distilling

Distillation requires both extreme precision and intuitive skill to produce quality spirits, with every distillation increasing or diminishing some flavor molecules (esters and congeners) while eliminating others. Achieve 95+ proof spirits may require multiple runs through the still to reach that perfect result – each run may introduce new compounds which alter its final product. It’s important to keep in mind that alcohol and water make up only 40% of a starting liquid’s composition; most flavors make up at least another 40%, each having their own volatility that allows us to separate out those compounds that make up a finished bottle of spirits.

Starting liquid is heated in a steam generator before passing through a series of perforated plates – often made of copper – acting like miniature pot stills. As hot steam passes over each plate, its vapor is separated into different fractions; those coming off of the first plates, known as heads, contain volatile compounds with the lowest boiling points such as methanol, wood alcohol or wood naphtha; all have unpleasant or harmful aromas and tastes and could potentially be toxic to human beings, leading to blindness if consumed.

Hearts contain more desirable ethanol alcohol, and it is the distiller’s responsibility to redirect vapor flow from the head section into this part by altering its reflux ratio; increasing this ratio allows more vapor through and decreases head percentage; however, doing so increases energy costs.

Balance of Proofs in Distilled Spirits Most spirits sold today are bottled at 80 proof alcohol by volume for taxation reasons and this seems to be a popular consumer preference; however, certain single malt whiskies and aged gins offer greater flavor at higher strength concentrations.

Distillers use hydrometers (gauges) to precisely determine the proof of spirits. A liquid sample is placed into a test jar or parrot, then its reading compared against an associated chart of temperature corrections – the figure on the right of said chart corresponds with its hydrometer reading indicating its true proof level.

But that’s only half the battle; to achieve proof, knowing exactly how much water needs to be added is also essential – which is where tables come into their own.

Weighing is a legally required step for most craft distillers, where empty container weights (tare weights) are subtracted from observed (total) weight to calculate net weight and thus tank content. Tare weights can then be converted to gallonage using TTB’s Gauging Manual.

Proof originates in British naval tradition of allocating daily rations of rum to sailors. When doing this, they would use gunpowder soaked into the liquid as proof that it could ignite. Once this tradition spread, consumer safety and taxation purposes also used this system for other spirits as proof.