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Why is ultraviolet light especially harmful to paintings on paper?

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Ultraviolet (UV) light is particularly harmful to paintings on paper because it causes cumulative and irreversible damage to the artwork. Prolonged exposure to light, especially the UV component found in daylight, leads to the fading of colorants and the darkening of the paper support itself.1

This degradation is significant because it alters the artist's original intention by skewing intentional contrasts and causing a loss of depth and detail in the work. Because paper is an organic material, its response to environmental factors—including light—is critical to its preservation. To mitigate these risks, conservators emphasize that light damage is both cumulative and permanent, necessitating the use of UV filters on windows or framing materials, though these measures are not a complete solution and must be paired with prudent monitoring of light intensity and duration.1