'Whitest paint' that reflects more than 98% of light is developed, too white to cool objects


by Purdue University / Jared Pike

'The whitest paint in history' that reflects 98.1% of light has been 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 infrared rays that carry heat to prevent objects from being warmed by sunlight. It can be used for cooling 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 can prevent the surface from heating by sunlight and reduce the operating rate of air conditioning, so Nobel Laureate in Physics Winner Steven Chu said, ' To prevent global warming, roofs around the world should be used. It should be painted white . '

Therefore, the research team of Mr. Siurin Luang, a professor of mechanical engineering at Purdue University, researched more than 100 kinds of materials, selected 10 kinds from them, and tested each material in 50 ways. We have developed a white paint that reflects 95.5% of the color. From the following article, you can see a movie of the experiment to actually check the cooling effect using paint.

'Ultimate white paint' that reflects 95.5% of light is developed --GIGAZINE



After a lot of trial and error with the aim of improving paints, the research team focused on barium sulfate, which is widely used in cosmetics, pharmaceuticals, and pigments. We found that barium sulphate, sometimes referred to as 'blanc fixe' in French, can be used as a paint to achieve higher reflectance than previous paints made from calcium carbonate.

The following is a picture of the newly developed paint-coated board exposed to sunlight with a normal camera (left) and an infrared camera (right). Looking at the photo on the right, it can be seen that there is a cooling effect not only on the paint itself but also on the painted object because the part where the white paint is applied and the color of the board on which the paint is applied are dark. I will.


by Purdue University / Joseph Peoples

This paint is so white because the particles of barium sulphate are non-uniform. Since the amount of barium sulfate particles that scatter light 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 sunlight. This means that only 1.9% of the heat is absorbed, and the cooling effect is twice that of the previous paint. Thanks to this cooling effect, painted objects were 4.4 degrees cooler than their surroundings even in sunlight and 10.5 degrees cooler at night.

'It's estimated that applying this paint to a 1000-square-foot roof will provide a cooling effect equivalent to 10 kilowatts, which is better than the air conditioners used in most homes. It's powerful. ' The technology used by Luang et al. To develop this paint is compatible with the process of manufacturing commercially available paints, so it is easy to put it to practical use.

in Science, Posted by log1l_ks