Humidity has met its match. Thermal reconditioning, a six-year-old Japanese hair-straightening procedure, is sweeping the States as the pin-straight look proves its fashion longevity. ”I’ve had women say it changed their lives,” says Sonja Sartorius (arrojostudio.com), who has been performing the hair operation for two years. Julianne Moore, Lauren Graham, and Tyra Banks have all undergone thermal reconditioning ($350-$850), which uses an acid-based solution and irons heated to 180 degrees. The procedure requires touch-ups every three to six months and takes up to six hours, but sleek-locked converts rave that their reconditioned hair air-dries perfectly straight and stays silky even in a sauna. But buyer beware, warns Sartorius, who worries that too many untrained stylists are setting up shop. ”Definitely consult several technicians before making your final appointment,” she advises. Damn straight.