The Simple Reason Most Bourbon Is Distilled Twice

Whiskey is, perhaps, one of the most complex and diverse spirits in the world. Depending on where, from what, and how it's made, there will be marked differences in its color, flavor, and aging period, resulting in a wide variety of bourbon profiles. However, in the process of making whiskey — whether it's in Scotland, Ireland, or the United States — a very important piece of the puzzle is distillation. And in order to produce the best, cleanest whiskey possible, it is often necessary to distill the spirit at least twice. The reason is simple: A double distillation increases the alcohol content, removes impurities, and concentrates and refines the flavors of the spirit. This, of course, includes Bourbon.

The process of double distillation, as the name implies, consists of two steps. In the first, the fermented mash is distilled to elevate the alcohol level, usually from 6%-10% alcohol to around 25%-30%. This first run can be done in a column or in a pot still. A second distillation run through a copper pot still further raises the alcohol level and removes impurities from the spirit. At this point, masters distillers separate the heads (the first liquid resulting from distillation) and tails (the liquid at the end of distillation), keeping only the liquid from the middle of the run. The resulting spirit is clear and strong, and it's commonly known as white dog or new make spirit. It is then cut with water to the legal alcohol content requirement of 80% ABV before placing in barrels to age according to very strict rules.

While larger distilleries use column stills (at least for the first distillation), most craft producers rely on copper pot stills for both distillations. These are the most traditional type of stills, and they work on what distillers call a "batch system". This means that after the first distillation run, the still needs to be emptied and thoroughly cleaned before starting the second distillation, which makes it a much less efficient process than continuous distillation (which is not the same as triple distillation) in a column still. However, it results in a richer, full-flavored new make spirit that yields a tastier Bourbon.

Pot stills are simpler and less expensive than column stills, so they are usually the choice for smaller companies such as craft distillers. While there are many factors that contribute to the taste profile of Bourbon, including the mash, water, yeast, alcohol content at bottling, and the time and char level of the barrel used in the aging process, double distilling is crucial in crafting a high-quality Bourbon. There are a few clues you need to follow to know whether a Bourbon is of low or high quality, so do your homework before you head to the store shelves.