Ruan Xiulin, a professor of mechanical engineering at Purdue University, and his students created the whitest paint ever recorded. (Purdue University Photo/John Underwood)

West Lafayette, Indiana — Want to save a lot of air-conditioning costs? Wait a few years and paint your home with the whitest paint in the world, which may greatly reduce or even eliminate the need for air conditioning.

This paint developed by Purdue University won the title of Guinness World RecordsTM. The record appears in the 2022 edition of the Guinness Book of World Records and is available for purchase from Thursday (September 16).

Breaking the record for the whitest paint is not the researcher's goal-it is to curb global warming.

"About seven years ago, when we started this project, we thought about saving energy and tackling climate change," said Ruan Xiulin, a professor of mechanical engineering at Purdue University in the "This is Purdue University" podcast.

Ruan and his graduate students invented the pigment together. The idea is to create paint that can reflect sunlight away from the building. However, to make this paint truly reflective, it also makes it truly white. The formula created by Ruan’s laboratory reflects 98.1% of solar radiation while emitting infrared heat. Since paint absorbs less heat from the sun than it dissipates, the surface coated with this paint will cool below the ambient temperature without consuming electricity.

Typical commercial white paint will become warmer rather than colder. The coatings on the market designed for heat dissipation can only reflect 80%-90% of the sunlight and cannot make the surface cooler than the surrounding environment.

Purdue University researchers showed in a published paper that using this new coating formula to cover about 1,000 square feet of roof area can generate 10 kilowatts of cooling power. "This is more powerful than the air conditioner used in most houses," Ruan said.

This white paint is the result of an attempt to develop radiant cooling paint as a viable alternative to traditional air conditioners in the 1970s. Ruan’s laboratory considered more than 100 different materials, reduced them to 10, and tested about 50 different formulations for each material.

Two properties make this paint super white: a very high concentration of a compound called barium sulfate-also used in photographic paper and cosmetics-and barium sulfate of different particle sizes in the paint. The wavelength of sunlight scattered by each particle depends on its size, so a wider particle size allows the paint to scatter more of the spectrum from the sun.

A little space can make the paint whiter, but it will not affect the paint.

The researchers worked with a company to expand the scale of the coating and put it on the market. The patent application for this coating formulation has been submitted through the Purdue Research Foundation Technology Commercialization Office. For further discussions on this intellectual property, please contact Will Buchanan at wdbuchanan@prf.org and refer to the tracking code PRF 2018-RUAN-68168. Information about this technology and other Purdue technologies can be found online.  

This research was supported by the Purdue University Cooling Technology Research Center and the Air Force Scientific Research Office through the National Defense University Research Instrument Program (approval number: 427 FA9550-17-1-0368). The research was conducted at Purdue University’s FLEX laboratory and Ray W. Herrick’s laboratory and at the Burke Nanotechnology Center in Purdue University’s Discovery Park.

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Writer and media contact: Kayla Wiles, 765-494-2432, wills5@purdue.edu

Source: Ruan Xiulin, ruan@purdue.edu

Note to reporters: Photos of B-roll and white paint research are available through Google Drive. Journalists visiting the campus should follow the visitor health guidelines.

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