Can the world's whitest color save the Earth?

The American Purdue University has invented a white paint that can "cool" the planet, revolutionizing the challenge of climate change. The innovative formula of this paint is able to reflect back 98.1 percent of the sun's rays.

Purdue University here in the United States has created a type of white ink that could mark a turning point in the challenge of global warming.

The professor of mechanical engineering of this university has used the ability of white, a color that absorbs less heat, to create this special paint.

Reporter John Yang from the American public television network PBS brings details of this extraordinary story of innovation.

Of all the colors, white absorbs the least amount of heat.

To make it more clear.

White is the color that Purdue University mechanical engineering professor Xiulin Ruan says could help tackle climate change. Professor Ruan together with some of his students, conducted several years of research work to invent a new white paint that can cool the planet.

"What needs to be done is to paint less than 1 percent of the earth's surface with this white paint, it doesn't matter if it's roofs, roads, cars. We would be able to completely reverse global warming and bring temperatures back to the level we would like them to be."

The white paint currently marketed is widely used in hot climates because it reflects 80 to 90 percent of the sun's rays, keeping surfaces from getting too hot. But Professor Ruan aimed for even more, something that could cool surfaces.

“Our paint reflects 98.1 percent of the sun's rays, which means it only absorbs 1.9 percent of the rays, so almost zero heat from the sun. Commercially available white ink absorbs 10 to 20 percent. So basically, we are reducing the sun's heat penetration by a factor of 10. It's really something big."

One of Professor Ruan's PhD students, Joe Peoples, explains what makes this type of ink different.

The new ink uses concentrated amounts of barium sulfate, a chemical compound used in cosmetics, as well as to brighten the paper used to wash photographs.

Many people think this is too dangerous. Actually it is not. It is actually safe. Those who do bowel radioscopy actually drink barium sulfate beforehand so that the bowel becomes visible through X-rays.

“This will produce 50 to 100 milliliters of ink. It will take about 18 hours. This tile is painted with the whitest paint we could find on the market. Reflects 88 percent of the sun's rays. And this is our barium sulfate plate, which reflects back 98.1 percent of the rays."

Even with the unaided eye, the white that is created appears brighter than the other

And when I touch it with my hand, the tile is cooler.

"Exactly. This is absorbing more solar energy so it is getting hotter. This other is absorbing less and is below ambient temperature.

On this sunny day, where the temperature is 22 degrees Celsius, the plate painted with the new paint was about 8 degrees less than the one painted with the market-bought paint and almost two degrees less than the ambient temperature.

Asked if he thought this could eliminate the need to use air conditioning, he replied:

"It is possible to eliminate the use of air conditioning in some areas and at a certain time of the year. If it is used in Phoenix, Arizona, or Reno, Nevada, there can be up to a 75 percent reduction in air conditioning use during the summer."

Professor Ruan says this paint is more environmentally friendly than paints currently on the market. It took the team more than 7 years of research to conduct tests on 100 different materials before they managed to find the correct formula.

What was the moment you realized that your research was successful, that it was cooling below ambient temperature?

"As you can imagine, my research for my PhD was about watching paint as it dried."

And when we finally got a result for something we had been working on for so many years, it was really rewarding."

"I started thinking, people all over the world are interested in this, they need affordable ways to cool the environment. But apart from that, we need to find solutions to climate change. Our work may have a wider impact than we thought."

They have applied to obtain the patent that gives them the right of authorship of the formula and are collaborating with a large paint company in the hope that the paint would be used more widely by the population./VOA