The ``whitest paint'' that reflects more than 98% of the light is developed, the object that is too white cools down


by Purdue University/Jared Pike

The 'whitest paint in history' that reflects 98.1% of light was developed by engineers at Purdue University in the United States. Paired with

Vantablack , the 'blackest substance on earth' that absorbs up to 99.9% of light, this paint reflects not only visible light but also heat-conducting infrared light , preventing objects from being warmed by sunlight. , it can be used for air conditioning and global warming countermeasures.

The whitest paint is here – and it's the coolest. Literally. - Purdue University News
https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..html

World's Whitest Paint: How Can It Fight Global Warming? | Science Times
https://www.sciencetimes.com/articles/30695/20210415/world-s-whitest-paint-science-invention-help-fight-global-warming.htm

Reflecting sunlight on a white roof prevents the sun from heating the surface of the earth and reduces the operating rate of air conditioners. It should be painted white .”

Therefore, a research team led by Mr. Siu Lin Luan, a professor of mechanical engineering at Purdue University, studied more than 100 types of materials, selected 10 types from them, tested each material in 50 ways, and tested 'light We have developed a white paint that reflects 95.5% of From the following article, you can see the movie of the experiment to actually check the cooling effect using paint.

``Ultimate white paint'' that reflects 95.5% of light will be developed - GIGAZINE



After further trial and error with the aim of improving the paint, the research team focused on barium sulfate , which is widely used in cosmetics, pharmaceuticals, and pigments. By using barium sulfate, which is sometimes called 'eternal white (blanc fixe)' in French, we found that it was possible to achieve a higher reflectance than the previous paint made of calcium carbonate.

Below is a picture of the board painted with the paint developed this time exposed to sunlight with a normal camera (left) and an infrared camera (right). If you look at the photo on the right, you can see that there is a cooling effect not only on the paint itself, but also on the object it is painted on, as the areas where the white paint is applied and the painted board are darker. increase.


by Purdue University/Joseph Peoples

This paint is so white because the barium sulfate particles are non-uniform. Since the amount of light scattered by barium sulfate particles depends on the size of the particles, it seems that the larger the difference in particle size, the more the spectrum of light contained in sunlight can be scattered.

When the research team measured the reflectance of the paint, it was found that the paint developed this time can reflect 98.1% of the sunlight. This means that only 1.9% of the heat is absorbed, and the cooling effect was twice that of the previous paint. Thanks to this cooling effect, the painted object was 4.4 degrees cooler than its surroundings in daylight, and 10.5 degrees cooler at night.

``A 1,000-square-foot (about 93-square-meter) roof is estimated to have a cooling effect equivalent to 10 kilowatts, which is more than the air conditioners used in most homes,'' Ruan said. It's powerful,' he said. The technology used by Ruan et al. to develop this paint is compatible with the process of manufacturing commercially available paint, so it is easy to put into practical use.

in Science, Posted by log1l_ks