ocr: a (hes - Vhyteof - - - The profile and water- mark initials of Luigi Mecella leave no doubt: This sun-goldened sheet, molded in the renowned papermaking center of Fabriano, Italy, is his handiwork. Endlessly useful and often elegant, versatile paper can be at vehicle. for a writer's expression, a surface, for an artist's brush, and, sometimes, art itself By JON R. LUOMA Photographs by SISSE BRIMBERG NATIONAL GEOGRAPHIC PHOTOGRAPHER 88