The proof of a vodka listed on the label is simply double the percentage alcohol content. Proofing dates back to the British Royal Navy and the 18th century, when gunpowder was tossed into distilled spirits and ignited. A blue flame indicated that the alcohol level was in the optimal level of 114 proof, whereas too little alcohol would fail to light the gunpowder and usually hinted that the spirit had been watered down. Later, the U.S. Federal Government decided that quality spirits be bonded at 100 proof. However, higher proof vodkas, particularly for use in cocktails, retain more flavor and are becoming increasingly fashionable compared to most branded vodkas of around 80 proof.

Polish-made Spirytus vodka tops the lot at 192 proof and should remain, since the highest possible distillation for an ethanol-water mix is 94.68 percent. A higher ethanol level cannot be achieved by distillation, no matter how many times the vodka is distilled. Rubbing alcohol, by comparison, is 91 percent alcohol. Spirytus is currently the strongest liquor on sale in the U.S., having been approved for sale by the New York State Liquor Authority in 2010, at the behest of the city’s Eastern European community. Rather worryingly, it was a favorite tipple of Siberian pilots, according to legend. Because of its overwhelming strength, the vodka should not be drunk neat, however, but used instead as a “float” in cocktails.

The Pincer distillery from Glasgow makes a Shanghai Strength Vodka at 177 proof, which the producer emphasizes is not meant to be drunk straight, but used as a mixer. Accordingly, the bottle delivers 65 shots, as opposed to the customary 26, thus reducing packaging and creating what the producers term an environmentally friendly “botanical vodka,” with elements of milk thistle and elderflower. Created for the Chinese export market, the vodka’s 88.8 percent alcohol content is in homage to the number 8’s lucky status in Chinese culture.

Balkan vodka is not sold in the U.S., but it is popular in South America and in 20 other countries, where few bars will serve it without a mixer. The Serbian vodka is 176 proof and is triple distilled, reducing the level of congeners, which add aroma and taste, but concentrating the level of alcohol. The bottle comes with 13 different health warnings, including one in Braille. Despite its fearsome alcohol content, Balkan 176 is clear and flavorless, with a slightly oily texture best enhanced by storing in the freezer.