Our sun emits an electromagnetic spectrum of radiation—much of which is harmful to life on our planet. Thankfully, the earth’s magnetic field deflects many of these rays, while others are adsorbed by our atmosphere. Table 1 shows wavelengths of light reaching our atmosphere, although the most harmful—UV-C and some portion of UV-B radiation is filtered out by the ozone layer. The energy of these rays is inversely proportional to the wavelength. Much is made of the more energetic nature of UV radiation, but approximately 10 times more visible radiation reaches the earth’s surface. Some sun-related effects are thought attributable to this component. Any scientific study into the effects of sun on hair necessitates a reproducible means of sun exposure. External weathering is complicated by variation in the sun’s intensity with the seasons together with other weather-related variables, such as cloud cover, rain, variable humidity, etc. Therefore, attention turns to artificial means of achieving this goal and the availability of accelerated weathering devices.