Acid-free paper

Paper made from wood-based pulp that has not had its lignin removed turns yellow, becomes brittle and deteriorates.

William Barrow (a chemist and librarian) published a report about the deterioration of acidic paper in the libraries.

[6] Much commercially produced paper is acid-free but this is largely the result of a shift from kaolin clay to precipitated calcium carbonate (PCC) as the main filler material in the pulp.

[8] The making of alkaline paper has several other advantages in addition to the preservation benefits afforded to the publications and documents printed on it.

Because there are fewer corrosive chemicals used in making alkaline paper, the process is much easier on the machinery, reducing downtime and maintenance and extending machines' useful life.

[5] 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.

The objective of ANSI Z39.48-1992 "is to establish criteria for coated and uncoated paper to last several hundred years" under optimal conditions in libraries and archives.

[13] Manufacturers of acid-free paper can indicate the compliance of their product with the test requirements of the ISO 9706 or ANSI Z39.48-1992 standards using a circled infinity symbol (Unicode code point 267E, ♾).