How does fluorescence work? It’s all about energy! When light shines on a fluorescent pigment, a photon of light is absorbed by the molecule. In effect, energy is absorbed. This excites the electrons inside the molecule. As the excited electrons loses energy. the electrons emit the absorbed photon of light, which we see as fluorescence. Daylight fluorescent pigments were invented in the 1930’s by the Switzer brothers under the name Day-Glo. Fluorescent pigments are solid dye solutions in resin carriers. Fluorescent dyes in their undissolved state do not fluoresce. Once these dyes are dissolved in a carrier resin and are ground into a fine powder, they become fluorescent pigments.
Luminescent pigment was discovered in 1936 when radioactive Radium was used to create phosphorescent material! When you shine light on a glow-in-the-dark object, the incoming photons (packets of light) excite the phosphor molecules. These molecules release the energy they have stored by giving out photons, creating a glow. Phosphors are a chemical that absorbs energy and re-emits it as visible light. Zinc sulphide and strontium aluminate are the two most commonly used phosphors because they re-emit energy over a long period.
Iridescents are familiar for their metallic lustre where they replicate the look of polished metals. These colours are derived from mica plateletes which are coated with an extremely thin layer of an inorganic pigment. Iridescent pearls and silvers are mica plateletes coated with titanium dioxide. Iridescent golds and coppers have an iron oxide coating. The plate-like shape allows the pigments to be easily oriented into parallel layers. When viewed, a portion of light will be reflected by the uppermost layer of pigments, while the remainder of the light will be transmitted and subsequently reflected by lower layers. It is this multiple reflection of light from many microscopic layers that produces the shimmer.
Welcome to colour made by physics and imagine a blue that changes colour when viewed from different angles! Interference pigments consist of titanium dioxide attached to various layers of mica. Light striking the surface is refracted, reflected and scattered by the layers that make up the pigment. The colour effect we see is angle dependent. At very oblique angles over a pale colour, the compliment of the main interference colour can be seen, so that interference red can appear green. Looking at the outside square, keep moving around this panel to see how the colour seems to shift.