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Question:

    Why does ultraviolet light cause color to fade?

Answer:    

    Because of photodegradation.

It is all about the chemical makeup of an object. The technical term for color fading is photodegradation. There are light absorbing color bodies called chromophores that are present in dyes. The color(s) we see are based upon these chemical bonds and the amount of light that is absorbed in a particular wavelength.

Ultraviolet rays can break down the chemical bonds and thus fade the color(s) in an object - it is a bleaching effect. Some objects may be more prone to fading, such as dyed textiles and watercolors. Other objects may reflect the light more, which makes them less prone to fade.

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Library of Congress Web SiteFurther Reading
  • Nassau, Kurt. The Physics and chemistry of color: the fifteen causes of color. New York: Wiley, 2001. 481 p. .

SearchFor more print resources...
Search on "Color," "Dyes and dyeing chemistry," or "Light" in the Library of Congress Online Catalog.

Drawing of the sun shining down on a faded green shirt.

Image: see caption below
What is ultraviolet light? From "Ultraviolet: the Science Behind the Medicine." ClarionHEALTH, c2000.


Of the three types of energy contained in sunlight--ultraviolet radiation, visible light, and infrared radiation--ultraviolet (UV) can be the most dangerous. From "Cool in the Shade," Texas A&M University.

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 July 31, 2017
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