United States.
Scientists at the Berkeley lab have determined that certain dark pigments can stay as fresh as whites, using fluorescence, the re-emission of absorbed light.
Researchers have tested this concept by coloring thermal roof coatings with ruby red (chromium-doped aluminum oxide). Led by Berkeley Lab scientist Paul Berdahl, the first thing they found is that the white paint coated with a layer of ruby crystals stayed as fresh as a commercial white layer. They then synthesized the ruby pigment to mix it into the coatings.
Substantial research in recent years found that reflective roofs and walls can cool buildings and cars. This reduces the need for air conditioning and mitigates the urban heat island effect. By reflecting the sun's rays back into space, these cool materials also release less heat into the atmosphere, cooling the planet and offsetting the warming effects of substantial amounts of greenhouse gas emissions.
This opens the door to darker colors not only for cool ceilings but also for other objects that undergo prolonged periods of sun exposure, including vehicles, ships, storage tanks and PVC pipes.
Using fluorescence or photoluminescence, for fresh materials it is a new concept, and Berdahl, who is a physicist by training, has a patent pending for the technology. "People understand that materials that fluoresce emit energy," he said. "What's new here is the use of the fluorescence process to keep buildings cooler."
Source: Berkeley Lab.
