An alarming number of wines become "corked," or moldy—possibly as many as 15 percent. Napa Wine Co., which crushes grapes and blends and bottles wines for boutique Napa Valley producers such as Pahlmeyer, is aiming to change that by topping some of its most prestigious wines with screw caps. The man behind this move is 49-year-old Andrew Hoxsey, an owner and managing partner of Napa Wine Co. and a fourth-generation grape grower who began running the family business in 1984 after working as a pilot. Last March, without even gauging interest from clients, Hoxsey installed a second bottling line for screw-cap enclosures. "It was a shoot-from-the-hip decision," he says. Napa Wine Co. has since won over several important converts, including PlumpJack, Voss and Silverado Vineyards. And the number keeps growing: Hoxsey will use screw caps on more than 125,000 cases this year, more than a six-fold increase from the year before.