Photobleaching—a Common Phenomenon

YELLOWING or darkening in sunlight is a common occurrence. Ultraviolet light with photon energies in excess of bond energies disrupts molecules and produces coloured and/or reactive groups. Wool yellowing increases below 365 mµ; at 254 mµ greening and free radicals occur1,2. Other materials form free radicals3. Skin reddens only below 320 mµ (ref. 4… CONTINUE READING