Thermochromic mug changing colour. As the sides of the mug heat up due to the hot drink it contains, the dark dye becomes transparent, revealing the picture of a cat beneath. The dark layer contains a leuco dye. Leuco dyes are molecules that can take two forms, one of which is coloured and the other colourless. The transition occurs at a certain temperature, determined by the structure of the molecule.
Model release not required. Property release not required.