Many important documents need to be preserved for extended periods of time. Conventional paper products will slowly degrade, thanks to the high level of acid which normally exists in paper. Archival paper is made slightly alkaline or with a neutral pH so that it will not yellow and turn brittle with age. Most paper companies offer such papers in their line for archivists, governments, libraries, and artists. However, it is important to remember that this type of paper is only useful under the right conditions.
Two primary factors contribute to the degradation of conventional paper. The first is lignin, a component of the cell walls in plants. Lignin will turn yellow as it is exposed to heat, causing yellowing paper. Acid makes the paper more fragile, thin, and brittle. Newspapers provide perhaps the best example of the antithesis of archival paper, since they are made as cheaply as possible, as most people recycle them after one reading. Newspapers quickly turn yellow and brittle, an undesired trait in important documents.
Historically, important documents have been printed on vellum, a material made from calfskin. With a wider adoption of paper, people started noticing that their paper documents were not as durable as those printed on vellum. The discoveries of acid and lignin led to the development of archival paper.
The process for making this paper is more complex, resulting in a more expensive end product. The paper is thoroughly treated to remove lignin, and then is made pH neutral, or preferably alkaline, with the addition of soda ash or calcium carbonate. Alkaline paper will be better able to resist the acidic environment than neutral paper. The resulting product holds ink and colors well, and will last far longer than conventional paper.
However, archival paper prefers alkaline conditions. Many companies sell archival tissue sheets which can be laid between sheets of archival paper, and alkaline storage boxes for the paper. The paper should be stored in a cool, dry, dark place to extend its life even further. Most document repositories have humidity control measures in place to ensure that their paper is kept in the best conditions.
In addition to important documents, archival paper is also used by artists so that their work will be preserved. Scrapbookers may also use it in archival scrapbooks, and important editions of books are printed on this type of paper so that they will last. Most paper supply stores offer a selection of archival papers, which are sometimes designated as “lignin free” or “pH neutral.”