I often mention alcohol proof. Alcohol proof is a measure of how much alcohol is contained in a beverage.
The term was originally used in the United Kingdom and was defined as 7/4 times the alcohol by volume (ABV).
The measurement of alcohol content and the statement of this content on the bottle labels of distilled beverages is regulated by law in the United States. The purpose of the regulation is to provide pertinent information to the consumer.
The European Union currently follows recommendations of the International Organization of Legal Metrology (OIML). OIML’s International Recommendation provides standards for measuring alcohol strength by volume and by mass. A preference for one method over the other is not stated in the document, but if alcohol strength by volume is used, it must be expressed as a percentage (%) of total volume, and the water/alcohol mixture must have a temperature of 20°C (68°F) when measurement is done. The document does not address alcohol proof or the labeling of bottles.
Alcohol proof in the United States is defined as twice the percentage of alcohol by volume. Consequently, 100-proof whiskey contains 50% alcohol by volume. Recently the United States has begun to label bottles containing wine and spirits with the percentage of alcohol by volume, instead of proof.
Britain, which used to use the Sikes scale to display proof, now uses the European scale set down by the IOLM. This scale, for all intents and purposes the same as the Gay-Lussac scale previously used by much of mainland Europe, was adopted by all the countries in the European Community in 1980. Using the IOLM scale or the Gay-Lussac scale is essentially the same as measuring alcohol by volume except that the figures are expressed in degrees, not percentages.
Alcohol by volume may be the more accurate and modern method but I’m an old coot and proof is what I learned so I tend to use that as my touchstone so forgive me if I suddenly throw that term around.
It’s good to be forewarned about the differences you’ll encounter when purchasing alcohol so you’re not accidentally purchasing something either too weak or too strong for your needs.
Until next time, may all your drinks be tasty. Cheers.