The blackest black in the world is so dark that we are running out of superlatives.
The so-called Vantablack absorbs 99.965 percent of the light and is therefore so black that our eyes can no longer see and focus on the surface structure.
Researchers at Purdue University in the US state of Indiana have now developed the equivalent:
The whitest white in the world.
This ultra white reflects 98.1 percent of the light.
For comparison: the white color previously available on the market reflects 80 to 90 percent of the light.
As the scientists write in the journal “ACS Applied Materials & Interfaces”, measurements have shown that surfaces painted white are four degrees Celsius cooler than their surroundings, even in the midday heat.
At night it is even 10.5 degrees.
The photo shows a board coated with the ultra-white paint (left).
But only an infrared camera (right) from the same board makes it clear that it is cooler than its surroundings.
Source: Purdue University / Joseph Peoples
“If you treated a roof of around 1,000 square feet (92.9 square meters) with this paint, you could get ten kilowatts of cooling.
This is more powerful than the air conditioning systems that are used in most homes, ”explains mechanical engineering professor and head of studies Xiulin Ruan in a press release.
Because of this cooling property, the scientists hope that their color can make a contribution in the fight against global warming.
Because with it whitewashed surfaces such as roofs and streets cool down cities and can thus replace energy-guzzling air conditioning systems.
Last year, Xiulin Ruan and his colleagues had already developed a white that reflects 95.5 percent of the light.
However, that was not enough for them and they continued to search “for basically everything that is white”.
We found that with barium sulfate, in theory, you can make things very, very reflective, which means they get really, really white.
Xiangyu Li, PhD student at Purdue University
If they used calcium carbonate, i.e. lime, for their first color, the scientists now rely on barium sulfate.
This sulfuric acid salt is used in many ways, for example as a filler material in plastics and paper, in the extraction of raw materials in the oil and natural gas industry, as a contrast medium in radiology and as a pigment in paints and varnishes.
Of course, barium sulfate (BaSO4) occurs in the mineral barite or barite
Source: pa / imageBROKER / Richard Becker / FLPA
The secret of ultra white
Xiulin Ruan and his team not only used a lot of barium sulfate for their color, but also used the particles in different sizes from 270 to 530 nanometers.
Because how well a particle scatters light also depends on its size.
Many different sizes mean a higher reflection, so that even infrared light is reflected back.
According to the scientists, the new Purdue white could hit the market in a year or two.
It should be as resistant as conventional exterior paint.