Mood changing nail polish is another fashion popular among young women based on the “mood stone” concept pioneered in the 1960s. Mood stones were placed in rings, necklaces, and bracelets changing color when the body was warm or cold as part of a thermochromic reaction. Mood changing nail polish is also based on a thermochromic reaction with the nails changing color with temperature. The nail polish is clear when the nails are warm, changing color when the nails cool. From a chemical standpoint, when the bond conjugation is interrupted, the polish is clear and when the bond conjugation is extended, the nail polish is colored.
Another introduction in color changing nail polish is photochromic nail polish, changing color when exposed to UV radiation, utilizing the same technology as photo-gray eyeglasses that automatically darken when outdoors. The UV radiation transforms the leuco form to the colored form allowing the nail polish to turn a pinkish purple.