Overproof Rum

Overproof rum is rum whose alcohol content is higher than a standard value, known as proof.

Although the word proof is currently used as a measure of alcohol content, it was originally used in 18th century Britain to refer to a specific value of Alcohol By Volume (ABV), 57.15% to be precise.  Of course, nobody sat down and came up with this number.

Rather, the method used to test for proof involved pouring a little of the target liquid over some grains of gunpowder and setting it alight. If the mixture remained alight, then the liquid was said to be at proof. If, on the other hand, the liquid did not remain alight, the mixture was underproof. Finally, if the liquid was stronger than proof, then the gunpowder would explode (not much, I hope). This received the name overproof. Later on, the proof ABV was found to be the magic number mentioned above, 57.15%. This became known as 100 proof later on, when the term proof turned into a measure of alcohol content as opposed to a fixed value.

So of course, the term overproof rum refers to any rum stronger than that. The most common overproof rum is 151 proof, which refers to about 75% ABV. If you’re paying attention, you’ll note that if 57.15% is 100 proof, then 151 proof should be 86.3%, not 75%. What’s the deal with that?

Well, the deal is that there are two definitions for proof. The original version, used in Britain, specifies that the ratio of proof to ABV should be approximately 7:4, whereas the alternative version, used in the USA and by extension almost everywhere else, simplifies this as 2:1. If you calculate the ABV of 151 proof using the american version, you get the aforementioned 75%.

At this strength, the rum is fairly lacking in flavour. The alcohol dominates and it takes a brave person to drink it straight. But it is used frequently in tropical cocktails, usually as a way to strengthen a fruity drink without having to add more volume of spirits and ruining the balance of the drink.

Not an essential bottle in your bar, but useful for all those tropical drinks.