This is the Year of Glass. From Wausau and Newark, N.J., to Sacramento, Calif., and Kalamazoo, Mich., scores of museums are honoring the 50th anniversary of studio glass, a transcendent art form that is powerfully malleable, notoriously fragile and stunningly young. And it was born here. “You have to remember that when Harvey Littleton started this in 1962, there were no art galleries carrying glass. There were no collectors buying glass. That world has exploded,” said Michael Monroe, guest curator for Madison’s upcoming tribute to the studio glass movement titled “Spark and Flame: 50 Years of Art Glass and the UW-Madison,” which opens April 21 at the Chazen Museum of Art.