acid-free paper

In principle, papers that 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 Also referred to as acid-neutral. Note: 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. Acid-free paper may become acidic through contact with acidic material or atmospheric pollutants.