Acid-free paper Acid-free paper 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 addresses the problem of preserving documents and artwork for long periods. Paper made from wood-based pulp that has not had its lignin removed turns yellow, becomes brittle, and deteriorates over time. When exposed to light and/or heat, the molecules in the acidic paper will break down even faster. Acidic wood-pulp paper became
Alkali–silica reaction mineral acid-base reaction between NaOH or KOH, calcium hydroxide, also known as Portlandite, or (Ca(OH)), and silicic acid (HSiO, or Si(OH)). When complete and to simplify, this reaction can be schematically represented as following: However, the ASR reaction significantly differs from the pozzolanic reaction by the fact that it is catalysed by soluble alkali hydroxides (NaOH / KOH) at very high pH. It can be represented as follows using the classical geochemical notation for fully hydrated dissolved silica (Si(OH) or silicic acid: HSiO), but an older industrial notation also exists (HSiO, hemihydrated silica (does not exist), by analogy with carbonic