The Compendium of Bar Measurements and Terms, Part 3

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The Compendium of Bar Measurements and Terms, Part 3

-By Dr. Ron A. Ñejo

ABV

ABV or Alcohol By Volume is a very common way of characterizing the concentration of an alcoholic beverage. It represents the percentage of pure alcohol (anhydrous alcohol) present in a solution, at 20 degrees Celsius. The temperature is important because alcohol expands more than water at higher temperatures.

G.L.

In some countries, the alcohol strength is displayed as degrees “G.L.” or “Gay Lussac”. This nomenclature tends to be used interchangeable with ABV, but in reality they are not 100% equivalents, since the Gay-Lussac measurements are all based at 15 degrees Celsius.

Proof

Another way of specifying the amount of alcohol is alcohol proof, which in the United States is twice the alcohol -by-volume number, while in the United Kingdom it used to be 1.75 times that number. However, since 1980, alcoholic proof in the United Kingdom has been replaced by ABV as a measure of alcohol content.

Where did the term “Proof” come from?

Perhaps the best explanation I’ve ever read came from Dr. William B. Jensen, from the Department of Chemistry from the University of Cincinnati. According to him, the term originated in the 16th century in England from the need to tax the liquor producers (not surprisingly):

“The original test involved soaking a pellet of gunpowder with the liquor. If it was still possible to ignite the wet gunpowder, the alcohol content of the liquor was rated above proof and it was taxed at a higher rate, and vice versa if the powder failed to ignite.”

Towards the end of the 17th century, the notion of measuring the strength of alcohol through its specific gravity had already been suggested, but since this measurement was so dependent on precise temperature, it was not widely relied on.

In 1816 the standard of proof was defined in England as being 12/13th the specific gravity of distilled water at the same temperature. In the USA, on the other hand, proof was defined in 1848 solely based on ABV and not on density, taking as a standard a distilled spirit at 50%, which became the “proof ”. In the USA a “proof gallon” is a gallon of a distilled spirit at 50% ABV and is still the base for all alcohol taxation.

Next month: Measurements