Researchers at Purdue University have developed the whitest paint ever produced, capable of reflecting more than 98 percent of the light that strikes it, a quality that could reduce the need for air conditioning for buildings coated in the brilliant pigment. But perhaps even more ambitiously, another researcher calculates that if a mere one to two percent of the Earth’s surface were colored by this paint, the light reflected back into space could be enough to stabilize our decidedly out of control global temperatures.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts,” according to Purdue professor of mechanical engineering, Xiulin Ruan. “That’s more powerful than the central air conditioners used by most houses.”

Although current commercially-available white paints can be used to reflect sunlight away from the surfaces they’re applied to, they still absorb about 10 to 20 percent of the light that strikes them, meaning the surface absorbs enough energy to become warmer than its surroundings. But instead of using regular pigments, the Perdue paint uses a barium sulfate compound, a chemical already used to make photo paper and cosmetics white.

Additionally, the barium sulfate particles in the paint vary in size, allowing them to reflect different wavelengths of light, meaning the paint can reflect a broader spectrum of sunlight. These two qualities enable the new paint to reflect enough sunlight—98.1 percent—for the surface it’s applied to to lose more energy than it’s receiving, cooling it below the surrounding temperature.

“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” explains Purdue Ph.D. candidate Joseph Peoples.

But what if this paint were used on a portion of the planet to increase the Earth’s albedo, its ability to reflect light? According to the calculations of University of California professor of electrical and computer engineering Jeremy Munday, we would only need to cover between one and two percent of the Earth’s surface to reflect enough sunlight back into space to offset the energy trapped by global warming.

While this doesn’t seem like it would require a huge effort to accomplish, this means we would have to cover a portion of the Earth that is between five and ten million square kilometers (1,930,000 to 3,860,000 square miles)—an area close to the size of Canada—requiring between 139 and 278 billion gallons of Perdue’s paint to complete the job.

Even if we don’t resort to covering large swaths of the planet in super-pale pigments, simply painting surfaces white can help control rising heat levels at a local level; for instance, Los Angeles is painting streets and roadways white, to prevent the dark asphalt from absorbing sunlight; and simply coating one’s roof with ordinary white paint can reduce the temperature of the house by a number of degrees, with some houses in Indonesia seeing temperature reductions of over 10°C (18°F) as part of the Million Cool Roofs Challenge.

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  1. Great idea and application. Hopefully there will be incentives and rebates for using the paint. I’m ready!

  2. This article seemed pretty neat thinking about how much energy I could save……but when I started reading about increasing Earth’s albedo by painting an area the size of Canada, it started to bother me. Like looking down a slippery, icy slope into an ice age. Is this not what happens when the planet is covered in ice?

    Why don’t we give control of Mother Earth back to the Creator? I’m sure he/she/it (The Creator that is) would reduce the greenhouse gases by cultivating more trees and providing more oxygen to those who could really use it, like us. Back to the win/win situation as originally intended.

    Painting the Earth just sounds so Brandon.

    1. The exercise was entirely academic, so you don’t need to worry about anyone actually trying to paint a sizable portion of the planet: aside from almost all of that area already being used (especially by natural carbon sinks), such an endeavour would consume the entirety of the planet’s paint production for more than a quarter century.

      That’s not even considering the ecological devastation that would result from essentially paving over 1/50th of the planet, and producing more than a quarter trillion gallons of paint.

      Nobody was taking the idea seriously–especially the author–it’s just a good way of illustrating exactly how reflective this substance is, and how little it took to throw the planet’s climate out of whack.

      1. That said, encouraging the use of this or any other reflecting white paint would reduce utility costs and the use of fossil fuels. I think developing this paint also had that in mind.

  3. Taking sequestered carbon out of the ground was done by us and wasn’t “natural”. Seems that we should try and fix it. Planting trees while nice doesn’t happen quick enough. Not doing anything by denial and hoping for supernatural intervention seems too Trumpy.

  4. What about the effects of particles of barium eroding as the paint wears away? How would that affect the environment? I know the ‘Purdue paint’ question is academic, but we really need to think about how even short-term solutions can have long term effects downstream from their application(s). I need to replace the roof on my house before this winter and I will be putting a light colored roofing material on it for sure!

  5. Barium sulfate already sees a fair amount of industrial use, and as a non-soluble salt it is chemically stable has little environmental impact–basically, it can be ingested, but because it isn’t readily absorbed into the bloodstream it just passes uneventfully through the digestive tract.

    However, if it were elemental barium, that’d be a different story: the metal is extremely reactive, and as a result is very toxic; that high reactivity is why the elemental form of barium is never found in nature.

    This is something in chemistry that is overlooked by most laypersons: different configurations of the atoms within a compound can produce extremely different properties. For instance, two oxygen atoms (O2) are vital for the continued minute-to-minute health of aerobic organisms like humans; add a single carbon atom to that arrangement (CO2) and the compound becomes metabolically inert; and drop a single oxygen atom from that arrangement (CO) and the compound is a toxin deadly enough for our civilization to have to build specialized detectors to make sure that its not accumulating in our homes.

    Just three different combinations of the same two elements, carbon and oxygen, ranging from life-sustaining to downright lethal.

    But regarding barium sulfate, we don’t have to worry about the barium in BaSO4 “eroding” away from the oxygen and sulphur it’s bound to, since those bonds are extremely strong. Think about how often hydrogen atoms fall out of water molecules: it just doesn’t happen.

  6. Stardust and everyone, in the UC members’ Message Board, I added a link for information on what vendors of roofing materials call a “cool” roof my family just had installed on our house in Los Angeles county. Please see the Climate Change thread, in the “Hope vs. Doom and Gloom” sub-category. As you can see on that vendor link, “cool” roofs actually come in a variety of colors.

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