As bartenders continue to reach ever deeper into the annals of mixology, they've become increasingly obsessed with obscure historical cocktails, developing a flair for ingredients like egg whites and absinthe. Now many are gravitating toward soda-fountain drinks for inspiration. Thus, we're seeing drinks made with lactart (a natural acid found in yogurt and buttermilk) and acid phosphate (a shelf-stable substitute for citrus juice common in the days before heirloom limes could be flown in daily all winter long).
These aren't mainstream, 1950s Norman Rockwell drinks. Way back in the 1890s, the soda fountain doubled as a pharmacy and was staffed by chemists. You could sit along the counter and drink a glass of stomach-settling seltzer water or get your bitter-tasting meds mixed with sweet, fizzy drinks. Like the song says, a spoonful of sugar (and acid phosphate) makes the medicine go down. But we're not talking Fred Flintstones vitamins. Turn-of-the-century doctors regularly prescribed cocaine, heroin, strychnine, opium, and morphine, which they made palatable with the tongue-tingling, dry tart flavor of acid phosphate.
That's the flavor profile as described by Darcy O'Neil, a Canadian bartender-chemist who researched the unsavory history of the soda fountain for his 2010 book, Fix the Pumps, and then packaged powdered acid phosphate to sell to modern-day bartenders. Now you'll find acid-phosphate drinks at faux-vintage soda fountains like Philadelphia's Franklin Fountain, which serves the Japanese Thirst Killer Phosphate, or San Francisco's Ice Cream Bar, where the Angostura Phosphate is making a comeback. Even non-time-traveling bars are trying their hand at drinks like the Cherry-Ginger Phosphate topped with ginger beer at Still & Stir in Worcester, Massachusetts.
At Honor Kitchen & Cocktails in Emeryville, California, acid phosphate makes an appearance alongside sherry, gin, amaro, and absinthe in the Guy Fawkes. At the Russell House in Cambridge, Massachusetts, it's combined with scotch, Benedictine, and pear liqueur in the coquettishly named Let Me Draw You. Even home bartenders are experimenting—with ingredients like vinegar, citric acid, and lactart—because ultimately most cocktails, even the sweet and chocolate varieties, benefit from a hit of acid.
—Camper English is an international cocktails and spirits writer and the publisher of alcademics.com.