Any whiskey enthusiast knows that distillation is the process of taking fermented liquid and extracting only its alcoholic components, called “wash.” This can be achieved due to alcohol (ethanol) boiling at a lower temperature than water (212 degrees Fahrenheit), meaning when heated liquid, only alcohol vaporizes when heated; then as this vapor rises through a still’s swan neck or “lyne arm”, it encounters a coil submerged in cool water which condenses it back down into liquid form, which now contains much higher concentration of ethanol than original wash!
During this process, less desirable or harmful substances, like fusel oils and THMs, are also vaporized along with the ethanol, giving the finished spirits their signature flavors such as fusel oils and THMs. Due to their very low boiling points and subsequent release from their vaporisation through distillation processes, proof levels at liquor stores will often be significantly lower than what you’d find at craft distilleries; hence the term “reflux”.
Reflux plays an essential part in helping a distiller achieve high purity in their final product, since molecules vaporizing and condensing determine its character and quality. Distillers will use experience, intuition and artistry when making decisions regarding when to stop distillation.
