Why Paper Deteriorates: Understanding Its Environment and Aging

Paper is a hygroscopic, cellulosic material whose long-term stability depends strongly on both its composition and storage environment. Over time, chemical, physical, and biological processes can lead to discoloration, embrittlement, deformation, loss of mechanical strength, and microbial damage.

For historic paper collections, acidity has been an important cause of deterioration. 

Many papers produced during the 19^th and 20^th centuries contain acidic components from papermaking processes such as alum–rosin sizing. These acids promote acid-catalyzed hydrolysis of cellulose, reducing the degree of polymerization and causing the familiar yellowing and brittle texture of aged paper. Modern papers are generally produced under neutral or alkaline conditions, so this type of inherent acid degradation is much less common in newly manufactured paper.

Humidity is one of the most important environmental factors affecting the condition of paper. Cellulose continuously absorbs and releases moisture from the surrounding air. High or fluctuating humidity causes repeated swelling and shrinkage of fibers, which may result in cockling and dimensional instability. Elevated moisture also increases the rate of chemical degradation and creates favorable conditions for microbial activity. 

Temperature also plays a major role in the aging process. Higher temperature accelerates chemical reactions associated with cellulose degradation, including hydrolysis and oxidation. Cooler and stable storage conditions therefore generally slow paper aging. Temperature and humidity should be considered together, particularly in warm and humid climates where both factors can accelerate deterioration.

Light and atmospheric pollutants can further contribute to aging. Exposure to light, particularly UV radiation, may induce photo-oxidative reactions affecting cellulose, lignin, pigments, dyes, and inks. Depending on the material, this may appear as fading, yellowing, or gradual loss of mechanical properties.

Mold is another major concern for paper-based collections, particularly under conditions of elevated humidity and limited air circulation. Fungal growth can produce staining, unpleasant odors, and enzymatic degradation of cellulose and other organic components. Once established, mold damage can be difficult to reverse, making preventive conservation particularly important.

Paper deterioration is therefore the result of interacting factors rather than a single mechanism. Material composition, moisture, temperature, light, pollutants, microorganisms, and time all influence the lifetime of paper-based collections

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An awareness of these often unavoidable factors has led NEXTBOND to develop PaperCura, a cellulose-based coating designed to protect paper. The solution improves resistance to moisture and biological deterioration while preserving the original appearance of paper. PaperCura creates a thin protective layer on the paper surface with minimal intervention and can be applied by either spray or immersion.