| Acid-free Paper |
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| CATEGORIES ABOUT ACID-FREE PAPER | |
| writing paper | |
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Acid-free paper is Paper that has a neutral or Basic PH (7 or slightly greater). It addresses the problem of Preserving documents for long periods. Paper made from wood-based pulp that has not had its Lignin removed goes Yellow and deteriorates over time. When exposed to light and/or heat, the molecules in the wood-pulp (or acidic) paper will break down even faster. It was only in the 1930s that the effects of Wood-pulp Paper became known, when William Barrow (a librarian) published a report about the deterioration of acidic paper in our libraries. For fear of the gradual disintegration of written materials, measures have been taken to improve the quality of paper. During production, acid-free paper may be treated with a mild base (usually calcium or magnesium Bicarbonate ) to neutralize the natural Acid s occurring in Wood Pulp , and it may also be Buffered to prevent the formation of additional acids (as may develop from the application of Sizing ). The bicarbonate is added in excess, to supply the paper with an alkaline reserve to provide protection from further attack by acids remaining in the paper or supplied by the environment (e.g. atmospheric Sulfur Dioxide ). The bicarbonate during drying loses carbon dioxide and water and is converted to Calcium Carbonate or Magnesium Carbonate . Paper intended to last for very long periods (e.g. 500 years) should contain approximately 3 weight percent of the carbonate. Today, most commercially produced paper is acid-free, but this is largely the result of a shift from china clay to (cheaper) chalk as the main filler material in the pulp: chalk reacts with acids, and therefore requires the pulp to be chemically neutral or alkaline. The Sizing additives mixed into the pulp and/or applied to the surface of the paper must also be acid-free. There are various standards for "acid-free" paper, with differing requirements. In some quarters, paper having a pH between 6 and 7 is often also considered acid-free. Acid-free (alkaline) paper that additionally is ''uncoated'' and meets certain ''standards for folding and tearing'' is authorised by the American National Standards Institute ( ANSI ) to carry the following notice: "The paper used in this publication meets the minimum requirements of the American National Standards Institute for Information Sciences—Permanence of Paper for Printed Library Materials, ANSI Z39.48-1992." The objective of ANSI Z39.48-1992 NISO Standards "is to establish criteria for coated and uncoated paper to last several hundred years" under optimal conditions in libraries in archives. The desired outcome of the standard is to reduce future preservation problems. The scope of the standard is to cover publications and documents bought and maintained by libraries and archives. Such works include scholarly journals, periodicals, monographs, government documents, original documents, and significant works in fiction and non-fiction. The sign of ANSI approved alkaline paper is the ''circled infinity symbol''.The Chicago Manual of Style Online §1.35; www.chicagomanualofstyle.org/ch01/ch01_sec035.html Archival paper is an especially permanent, durable acid-free paper. Archival paper is meant to be used for publications of high legal, historical, or significant value. In the USA, such paper must also be approved by the ANSI standards. {Link without Title} The international standard for "permanent" paper is ISO 9706. REFERENCES EXTERNAL LINKS |
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