Acidfree

Acidfree refers to materials manufactured without free acids, typically with a pH at or above 7 at the time of production. In archival and art contexts, acid-free is often paired with lignin-free and buffered, indicating additional measures to resist deterioration. Lignin, a component of wood pulp, can form acids as it degrades, leading to yellowing and embrittlement. Buffered acid-free papers include alkaline substances such as calcium carbonate that slow acid migration from the environment and improve longevity.

Common applications include archival storage of documents and photographs, art papers, scrapbooks, envelopes, and storage boxes. Not all products labeled acid-free meet archival standards; some are simply pH-neutral or free of visible acids. For higher longevity, materials should be acid-free, lignin-free, and buffered, and many professionals look for certifications or standards such as ISO 9706, which specify permanence and aging resistance for paper.

Practical guidance: verify labeling for pH, lignin content, and buffering; store important items in acid-free enclosures in a cool, dry, and dark environment; keep away from acidic materials such as newsprint or certain glues and metals that can contribute to acid migration. In short, acid-free denotes reduced acidity at manufacture, but archival-grade permanence often requires additional properties and verification.