Aspects of Distillation (1): Air Pressure!

Introduction

“Aspects of Distillation” is a new series the iStill Blog will host. It aims to cover as many aspects as possible. Aspects of – you guessed it! – the distillation process. Think alcohol formation, flavors, mashing, distillery design … and more. In fact, if you have a suggestion, please email us the aspect you want us to dive into. Via Odin@iStillmail.com. Today’s topic? The influence and importance air pressure has on distillation.

Air pressure

There are three things I want you to consider, when investigating air pressure and its role in the distillation process:

  1. Air pressure directly influences the flavor composition of the drinks you produce;
  2. Air pressure constantly changes;
  3. So changing air pressure constantly changes the flavor composition of your drinks.

Starting this investigation with air pressure variability, I want you to understand that higher altitude results in lower air pressure. Also – at any altitude – air pressure changes constantly.

When you make drinks like gin, whiskey, rum or brandy, you cut for heads, hearts, and tails. The best way to measure and replicate cuts is by looking at the temperatures in the column or riser of your still. Do you cut from heads to hearts at 82c? Good, you now have a reference point to do the exact same run again tomorrow, and create the exact same cuts again, by using 82c as the switch-point from heads to hearts, right? Wrong.

As air pressure constantly changes, so do associated boiling points. In other words: given yesterday’s air pressure, the 82c cut-point may have been spot-on. But what if air pressure is lower, due to a bad weather front moving in? What was a good decision at 82c yesterday, may need to be 81.6c today.

Now, 0.4c degrees difference does not sound like a lot, but look at it this way: if it takes your still 25 minutes to move up in temperature 0.4c … that now means you either have collected 25 minutes of heads into your hearts, or that you just lost 25 minutes of good product to a badly judged heads cut!

Cut management via a parrot and ABV only deepens the problem. Cut management by taste is very subjective and influenced by what you ate, so no solution either. So how can this problem, that hugely influences flavors and therefor the consistency of craft distilled spirits, be solved?

Feature

iStill designed an air pressure sensor. It measures the air pressure every second. If the air pressure changes, the sensor informs the computer. The computer then automatically adapts your cut-points to compensate.

If we use the above example, with yesterday’s heads to hearts cut taking place at 82c. Today, you want to replicate the same recipe, so you look it up in your product library, load it into the iStill computer, and tell the iStill to start executing. The air pressure sensor notices immediately (and constantly) that the air pressure – relative to yesterday – is 0.4c off. As a result, the computer automatically changes your heads to hearts cut from 82c to 81.6c. If the air pressure monitor sees a change from 0.4c to – say – 0.3c, the heads to hearts cut will immediately compensate to 81.7c instead of 81.6c.

Benefits

All iStills are equipped with air pressure sensors and the resulting dynamic cuts management for heads, hearts, and tails. It is a standard feature to our stills. It helps craft distillers make better product, more consistently, and with less guessing, effort and supervision.

iStill’s amazing air pressure sensor …

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