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This white paint could help fight the climate crisis!4 min read

April 21, 2021 3 min read

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This white paint could help fight the climate crisis!4 min read

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Here’s a new way to fight the climate crisis – paint! Yes, you heard that right. This new paint produced by academic researchers, which is being called the ‘whitest-ever paint’, has been designed in such a way that it boosts the cooling of buildings.

Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab’s sample of the whitest paint on record. Credit: Purdue University

How does it do this? Glad you asked. This new paint reflects 98% of sunlight, and radiates infrared heat through the atmosphere into space.

When the paint was being tested, it was found to cool surfaces by 4.5C below the ambient temperature, or room temperature, even in strong sunlight.

Why white is important

Credit: NY Post

White-painted roofs have been used to cool buildings for hundreds of years. As global warming pushes temperatures up, the technique is also being used on modern city buildings, such as in Ahmedabad and New York.

Regular reflective white paints may be far better than dark roofing materials, but only reflect 80-90% of sunlight, and they absorb UV light. This means they cannot cool surfaces below ambient temperatures. The new paint does this, leading to less need for air conditioning and the carbon emissions they produce, which, along with temperatures, have risen drastically too.

“Our paint can help fight against global warming by helping to cool the Earth – that’s the cool point,” said Prof Xiulin Ruan at Purdue University in the US. “Producing the whitest white means the paint can reflect the maximum amount of sunlight back to space.”

Ruan said painting a roof of 93 sq-metres (1,000 sq ft) would give a cooling power of 10 kilowatts. “That’s more powerful than the central air conditioners used by most houses,” he said.

How is this paint so cool?

The new paint, which researchers say will be in the market in a year or to, was revealed in a report in the journal ACS Applied Materials & Interfaces. Three factors are responsible for the paint’s cooling performance. First, barium sulphate was used as the pigment which, unlike conventional titanium dioxide pigment, does not absorb UV light. Second, a high concentration of pigment was used – 60%.

Researchers testing the whitest paint. Credit: Purdue University

Third, the pigment particles were of varied size. The amount of light scattered by a particle depends on its size, so using a range scatters more of the light spectrum from the sun.

The barium sulphate paint enables surfaces to be below the ambient air temperature, even in direct sunlight, because it reflects so much of the sun’s light and also radiates infrared heat at a wavelength that is not absorbed by air.

The researchers said the ultra-white paint uses a standard acrylic solvent and could be manufactured like conventional paint. They claim the paint would be similar in price to current paints! They have also tested the paint’s resistance to abrasion, but said longer-term weathering tests were needed to assess its long-term durability.

Fighting climate change

White paint is already being used to combat the climate crisis. New York has painted more than 10 million square feet of rooftops white, according to BBC News.American NGO Project Drawdown calculated that white or plant-covered roofs could get rid of between 0.6 and 1.1 gigatons (a gigaton is 1,000,000,000 tonnes, and is often used when discussing human carbon dioxide emissions) of carbon between 2020 and 2050. The researchers hope their paint will enhance these efforts.

“We did a very rough calculation. And we estimate we would only need to paint one percent of the Earth’s surface with this paint — perhaps an area where no people live that is covered in rocks — and that could help fight the climate change trend,” Ruan told BBC.

So next time your parents want to get your house painted, you know exactly which colour to suggest!

Sources: The Guardian, Eco Watch, The Art Newspaper