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
Casein paint or varnished for a gloss finish. The binder for casein paint is made by dissolving casein in an alkali, usually lime, ammonium carbonate, or borax. Casein itself is precipitated from milk by the action of an acid or the enzyme rennet. Lime casein works well on porous surfaces, even outdoors, though it has a short shelf-life and must be used with pigments that are balanced against the binder's low pH. Ammonium carbonate casein has similar strengths and weaknesses. Borax casein has a shelf-life of several weeks, is pH neutral, and can be used outdoors through the addition of linseed oil.