Polymethyl methacrylate (PMMA), acrylic, sheet with fluorescent tint. Reducing the amount of pigment or dye to below the saturation point results in tinted colour. Fluorescent pigments glow brightly because they absorb light in the ultraviolet portion of the spectrum and emit light in the visible portion. Therefore, tinted materials will appear brighter than their surroundings because they emit more visible light. The cut edges appear more saturated than the faces, due to a phenomenon known as edge glow, or lit edge. It is caused by lightwaves being refracted internally and transmitted out through the edge, rather than the surface. The effect is enhanced by fluorescent pigment.