We have now created a wash with an alcohol content of around 5-10% ABV and employed a series of techniques to ensure the desired aroma compounds are present in the liquid. The next step is distillation, a process that involves the separation, selection, and concentration of its individual parts, sometimes referred to as fractions or cuts.
Although the composition of a rum wash is mostly ethanol and water, there are countless other factions, some of which provide flavor and some are, more or less, poisonous. For the sake of brevity, we will divide these fractions into three groups: Heads, Hearts & Tails.
In practical terms, a distiller uses boiling and condensation in order to concentrate and select the desired cuts. The fermented wash is heated in a closed vessel until it starts to vaporize and this steam travels up the still. The vapor is then cooled down and the resulting condensation is transformed back into a liquid form.
Heads is the first cut from the still and consist of the compounds with the lowest boiling point, like ethereal aromas, and methanol.
The Hearts cut is next to vaporize and contains most of the ethanol and preferable aromas. The Tails are comprised of heavier alcohols and aromatics with a high boiling point.
The challenge for any distiller is to adjust their Hearts cut to retain as much ethanol as possible, along with the desired congeners, while excluding as much methanol, sulfur, or heavier alcohols. This is where skill, preference, and olfactory sense of our master distiller come into play.
In the next chapters, we will dive deeper into the two types of distillation: Batch- & Continuous-distillation.