Energy distribution of sunlight Visible, 44% Ultra-violet, 5% Infra-red, 51% VIS: 380-780mm Visible light PAR: 400-700mm Photosynthesis active radiation UV Visible 380-780nm 780-2500nm >2500nm Solar Infra-red Heat radiation A Resene CoolColour™ uses pigments that reflect more of the sun’s energy than normal pigments. Energy distribution of sunlight Visible, 44% Ultra-violet, 5% Infra-red, 51% VIS: 380-780mm Visible light PAR: 400-700mm Photosynthesis active radiation UV Visible 380-780nm 780-2500nm >2500nm Solar Infra-red Heat radiation A Resene CoolColour™ uses pigments that reflect more of the sun’s energy than normal pigments. Sunlight energy is made up of 44% visible light, 5% ultra-violet light and 51% infra-red light. Traditionally light reflectance values have been used to define what colours are suitable for heat prone substrates, however visible light reflectance values only measure a proportion of the light and ignore the effects of ultra-violet and infra-red light. Total Solar Reflectance (TSR) values take into account all three forms of light to give a better measure of the reflectance of the colour. A Resene CoolColour uses pigments that reflect more of the sun’s energy resulting in the same visible light reflectance value as the standard colour but a considerably higher Total Solar Reflectance value. The solar spectrum includes infra-red radiation that Resene CoolColour pigments are designed to reflect. Replacing the standard black pigment that absorbs all infra-red with a Resene CoolColour black pigment reduces the heat absorption. Some blues, greens and reds are transparent to infra-red radiation so are best used with Resene Quick Dry or Resene Galvo-Prime to reflect infra-red that passes through these hues. In terms of technology, the Resene CoolColour effect can also be seen in plants. Most plants have leaves of a very high chroma green. If those leaves reached the same temperature when exposed to solar radiation as those of a similarly coloured paint they would shrivel and die. The fact they don’t is because that pigment – chlorophyll – absorbs what it needs from the visible range to photosynthesise but reflects the infra-red range, keeping the plant cool. | 69