Materials with so-called structural color don’t use pigments to create pink, green, or blue—or in the case of this piece of chocolate, all the colors of the rainbow. The principle behind many structural colors is a series of micrometer-size surface features that are small enough to interact with and amplify specific wavelengths of light, thus creating various colors. Samy Kamkar, a security researcher who took on this project in his spare time, figured he could make tiny surface features on chocolate by molding the melted candy onto a 500 line/mm diffraction grating under vacuum.
After the chocolate cooled, the diffraction grating had transferred all those lines, which are each about 2 µm wide, to the surface of the chocolate and produced this colorful result. He notes that it doesn’t feel any different on his tongue compared with non-textured chocolate and that tempering the chocolate may help the microtexture last longer.
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