Over the past decades, there have been vigorous efforts to create heat resistant pigments in the ceramics industry, as most tints break down at the very high temperatures under which ceramics are fired. Novel ways were discovered of doping refractory metal oxides of titanium, zirconium, chromium, and so on, with other metal ions to produce a wide selection of high temperature colours. The behaviour of these mixed oxides were examined under infra-red and the results showed an ability to withstand a range of very high temperatures. Focusing on this aspect, further refinements were made to maximise this for use in various commercial applications. Using these findings Resene took the very popular roofing colour Karaka and incorporated into it these new infra-red reflecting pigments. Comparing the new blend against traditional coatings over a five minute standard Resene test revealed a 12°C drop in temperature. The 12°C difference can make a tremendous difference to the stresses exerted on the substrate and can have a telling effect on its stability and heat gain. When it comes to roofs, having a darker shade in winter will not make much difference to how hot your roof – and home or building will get – as when it is cold they will be cold too, however in summer it will make a difference as to how hot your home or building will get by reflecting heat away from the building. Energy distribution of sunlight Visible, 44% Ultra-violet, 5% Infra-red, 51% Reflectance spectral curves for Resene Karaka Coolcolour™ versus Resene Karaka Total Solar Reflectance for Resene Hi-Glo Coolcolour™ versus standard colour VIS: 380-780mm Visible light Colour name Total Solar Reflectance Reflectance (%) Wavelength (nm) PAR: 400-700mm Photosynthesis active radiation 200 0 10 20 30 40 50 60 70 80 90 100 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 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. 70 |