Each November, a papermaker named Timothy Barrett gathers a group of friends and students on the grounds of the University of Iowa Research Park, a onetime tuberculosis sanitarium in Coralville, Iowa, for what he bills as a harvest event. Armed with hook-shaped knives, Barrett and his party hack away at a grove of bare, shrublike trees called kozo, a Japanese relative of the common mulberry. At his nearby studio, which is housed in the former sanitarium’s laundry facility, the bundles of cut kozo are steamed in a steel caldron to loosen the bark. After the bark is stripped from the kozo, it is hung on racks, where it shrivels to a crisp over a matter of days. Eventually the bark is rehydrated and sliced apart from its middle, “green” layer, and that layer, in turn, is sheared from the prized inner layer. It takes about a hundred pounds of harvested kozo trees to yield eight pounds of this “white bark,” from which Barrett will ultimately make a few hundred sheets of what connoisseurs consider to be some of the world’s most perfect paper.

Barrett, who is 61, has dedicated his life to unlocking the mysteries of paper, which he regards as both the elemental stuff of civilization and an endangered species in digital culture. For his range of paper-related activities, he received a $500,000 fellowship from the MacArthur Foundation in 2009. “Sometimes I worry about what a weird thing it is to be preoccupied with paper when there’s so much trouble in the world,” Barrett told me, “but then I think of how our whole culture is knitted together by paper, and it makes a kind of sense.” The Library of Congress and the Newberry Library in Chicago are among the institutions that often use his paper to mend their most important holdings, from illuminated manuscripts to musical scores penned by Mozart. In 1999, officials at the National Archives commissioned Barrett to fabricate paper on which to lay the fragile parchment originals of the U.S. Constitution, Bill of Rights and Declaration of Independence. A visitor to Washington, Barrett said, would be unlikely to notice his paper resting beneath the founding charters. “But if you kind of turn your head sideways and squint, you can see it.”

I first met Barrett last winter, when I went to his studio to see him make washi, the lustrous, translucent, tissue-thin Japanese-style paper that is the fruit of his mulberry harvest. Washi, he told me, was a centuries-old winter vocation of Japanese rice farmers. A thermostat on a cinder-block wall read 50.2 degrees, and Barrett was wearing a thick long-sleeve undershirt, a flannel shirt and a down vest beneath his heavy apron. He makes washi only six weeks each year, and forms sheets of paper only on Thursdays. Much of the rest of the time he is preparing the white bark according to a regimen that includes cooking it in a solution of wood-ash lye, laboriously picking the strands free of tiny bits of debris, beating them with a mechanical stamping device, pounding them with mallets and then macerating the stringy clumps in a tub outfitted with S-shaped blades that he says are modeled on a medieval Japanese sword.

He stepped inside an 8-by-10-foot corner of the studio that was enclosed by curtains of plastic sheeting and scooped a few liters of wet white bark fibers into a vat of purified water. Then he poured in what he called a “formation agent” — plant secretions that, he said, were the key to the amazing strength, softness and flexibility of sheets no thicker than a Kleenex. He stirred the vat with a four-foot pole, then pushed and pulled the prongs of a huge, rakelike wooden tool through the solution to disperse the fibers evenly in the water. “A hundred and fifty strokes,” he said, though he didn’t appear to be counting. He stirred with the pole again and paused. Now he was ready to make a sheet of paper.