The Alkaline Paper Advocate

Volume 1, Number 2
Mar 1988


acid-free - In principle, papers are acid-free if they contain no free acid and have a pH value of 7.0 or greater. In practice, papermakers consider a paper having a pH value of 6.0 or greater to be acid-free. [1]

alkaline - Having a pH of 7.0 or greater.

alum - In the papermaking context, alumina sulfate: A12(SO4)3 ù 14H20, A12(SO4)3 ù 18H20, or a mixture of these hydrates. The increasing use of alum in papermaking since the 17th century (especially since the introduction of alum-rosin sizing in the mid-1800s, and the substitution of aluminum sulfate for the milder potassium aluminum sulfate about the same time, has been seen as the principal cause of deterioration of books since 1850. [1]

archival - Long-lived, or suited for use with records that will be retained indefinitely. It was formerly believed that archival paper had to be made of rag or cotton; now the term is almost synonymous with "permanent," in precise usage. It is often used vaguely and inconsistently to suggest that a product has certain keeping qualities.

buffering - In the context of alkaline papermaking, an acid absorber or alkaline reserve, almost always calcium carbonate.

calcium carbonate - CaCO3, one of the most stable, common, AND widely dispersed materials. It occurs in oyster shells, chalk, limestone, marble and travertine, and is a major cause of boiler scale when hard water is used in heating systems. It can be mined from natural surface deposits or precipitated (made synthetically) by reaction of calcium chloride and sodium carbonate in water solution, or by passing carbon dioxide through a suspension of hydrated lime (Ca(OH)2) in water. It is soluble in acids with evolution of carbon dioxide. [2]

durable - Wear-resistant; having high initial strength.

fine papers - Those used for printing, writing and cultural purposes.

freesheet - Paper made from purified wood pulp, containing no groundwood or unbleached pulp. Synonym: wood-free.

lignin - A polymeric material largely responsible for the strength of wood, and making up 16-34% of wood. Its nature is not fully understood, but it is considered to be a complex cross-linked, highly aromatic structure of high molecular weight which is readily oxidized. It is not a compound but a system, and its composition varies. It is more or less completely removed during chemical pulping, and further removed by bleaching. A spot test for detection of lignin or groundwood is described in Appendix F of "Fiber Analysis of Paper and Paperboard," T 401 om-82. Like the Barrow spot test for groundwood, it uses phloroglucinol, and cannot detect very small amounts.

permanent - Chemically stable; not prone to deterioration either from internal chemical reactions or from reactions with the environment.

pH - Measure of the hydrogen ion concentration and the degree of acidity or alkalinity on a scale ranging from 0 to 14 (not 1 to 14 as W. J. Barrow stated). Neutral point is 7.0, with values above 7 being alkaline. The letters "pH" stand for the French words for "hydrogen power." [3]


1. Matt T. Roberts and Don Etherington, Bookbinding and the Conservation of Books, A Dictionary of Descriptive Terminology. Washington, DC: Library of Congress, 1982.

2. The Condensed Chemical Dictionary. 10th ed., rev. by Gessner G. Hawley. New York: Van Nostrand Reinhold, 1981.

3. G. A. Smook, Handbook for Pulp & Paper Technologists. Atlanta: TAPPI, 1982.

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