude to Distilling at Altitude!

08 December 2022
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More consultant-baloney that needs to be addressed. I read an article that "researched" distilling at altitude. The consultant's conclusion was that craft distillers located at higher altitudes have the amazing benefit of "gentler boils". And the article implied that these craft distillers have a benefit to others, located closer to sea level, as these low-altitude distilleries are confronted with more aggressive boils in their stills.

Now, everyone is entitled to their own opinion. But no one is entitled to their own facts. The right attitude to distilling at altitude is not based on an opinion, but on science. Science perfectly explains how distilling at altitude differs from distilling at sea level. Spoiler alert: the consultant that claims high-altitude distilling is favored by a more gentle boil in his still is completely wrong. Science teaches us it is the exact opposite.

Air pressure

The earth is surrounded by a layer of air. This air asserts a pressure downward, on the earths crust. Or on the people, distilleries, and stills on that crust. A lower location results in a bigger layer of air above your distillery. A bigger layer of air above your "lowland" distillery results in high air pressure.

A distillery that's located at 2,000 meters or 6,000 feet could be called a "highland" distillery, or a "distillery at altitude". The layer of air above this location is smaller, resulting in lower air pressures at these higher altitude distilleries. Why is this important? Because air pressure is one-on-one related to boiling temperature.

Pure ethanol boils at 78.3 Celsius. At sea level, that is. In Utah and Colorado, visiting distilleries at altitudes of 2,000 meters and more, I have seen boiling points drop to as low as 72 degrees Celsius. How come that high-altitude distilleries are faced with lower boiling points of pure ethanol? Because there is less air pressure.

A boiling liquid uses all the energy input to form gasses. The bigger the air blanket, the higher the air pressure, the more back-pressure those gasses are met with. Higher pressure, including higher air pressure, results in higher boiling points of the liquid that generates the gasses. Contrary, at high altitude, in a low air pressure situation, gasses are not pushed back as hard. They find less resistance and the boil starts earlier because of it.

Gentle boil, really?

As air pressure creates "resistance" to the boil, it slows down both the boil and the vapor speeds of the resulting gasses. More air pressure equals a slower boil and slower vapor speeds in the column. Less air pressure results in less resistance in the column, and thus in a more aggressive boil!

There you have it: the consultant was wrong. Completely wrong. And there is a risk that many craft distillers read his article and thought they needed to be afraid of not being high up in the mountains. They shouldn't be afraid. It is 180 degrees different from how the consultant presented his conclusions. It is the sea level distilleries that are faced with the gentler boils, because the higher air pressure dampens both the boil and the speeds of the gasses exiting the liquids because of that boil.

The right attitude

You distill in a location, because you live there. Or because you expect it to be a city full of commercial opportunities. But, please, don't move up the mountain, because of this consultant's completely wrong assessment that it would lead to more gentle boils, implying "better product".

Here's what is really going on, when we compare a sea level distillery to a high-altitude location. The high-altitude distillery is faced with a more aggressive boil and higher vapor speeds in his column. This results in more smearing of heads and tails into hearts. All things equal, a higher location results in less control and a more contaminated product, that needs more aging.

There is an additional disadvantage for high-altitude distilleries. Air pressure changes and their relative influence. Sea level distilleries have a big air blanket above them. If the air pressure changes (different weather fronts coming in, for example), it changes a little bit. For distilleries at altitude, even small changes are RELATIVELY bigger, resulting in more variability in vapor speeds and more variability in smearing and flavor (like the "bumping" issue in vacuum distillation, discussed in an earlier iStill Blog post).

How to manage altitude

In order to compensate for the lower air pressure at higher altitudes, the distiller needs to power down. A lower power input results in a less aggressive boil and lower associated vapor speeds. Sometimes as much as a 50% reduction in power is needed, but this obviously depends on still type, spirit, and location.

To compensate for the higher variability in vapor speeds, in distilleries at altitude, the distiller needs to invest in a still that has power management, air pressure sensors, and automated cuts management. Power management allows the distiller to compensate for low air pressure conditions. An air pressure sensor can detect changes in air pressure, a computer can translate these changes into new cut point temperatures, and an automated cuts selector can translate these outcomes into perfect cuts, each and every time.

Hmmm ... if only there were such a still. A still with 1-100% power management. A still with seven digit accurate air pressure measurements on a per second basis. If only there is a still with a computer and software to translate air pressure changes into new cut points, instantly and automatically ... wouldn't that be an amazing innovation? If only ...

iStill's air pressure sensor measures with seven digit accuracy ...


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