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Why is wood-pulp paper less suitable for preserving artwork?

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Watercolor painting by Berthe Morisot showing Edma seated on a sofa in a floral dress with her young daughter Jeanne beside her, both facing slightly right. — Drawing *The Artist's Sister, Edma, with Her Daughter, Jeanne*, watercolor over graphite on paper by Berthe Morisot, 1872; in the collection of the National Gallery of Art, Washington, D.C.

Wood-pulp paper is considered less suitable for preserving artwork because it often contains "inherent vice," a term used by conservators to describe materials that are chemically unstable and prone to inevitable deterioration.1

The primary issue with wood-pulp paper is its chemical composition. Unlike high-quality, acid-free papers—which are preferably made from 100 percent rag content—wood-pulp paper often retains lignin, a complex organic polymer found in wood cell walls. Over time, the presence of such components and the acidic nature of lower-quality paper lead to significant degradation, including:12

Discoloration and Acidity: The paper darkens and becomes brittle due to chemical deterioration.1
Image Degradation: Acidic components can cause "matte-burn" and chemical transfer, which negatively impact the artwork's appearance.1
Increased Vulnerability: The absorbent nature of paper makes it susceptible to environmental factors, and acidic materials can accelerate the damage caused by light exposure and chemical reactions.13

To ensure the longevity of drawing media, museum standards prioritize the use of acid-free, archival-quality supports to prevent these destructive processes.13