Acid-free paper durable acid-free paper. Archival paper is meant to be used for publications of high legal, historical, or significant value. In the USA, such paper must also be approved in accordance with the ANSI standards. The international standard for "permanent" paper is ISO 9706 and for "archival" paper, the standard is ISO 11108. Often, cotton rag paper is used for archival purposes, as it is not made from wood-based pulp. Thus, "archival paper" is sometimes broken down into two categories: Acid-free paper Acid-free paper is paper that if infused in water yields a neutral or basic pH (7 or slightly greater).
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.