Research on Paper Though Time by a University of Iowa team led by Timothy Barrett, director of papermaking facilities at the UI Center for the Book, showed that the earliest paper tended to be the most durable over time because of high qualities of gelatin and calcium in its manufacture. Over three years the team analyzed 1,578 historical papers made between the 14th and the 19th centuries. Barrett and his colleagues devised methods to determine their chemical composition without requiring a sample to be destroyed in the process, which had limited past research.
“This is news to many of us in the fields of papermaking history and rare book and art conservation,” says Barrett. “The research results will impact the manufacture of modern paper intended for archival applications, and the care and conservation of historical works on paper.”
Barrett says one possible explanation for the higher quality of the paper in the older samples is that papermakers at the time were attempting to compete with parchment, a tough enduring material normally made from animal skins. In doing so, they made their papers thick and white and dipped the finished sheets into a dilute warm gelatin solution to toughen it.
“Calcium compounds were used in making parchment, and they were also used in making paper,” Barrett says. “Turns out they helped prevent the paper from becoming acidic, adding a lot to its longevity.”