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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.〔(Acid Free Paper and Archival Supply Sources ) Presbyterian Church (USA)〕 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). (ASTM's Paper Aging Research Program ). Retrieved November 4, 2007, (archive 2001-12-23 )/〕 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 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. Alkaline paper has a life expectancy of over 1,000 years for the best paper and 500 years for average grades.〔ASTM D 3290-00, "Standard Specification for Bond and Ledger Papers for Permanent Records", section 3.2.3.2 and Appendix X1〕 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 the machinery's useful life. The process is also significantly more environmentally friendly. Waste water and byproducts of the papermaking process can be recycled; energy can be saved in the drying and refining process; and alkaline paper can be more easily recycled.〔Lundeen, G.W. (1983) Preservation of paper based materials: Present and future research and developments in the paper industry. In K.L. Henderson and W.T. Henderson (eds) ''Conserving and preserving library materials (Papers presented at the Allerton Park Institute November 15–18, 1981)'': 73-88. Retrieved from http://hdl.handle.net/2142/459 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Acid-free paper」の詳細全文を読む スポンサード リンク
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