Lignin

Lignin

Definition: Lignin is a naturally occurring complex polymer found in the cellular structure of wood and plant material. It acts as a binding agent that gives rigidity and strength to cell walls, helping wood fibers hold together. In the context of paper and framing, lignin becomes a concern because, as it deteriorates, it releases acids that accelerate the breakdown of paper fibers, causing brittleness, discoloration, and long-term damage to artwork and mats.

Role in Materials

• Structural Function: Provides stiffness and hardness to wood, making it essential for the tree's mechanical strength.
• Presence in Paper: Found in wood-pulp paper products, especially non-archival or lower-quality papers.
• Conservation Concern: Lignin-containing papers, mats, and boards are inherently acidic and prone to yellowing and embrittlement over time.

Deterioration Effects

• Acid Release: As lignin breaks down, it produces acids that migrate into surrounding materials.
• Yellowing: One of the most common visible results of lignin deterioration, giving paper a brown or yellow cast.
• Brittleness: Paper and board lose flexibility as acid hydrolysis weakens cellulose fibers.
• Off-Gassing: Volatile compounds released from lignin can harm nearby artworks and mount boards.

Preventive Measures

• Use lignin-free, acid-free mat boards and backings for conservation framing.
• Select cotton rag boards or alpha-cellulose boards that are chemically purified and buffered.
• Avoid storing valuable artwork in direct contact with wood or cheap paper products.
• Regularly inspect framed works for early signs of yellowing or acid burn.

Treatment

• Deacidification: Conservators may treat paper with an alkaline buffer spray or bath to neutralize acids and slow deterioration.
• Re-matting: Replace lignin-containing mats or backings with archival-grade materials.
• Encapsulation: Use archival polyester film (such as Mylar) to physically isolate acidic materials from artwork.

Related Terms

• Acid
• Off Gassing
• Yellowing
• Acid Burn