Distilling Top-Shelf Whisky is All About Vapor Speed!

Introduction

Distilling top-shelf whisky in potstill mode is all about vapor speed. Better said: distilling top-shelf whisky, brandy, gin, rum and any other taste-rich spirit is all about vapor speed. To be even more precise: distilling top-shelf taste-rich spirits depends on cuts for heads, hearts, and tails, on and vapor speed. This iStill Blog post dives into vapor speed; the variable less well-known than cut points.

Today, I want to teach you on how vapor speeds influence flavor composition and on how certain pot distilled drink-categories benefit from higher, medium, or lower vapor speeds. Finally, I want you to learn more about vapor speed control. I mean, a better understanding of the importance of vapor speed is one thing, but how does one apply that knowledge into the production of higher-quality whisky, gin, rum, or brandy? Via control over vapor speeds. Let's dive in deeper via an example!

An example

We are going to talk pot distilled whisky here, but please know that the framework presented here is just as applicable to other taste-rich, pot distilled spirit. I'll focus on whisky to save on words.

So, here's the example. Imagine you do a finishing run on a single malt whisky. Your cut points for heads, hearts, and tails are 81 degrees Centigrade, 94 degrees Centigrade, and 97 degrees Centigrade. You collect the heads faction until the temperature in the column is 81C. You then collect hearts until 94C. You collect tails until 97C and then stop the run.

A definition of vapor speed

In essence, a distillation device consists of three parts. A boiler, where an alcohol-rich fluid is brought to a boil. A boil that produces gasses. The riser or column that transports these gasses away from the boiler. Towards the cooler. And then, finally, the third component: the cooler. The cooler collapses the gasses back to liquid phase. Important, as we are producing alcoholic beverages, not alcoholic gasses. :)

So there you have it: liquids turn to gasses that turn into liquid. And as most alcohol molecules are "lighter" and have lower boiling points than water, the gasses produced by the boiler have a higher alcohol content. Thus we make alcoholic spirits. Now what about that definition of vapor speed, Odin? Almost there ...

Before we get there, I want you to take in one more thing: the phase-change from liquids (in the boiler) to gasses (in the column) and back to liquid (in the cooler) is not a one-on-one change. Volume-wise amazing things happen during those phase-shifts. Gasses, when formed, hugely expand in volume. Liquids, when formed, hugely contract in volume. By no less than a factor of 100! Imagine that you distill - let's say in a minute - a cup of liquid. That cup translates into a volume of 100 cups of vapor. As columns or risers are smaller, both in volume and diameter, than boilers, it is now easy to see that the liquid to gas phase-change results in those gasses speeding up and moving through the riser or column at relatively high speed.

The definition of vapor speed? The gas speed inside your column or riser, while you are preforming a distillation run. Now, let's dive into the influence of vapor speed on flavor.

The influence of vapor speed on distilling

Vapor speed influences many things related to the creation of taste-rich spirits. Here is a summary:

1. Heads smearing;
2. Tails smearing;
3. Water smearing.

Heads smearing and vapor speed

The heads faction consists of low boiling point alcohols and associated fruity esters. Given the statically defined cut points mentioned above (81c for heads, 93c for hearts, and 97c for tails), what happens if you distill with higher vapor speeds? The higher speeds will concentrate more of the hearts-associated ethanol in your heads cut. Do to the higher vapor speeds, hearts will bleed into heads, both contaminating the heads cut with good alcohol, and leaving more headsy alcohols and flavors behind, to be blended into your hearts cut.

Higher vapor speeds result in more headsy alcohols and fruity flavors being smeared into your hearts cut. The result? A more flavorful hearts cut, because that faction is now contaminated not just with the grain flavors that associate with hearts, but also with the fruitiness of the additional heads smearing.

Just as higher vapor speeds result in more heads smearing into hearts, lower vapor speeds result in less heads smearing into hearts. Lower vapor speeds result in a better separation of heads, where headsy alcohols and their associated fruity taste molecules stay in the heads cut and do not blend over into hearts.

As a general rule, we can conclude that faster vapor speeds result in more heads smearing into hearts. Lower vapor speeds result in less heads smearing into hearts.

Tails smearing and vapor speed

Higher vapor speeds result in the earlier selection of "heavier" or higher boiling-point alcohols coming over. High boiling-point alcohols associate with earthy, rooty, nutty flavors. High vapor speed distillation therefore results in earlier tails smearing. As a result, the hearts faction, at those higher vapor speeds, gets contaminated with more tailsy alcohols and earthy, rooty, and nutty flavors earlier.

Lower vapor speeds have the opposite effect. They allow for a better separation between the hearts and the tails faction. Less smearing and a cleaner hearts cut, where the substrate flavors of hearts are not overpowered by the rooty, nutty, and earthy flavors.

As a generic rule, we can now conclude that faster vapor speeds result in more tails smearing into hearts. Lower vapor speeds result in less and later tails smearing into hearts.

Water smearing and vapor speed

Finally, as water is a "heavier", higher boiling-point molecule than ethanol, the alcohol most present in your hearts cut, it is important to understand that vapor speeds in your riser or column also influence the amount of water that gets smeared into your run in general, and into your hearts cut specifically.

Contrary to heads and tails smearing, water has no flavor. But higher or lower vapor speeds still have an influence. In potstill runs, higher vapor speeds result in more water coming over. Lower vapor speeds result in less water smearing. In plain English? Higher vapor speeds result in lower ABV output.

What vapor speeds are ideal for whisky?

I define whisky as a three-dimensional drink, where the substrate that it is made from can be identified. This means that all three flavor boxes need to be ticked off. Whisky needs to have a fruity beginning, a middle where one tastes the grain, and a long finish with earthy, rooty, and nutty flavors. In order to get the right amount of smearing, higher vapor speeds are needed to produce interesting whiskies.

Vapor speed control

In general, whisky is distilled on a potstill with a relatively slender riser or column. The small diameter results in higher vapor speeds. The higher vapor speeds enable the smearing of heads and tails into hearts.

Given your set-up is what it is, another approach to improved whisky distillation is that you distill faster. Push the power that goes into the boil upwards, so that you create more gasses that need to travel through the same column or riser ... resulting in higher vapor speeds and more smearing.

Or simply purchase an iStill, as it is the only still with a fully optimized design for vapor speed control. Yeah, that's the tool you need if you want to produce top-shelf flavor-rich spirits. The iStill Hybrid even allows you to make whisky in one single go in column mode ... for even more taste! More on that in a later post.

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