It is universally accepted that ultraviolet wavelengths are the most damaging photochemically to organic materials. However, few curators seem to recognize that visible light is only somewhat less damaging. An explanation of what happens seems to be in order. The color of the material is of extreme importance. If white light strikes a red object, the red wavelengths are reflected and do little damage, but violet, blue and green in some percentages are more or less totally absorbed, causing photochemical reactions in the pigments. Likewise, if the objects is blue or violet, wavelengths in red, yellow, green, are almost totally absorbed and damage follows. All light is converted into heat when absorbed. Heat breaks down the long chain molecules in fabrics. Perhaps the worst effect is on black material, which absorbs most of the entire spectrum, thus affecting both dyes and long chain molecules. White materials are perhaps least affected by light but will turn yellowish and the fibers become embrittled by heat as infrared is absorbed by the container, such as a trunk in an attic.