Did You Know: Rag Paper vs Wood Pulp Paper
Excerpted from http://www.cycleback.com/printsexamination/sixteen.html
Rag versus wood pulp.In the early history paper was made from rags.Starting about the mid 1800s, rag pulp began to be replaced by wood pulp.Wood became a popular choice due to the scarcity of rags and because wood pulp paper was cheaper to manufacture.The first successfully made American wood pulp paper was manufactured in Buffalo, New York, in 1855. By 1860, a large percentage of the total paper produced in the U.S. was still rag paper. Most of the newspapers printed in the U.S. during the Civil War period survived because they were essentially acid-free 100% rag paper, but the newspapers printed in the late 1880s turn brown because of the high acid content of the wood pulp paper. In 1882, the sulfite wood pulp process, that is still in use today, was developed on a commercial scale and most of the high acid content paper was used thereafter in newspapers, magazines and books.
Counterintuitively, modern paper, especially in books, letters and newspapers, is much more likely to turn brown and brittle than paper from before the American Civil War. For the beginning collector, the paper on an early 1800s print can be surprisingly fresh and white.