A few weeks ago I ended up in what turned into a heated debate about alcohol proof and ABV. While out drinking, a friend of a friend remarked that he had a bottle of 100-proof liquor at his house, which was, in his words “straight alcohol.” As he understood proof, the fact that it was 100 proof meant that 100% of the liquid inside was alcohol. He was wrong.
It’s a common misconception that the proof of a particular bottle of alcohol is similar to its ABV, but that just isn’t true.
Alcohol proof in the United States is twice the percentage of alcohol by volume. So, for that gentleman’s bottle of spirits, 50% of it was alcohol. In order for him to have a bottle of “straight alcohol,” he would need a 200-proof bottle, which is not a thing. The ABV of that 100-proof bottle was 50%.
In the case of most spirits, what you buy on the shelf is “proofed” using water. The United States started using proofing during the early years of the whiskey industry, when distillers would water down their whiskey so they would have more of it, and consequently be able to make more profits off their supply.
The term proofing actually comes from that time period, when people would mix gunpowder with their whiskey and then set it on fire. If it exploded, then it was “proofed.” If it didn’t, then water had obviously been added. Who would have thought having your whiskey explode would be the desired effect?
Anyway, truth be told, having water added to your whiskey (and other spirits) is something you really want to happen. If you ever tried to drink whiskey straight from the still, you’ll pretty quickly discover that it’s a bit too harsh for general consumption. Water mellows the spirit out and makes it drinkable. Trust me, it’s a very, very good thing.