This summer, I conducted a series of backyard experiments involving gunpowder and spirits. For each trial, I poured old-fashioned black gunpowder onto a plate, dampened it with a bit of rum or gin or some other liquor, and then applied a flame. Sometimes this resulted in a satisfying flash, followed by a small cloud of acrid smoke. Other times, nothing.
The experiments were a little bit of chemistry, and a lot of history. Centuries ago, British sailors supposedly used gunpowder to determine whether their daily tot had been watered down by an unscrupulous purser. Pursers were widely assumed to requisition a portion of official rum supplies for personal use, and to top up the casks with water. Sailors believed that gunpowder splashed with watered-down liquor wouldn’t combust, while liquor containing more than 50 percent alcohol by weight would cause the powder to flare. If it did flare, the liquor was “proved,” giving rise to the term proof. If it didn’t, the purser might find himself tossed overboard. This was known as the “gunpowder proof test,” and I was curious if it would actually work.
In my home tests, the results were inconsistent and wholly mystifying. I learned that Lemon Hart 151-proof rum (75.5 percent alcohol) would always flare, but other spirits, including Plymouth Navy Strength Gin (57 percent), ignited only occasionally. At times, even liqueurs, with considerably lower proofs, would unexpectedly blaze up. The inconsistency may have resulted from the humidity on the days I tested. It may have had to do with my efforts at quality control, which involved an occasional nip of the test product. But it made me wonder if pursers had been unjustly given the heave-ho in humid environments, or if the gunpowder test was possibly spurious altogether. One vendor of black powder I spoke with speculated that the practice might have had a scientific basis—something to do with the potassium nitrates in the gunpowder being soluble in water but not in alcohol. My research will continue as long as I have musket powder and fingers.