In the late 1950s it was recognized that the longevity of paper is a function of its acidity or alkalinity: the lower the acidity and higher the alkalinity, the greater the longevity of paper. At about that time Hercules Incorporated
developed the first alkaline sizing that made acid-free paper possible.
"Despite the advances in paper making and the identification of and concern around the brittle book problem, it took decades before the adoption of ANSI NISO
Standard Z39.48-1984 - Permanence of Paper for Publications and Documents in Libraries
in 1984. This voluntary standard covered pH value, tear resistance, alkaline reserve, and lignin thresholds for paper to last thousands of years and was developed to encourage the use of acid-free paper in library materials.
The development of the initial standard was a result of the work of the Council on Library Resources, which effectively lobbied ANSI to adopt the guidelines.
In 1986, Standards Committee II of NISO
was established to expand Z39.48-1984 to develop standards for coated paper
, and was again called upon in 1988 to review and revise the standards for uncoated paper" (Wikipedia article on Acid-free paper, accessed 9-2020).