Sunbleaching

Sunbleaching is the light-induced fading or lightening of color in materials caused by exposure to sunlight. It occurs primarily through ultraviolet (UV) radiation, which breaks chemical bonds in pigments and dyes and initiates photochemical reactions that degrade color. Heat and moisture can accelerate these reactions, and oxygen can participate in oxidative processes that accompany photodegradation.

Materials commonly affected include textiles, paper, plastics, and painted surfaces. In fabrics, sunbleaching often yields uneven fading on exposed areas, with some colors fading more rapidly than others depending on dye chemistry and fiber type. Natural dyes such as indigo or madder are typically more susceptible to fading, while synthetic dyes vary in lightfastness. Paper and artwork may lose contrast or yellow as inks, coatings, and binders degrade. Outdoor painted surfaces can lighten over time, and plastics or wood exposed to sun may experience embrittlement, cracking, or surface crazing.

Mitigation and care strategies focus on limiting sun exposure and using protective measures. Approaches include shading or removing items from direct sunlight, applying UV-filtering coatings or coatings with lightfast pigments, and choosing durable, fade-resistant materials. In archival and museum contexts, sun exposure is minimized to preserve artifacts, while storage and display systems may employ UV-stabilized glass, controlled lighting, and timed exposure.