You probably noticed an alcohol's proof is twice the alcohol content of the bottle, but really, what does proof of alcohol mean? "Proof" is one of those alcohol buzzwords you probably think only bougie people use to describe the alcohol content of liquors.
If you're anything like me, you think that including the proof on a label is the most pointless thing in the world. Why the heck do we need the amount of alcohol on the bottle twice? While there may or may not be a reasonable explanation, an alcohol's proof can tell you a lot about what's inside your bottle.
The Origin of "Proof"
This one still remains a mystery to historians. Some claim that the term originated from the British Royal Navy regarding rum in the 18th century, while others say it's a result of practices done to test whiskey made by farmers in America around the same time.
Either way, the term "proof" definitely comes from a test that was done to test the amount of alcohol present in liquor. The liquor was mixed with gunpowder and set on fire. If nothing happened, the bottle was said to be watered down. If there was some sort of ignition or explosion, the bottle was "proofed" to contain an acceptable amount of alcohol.
In the US, our proof system was established around 1848, where alcohol containing 50% alcohol was defined as 100 proof for tax purposes. Thus, doubling the alcohol content to derive an alcohol's proof began. This was a completely arbitrary standard picked because liquor with a 50% alcohol content was considered pretty normal for strong liquors. Taxes were determined based on how much higher or lower the proof of the bottle was relative to 100 proof.
Proof Labeling
If the reasoning for our proof system wasn't enough to make you question its validity, wait until you learn that alcohol isn't even required to be labeled with its proof. Some liquors are defined by their proof but are commonly preceded by the percent alcohol content the proof represents. Alcoholic beverages are always required to express the alcohol content in percent alcohol on the bottle.
So why do we keep printing the proof on the bottle? Sentiment? To preserve a small part of history? It seems like a case of "we always have so we always will." If anything, knowing its origin gives you a great story to tell at parties. Maybe it'll inspire you to responsibly light up your liquor, you know, for science.
The Lowest Proofs
As redundant as it seems, many people talk about and define alcohol by their proof. Any alcohol can be talked about in terms of proof, but beer, wine, and other low-alcohol beverages usually aren't defined by their proof. The term is typically reserved for liquors, which vary much more in alcohol content than different types of beer do.
The liquors that can have the lowest proof and still be defined as liquor are any bottles of flavored brandy, gin, vodka, rum, and whiskey. They can all be diluted to down to 40 proof and still fit into their legal definitions.
This is good news for those of us who are looking to have a great tasting drink sans hangover the next morning. Generally, choosing a flavored liquor will get you a lower proof bottle. Malibu is 42 proof, Smirnoff's and Burnett's-flavored vodkas are typically around 70 proof, and Fireball is only 66 proof. All of these are much weaker than their unflavored, pure counterparts, which must come in at no lower than 80 proof.
The Highest Proofs
Even though true liquors can contain as low as 80 proof, they can also go as high as 192 proof. The honor of highest proof alcohol goes to Spirytus vodka, a Polish vodka that contains 96% alcohol. Close behind comes Everclear, which is 190 proof. Both are
(mostly) legal in the US and are considered borderline dangerous.
The higher the proof, the more calories per shot you're consuming. You'll also be prone to more severe hangovers and become intoxicated faster. That last part sounds fun, but the more you drink, the heavier you tend to pour, and nothing screams alcohol poisoning like a few shots of 95% pure alcohol. Not to mention alcohol above 101 proof is considered flammable and the typical presence of lighters at parties can pose a danger.
That's not to say these high proof liquors can't be responsibly enjoyed. Though you may want to consider Sunset Rum (169 proof), Bacardi 151 (151 proof, if you didn't know), or Booker's Bourbon (130 proof) to get your fix of higher proof liquors. Luckily, alcohol with strong proofs tend to think of this characteristic as a bragging right, so they're very clearly labeled with their alcohol content.
The fact that everyone still lists proof on bottles may not make a whole lot of sense, but knowing the term came from igniting liquor to see if it catches on fire makes it acceptable in my eyes. For now, it looks like we'll keep on defining liquors by their proof, so it helps to know that grabbing a bottle of Bacardi 151 will have a much different effect on you than Bacardi Razz (which is 64 proof, if you're interested).