So why use the term proof? What is there to prove? Well there’s a great deal to prove to a thirsty buccaneer.
Alcohol proof measures the amount of alcohol contained in a beverage. In the United States proof is equal to twice the percentage of alcohol by volume. An 80 proof bottle of vodka would contain 40% Alcohol by Volume (ABV).
The term dates back to the 1600’s when colonial empires were forming and seaborne trade developed throughout the world. Life at sea was difficult. Alcohol in the form of rum was added to water rations as a believed preservative. Rum was considered a needed provision to boost moral during long dangerous voyages for both Naval Sailors and Pirates. Payments to British Sailors even included rations of rum.
Rum makers often watered down the spirit in an effort to profit more on each bottle. This could be a very dangerous practice when selling to pirates. Pirates and Naval Sailors used a very creative way to prove a distilled spirit contained at least 57.15% ABV.
The sailors would use a simple test involving torching Gunpowder doused in Rum. Gunpowder alone will ignite in a flare like manor when torched with a flame. Gunpowder doused with a distilled spirit will only flare up when alcohol content is at least 57.15% ABV. A spirit with higher water content will only wet the powder to a point it will not ignite.
So there’s the proof, a simple test any good buccaneer should know.