Distilling Top-shelf Rum is all about Vapor Speed!

Introduction

For an introduction on vapor speed, and its importance to distilling top-shelf taste-rich products, please read this first: https://istillblog.com/2024/02/07/distilling-top-shelf-whisky-is-all-about-vapor-speed/

A summary on vapor speed

Higher vapor speeds result in more heads and tails smearing. Lower vapor speeds result in less heads and tails contamination of your hearts cut. Higher vapor speed distillation result in more three-dimensional spirits, where lower vapor speed distillation runs result in less contamination and a cleaner less tasty product. In double distillation approach, potstill-style, managing vapor speed is king.

The relation between rum varieties and vapor speed

Rums can be classified in high-ester rums, medium-ester rums, and light rums. Light rums have less taste molecules. What is highlighted in a light rum is the molasse or sugar cane flavor, that sits in the middle of the run, in your hearts cut. Light rums taste of the substrate the rum is made from and not much else. The production of light rum benefits from low vapor speeds, as these allow for a good separation of heads, hearts, and tails. The lack of heads and tails contamination results in a clear sugar cane or molasses flavor. Yes, quite one-dimensional, but that's why it is a lighter style rum.

Medium flavor rums have more flavor than light rums. There are some fruity flavors at the beginning and some rooty, nutty flavors at the back. A perfectly made medium-ester rum has as much fruity esters and rooty, nutty esters as it has substrate-related hearts flavors. Medium vapor speeds allow for more smearing of fruity flavors, and of rooty and nutty tails-associated flavors into hearts. Medium vapor speeds make great medium flavor rums.

A high-ester or heavy rum has an overdose on both fruity and rooty, nutty, and even earthy flavors. The way to get there, in a double distillation, potstill distillation protocol - as far as vapor speeds are concerned - is that you distill faster. Faster runs result in higher vapor speeds and higher vapor speeds result in more smearing of heads and tails into hearts. Yes, the product will take more time to age and to mellow out, but it will become a more interesting, three-dimensional product in the end!

On flavor intensity and vapor speed

As a generic rule about 30% of the esters - of flavor molecules - are heads associated. Only 20% of the esters in any drink are hearts associated. The remaining 50% of flavor can be found in the tails that smear into hearts.

The above knowledge creates a nice model that helps understand how much the difference in flavor intensity and length can be, when we compare the various rum categories:

• Light rum can have up to 20 ppm of flavor molecules - that's 20 esters per one million molecules;
• Medium rum can have up to 60 ppm of esters - 20 heads, 20 hearts, and 20 tails associated;
• High-ester rum has at least 100 esters per million molecules - 30 heads, 20 hearts, and 50 from tails.

Look at those numbers again, and realize that medium rum has two to three times more flavor than light rum. High-ester rum has 5 to 6 times more flavor than light rum. And all you need to make those three very distinct products from one and the same ferment ... is an understanding of cut points and vapor speeds.

How to get there? How to create the rum of your choice? Well, a finishing run on a power setting of 30% allows you to cut a great light rum. Are you into medium-taste rums, then put the power between 40 and 50%. For a high-ester rum, push your iStill to 50-60% power. As an alternative method, you can also go for a wider hearts cut, as it also allows for more heads and tails smearing.

Please understand that 100 ppm rum is the minimum threshold for what I consider to be high-ester rum. Wanna go higher in taste, as far up as 300 to 600 ppm? Backset-cycling and the Maillard Reaction will get you there. Do you want to learn how these work? Purchase an iStill. It comes with our online educational facility included. We don't just sell you the still, we also educate you to become the best craft distiller you can be.

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