acid-free paper
In principle, papers which 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. Such
papers may be produced from cotton fibers, rags,
esparto, jute, chemical wood pulps, or virtually
any other fiber, with special precautions being
taken during manufacture to eliminate any active
acid that might be present in the paper pulp.
However free of acid the paper may be immediately
after manufacture, the presence of residual
chlorine from bleaching operations, aluminum
sulfate (alum) from sizing, or sulfur dioxide in
the atmosphere, may lead to the formation of
hydrochloric or sulfuric acid unless the paper has
been buffered with a substance capable of
neutralizing acids. See also: ALKALINE RESERVE .
(144 , 198 )
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