Though high temperatures can wreak havoc with hair, a spot for Unilever's heat-activated Thermasilk shampoo maintains "Heat is beautiful." The mythologically themed ad, breaking this week on network TV, features a beautiful Medusa whose snake-locks transform as she tangos with a fiery warrior, and gods and mortals alike look on. J. Walter Thompson USA, New York, is the agency. Copywriter: Chris D'Rozario. Art director: Ed Evangelista.