On any bottle of Whisk(e)y, you’ll see various pieces of information: the Name, Brand, Style, Size, sometimes a bit of history on the company or the way this particular drink was aged (finished in red wine barrels or a selective use of first fill American oak casks, for example), maybe a batch number or that it’s non-chill filtered, and so on. Something that’s required by LAW to have on the label is the Alcohol content. This is often seen as ABV, Alc/Vol, Alc. by Vol., and it’s sometimes also shown in conjunction with Proof.
If you take a look at a bottle (such as this Uncle Nearest 1856) you’ll see it says 50% ALC/VOL along with 100 PROOF. Because we’re clever connoisseurs, we could assume that Proof is just double whatever the ABV is. And, you’d be right – if you’re looking at an American bottle of spirit. Hop across the pond, however, and their ratio is slightly different, which I’ll get to in a moment.
But WHY? WHERE did the word PROOF actually originate?
Let’s take a trip back in time, to 1500s England, where spirits were taxed at different rates, depending on their alcoholic strength. Higher strength = higher taxes. Now, they didn’t have the fancy scientific gear of Today, like alcoholmeters and hydrometers; so, how exactly did they test for alcohol content?
Well, turns out their method wasn’t exact at all. They would take a pellet of gunpowder and soak it in the spirit; if the pellet was able to then be ignited, this was PROOF that the spirit had 57.15% alcohol or higher and therefore able to be taxed at a higher rate. And because this is England, that 57.15% mark = 100 Proof, so roughly 1.75 times the alcohol vs America’s 2.
This top notch, completely reliable, easy to replicate method (please note the tongue-in-cheek sarcasm here) fell out of fashion fairly quickly. By the early 1800s, a newer method based on gravity was the norm in the UK; but around 1848, America decided to base their Proof system on Alcohol % rather than specific gravity. As 100 Proof was always the agreed upon basis for over/under Proof for taxation, America decided that 50% ABV equalled 100 Proof.
Although based on fun origins worthy of retelling at a party to PROVE how much you know (see what I did there?) about alcohol, the use of Proof as a way of measuring alcohol content is now mainly relegated to the history books.