The Sun's Spectrum
Radiation from the sun is composed of ultraviolet, visible, and infrared light. These bands of radiation are best defined by their wavelengths measured in nanometers. One nanometer equals one billionth of a meter in length.
Ultraviolet radiation, the sun's most damaging rays, falls in the 295 to 400-nanometer range and accounts for some 7 percent of the sun's total intensity. Visible radiation falls between 400 and 800 nanometers and makes up about 55 percent of the sun's total intensity. Infrared radiation measures from 800 to about 2450nm and comprises about 38 percent of the sun's total intensity.
The Causes of Fading and Degradation
Visible light causes some fading and material degradation. But we cannot block visible light and maintain bright interiors and the ability to view our diecasts. More damage can occur from exposure to the sun's infrared radiation.
Synthesized materials such as plastic, paper and dyes are especially susceptible to UV damage. And these materials are everywhere: in furniture, carpeting, plastic flooring, wood stain, wallpaper, pictures and posters. Standard window glass blocks UV radiation in sunlight below 310 nanometers in wavelength, which provides protection against the highest-energy damaging radiation.
Still, longer wavelength UV radiation is harmful. Damage occurs when carbon-based chemicals in these materials undergo destructive chemical reactions assisted by photo-initiators that can be present in manufactured synthetics. These photo-initiating chemicals are activated by UV light and cause bond-breaking reactions in nearby organic molecules.