thumb|the acid-free-paper symbol. acid-free paper is paper that if infused in water yields a neutral or basic ph (7 or slightly greater). it can be made from any cellulose fiber as long as the active acid pulp is eliminated during processing. it is also lignin- and sulfur-free.http://www.history.pcusa.org/cong/acidpaper.html acid-free paper addresses the problem of preserving documents and artwork for long periods. == overview == paper made from wood-based pulp that has not had its lignin removed turns yellow, becomes brittle, and deteriorates over time.teygeler, r. (2004). preserving paper: recent advances. in j. feather. (ed.), managing preservation for libraries and archives: current practice and future development. 90. burlington: ashgate. isbn 0-7546-0705-4 when exposed to light and/or heat, the molecules in the acidic paper will break down even faster.arnold, b.r. (2002). astmâs paper aging research program. retrieved november 4, 2007, from http://palimpsest.stanford.edu/byauth/arnold/astm-aging-research/ acidic wood-pulp paper became commonplace in the late 19th century, and in the 1930s william barrow (a chemist and librarian) published a report about the deterioration of acidic paper in the libraries.cedzova, m. et al. (2006). patents for paper deacidification. restaurator: international journal for the preservation of library and archival material, 27, 35. for fear of the gradual disintegration of written materials, measures have since 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 acids 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. in order for paper to last at least 100 years it must have an alkaline reserve of 2% or more.teygeler, r. (2004). preserving paper: recent advances. in j. feather. (ed.), managing preservation for libraries and archives: current practice and future development. 89. burlington: ashgate. isbn 0-7546-0705-4 today, much of the commercially produced paper is acid-free,dahlo, r. (2000). the rationale of permanent paper. in w. manning & v. kremp (eds.), ifla publications 91: a reader in preservation and conservation. 59. munchen: k. g. saur. isbn 3-598-21817-6. but this is largely the result of a shift from [[ch
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