Alcohol distillation is the process of isolating ethanol from other components found in fermented alcoholic beverages through heat and pressure; alcohol’s lower boiling temperature compared to water allows this separation. As liquid is heated it changes to steam which, when cooled down, condenses into vapor containing all the alcohol-containing components of a beverage. This vapor is then separated from its source liquid and collected into containers for later collection. Early stills were simple pot stills that are still used today for some bourbon production. By the late 18th century large scale distillers began using columns composed of several vaporization chambers stacked one on top of another to increase control of separation processes and provide for greater precision during distillation.
Alcohol vapor is drawn off the top of a still and sent through a series of ascending plates which provide surfaces which force any molecules in the vapor back down into liquid, and removing their alcohol content through what is known as a reflux operation. As each plate becomes cooler than its predecessor, heavier molecules (e.g. methanol) condense at the bottom while lighter ones float up through the column until collected by gravity.
At this point, distillation becomes an art. According to Harold McGee in On Food and Cooking, distilling requires skillful timing – an experienced distiller must determine when they should stop collecting heads and hearts in order to create the ideal blend of ethanol and congeners for their spirit’s proof level; its proof directly affects its flavor; vodka being distilled to 94% ABV has much purer ethanol content but no detectable flavors while cognac requires higher proof levels and contains more congeners that add complexity in flavor than its vodka counterpart; therefore cognac needs higher proof for best flavor development.
