Lignin-Free

Lignin-Free

Definition: Lignin-Free refers to paper, mat board, or other materials that have undergone chemical processing to remove lignin, a natural component of wood pulp. Since lignin breaks down over time and releases acids that cause yellowing, brittleness, and deterioration, lignin-free products are preferred in archival framing and conservation to ensure long-term stability of artwork and documents.

Importance in Conservation

• Archival Standards: Lignin-free materials are a cornerstone of conservation-grade framing, preventing acid migration into valuable artwork.
• Longevity: By removing lignin, paper and boards resist yellowing and embrittlement, extending their usable life for centuries when stored properly.
• Compatibility: Lignin-free boards are often also acid-free and buffered with an alkaline reserve for added protection.

Applications

• Matting: Lignin-free mats are essential for museum-quality framing.
• Backing Boards: Used behind artworks to prevent deterioration caused by lignin migration.
• Archival Storage: Boxes, folders, and sleeves made from lignin-free materials protect photographs, manuscripts, and prints.

How Lignin is Removed

• Chemical Pulping: Processes such as the kraft or sulfite pulping method chemically remove lignin from wood pulp.
• Bleaching: Lignin traces are further eliminated or neutralized to improve purity and permanence.
• Alpha Cellulose Boards: Many conservation products are manufactured from purified alpha cellulose, which is naturally lignin-free.

Preventive Conservation

• Choose lignin-free and acid-free mat boards for all valuable works on paper.
• Replace any wood-pulp, lignin-containing boards that may be in older frames.
• Avoid direct contact of artwork with cheap cardboard or kraft paper, which contain high levels of lignin.

Related Terms

• Acid Free
• Acid
• Entropy
• Acid Outgassing