“The deeper the blue becomes, the more strongly it calls man towards the infinite, awakening in him a desire for the pure and, finally, for the supernatural… The brighter it becomes, the more it loses its sound, until it turns into silent stillness and becomes white.”
Wassily Kandinsky

Last week I witnessed two young girls infront of the local drugstore’s nail polish rack. They were cautiously discussing the ‘magic’ behind new nail polishes that change color with different temperature. Neither of them really knew how it worked and it made me a little contemplative. Is astonishment a product of inconceivability or enlightenment over the unknown? Are you a person that prefers the answer or do you like to keep things mysterious to yourself? There is a great chance you have already come across at least one object that amazes with colour-changing properties (e.g. ‘mood rings’, optical glasses that darken in the sun, fun mugs that reveal hidden messages when hot water poured in etc.) and for those of you who want to know the basic science of common color-changing products I try to explain it easily:

The trick behind the girls’ beautiful color-changing nail polishes is the use of thermochromic dyes. Chromism is described by a process that induces a (sometimes reversible) change in the colors of compounds. Thermochromatic dyes react to the temperature they are exposed to and can be based on either Leuco dyes (see example here), where molecules can acquire two forms, a colorless and colorful one, and Thermochromatic liquid crystals. Here the color-change comes from the molecules’ ability to leave different spaces between their alignment and layers. With different sizes of the ‘voids’ the light passing through the crystals is perceived as a different spectral color. Same changes of ‘arrangement’ in your dye can be achieved by photo exposure (photochromism, e.g. the uv-tinted optical glasses). A very different but exciting way to achieve a change of color is by the help of solvent polarity (solvatochromism). This will make your nail polish change colors with the contact of something polar, like water. I can get all excited with the aesthetic uses of molecular switches, there are already highly interesting approaches to use them in future (check here, here, here and here). Having a molecular switch manicure, Ea Birkkam

today: monochromatic seasonal transition