What is "phototendering"

Phototendering is the process by which organic fibres and textiles lose strength and flexibility as a result of exposure to sunlight. It is the ultraviolet component of the sun's spectrum which affects fibres, causing chain degradation and hence loss of strength. The rate of deterioration is also affected by pigments and dyes present in the textiles. Pigments themselves can also be affected, generally fading after exposure. Great care is needed to preserve museum artefacts from the harmful effects of UV light, which can also be present in fluorescent lamps. Many synthetic polymers are also degraded by UV light, and UV stabilisers are added to many thermoplastics.