Article: Purdue University researchers have unveiled an “ultra-white” paint that reflects 98.1 % of incoming sunlight, a level of solar reflectance far above the 80-90 % typical of existing cool-roof products.
How the paint works
The paint’s brilliance comes from barium sulfate, a mineral already used in cosmetics and photography for its bright whiteness. Purdue’s team spent six years testing more than a hundred candidate substances before settling on a mixture of barium-sulfate particles in a range of sizes. The varied particle dimensions scatter sunlight across a broader spectrum, sending most solar energy back into space instead of heating the surface beneath.
In full sun, a surface coated with the new formulation stayed about 4.5 °C cooler than the ambient air. After sunset, the same surface kept losing heat through radiative cooling, about 10.5 °C below the surrounding air temperature. In practical terms, a 1,000-square-foot roof treated with the paint would dissipate heat comparable to a 10-kilowatt air-conditioning unit, but without drawing any electricity.
Why India stands to benefit
India’s summer months regularly see peak electricity demand spike as households and businesses run air-conditioners at full blast. The surge strains a grid that already struggles with capacity gaps and forces utilities to fire up costly, fossil-fuel-heavy peaker plants. By lowering buildings’ cooling load, the paint could flatten those peaks, easing pressure on the national grid and reducing the need for additional generation capacity.
In densely built metros, concrete, asphalt and unshaded roofs absorb and re-radiate heat, creating urban heat islands several degrees hotter than surrounding rural areas. A city-wide rollout of a high-reflectance coating would raise the albedo of rooftops and façades, pulling more solar energy back into space and pulling city-wide temperatures down.
For low-income households, the paint offers a passive, low-maintenance solution. Applying it uses the same tools and techniques already familiar to local painters, so the upfront cost can be spread over the coating’s life, while electricity bills for air-conditioning drop sharply.
From lab to market
The Purdue team designed the formula to slot into existing industrial paint-manufacturing lines. No radical retooling is required, a factor that speeds the path from laboratory to storefront. The project received backing from Purdue’s Cooling Technologies Research Center and the U.S. Air Force Office of Scientific Research, and the researchers have already filed patent applications. Durability testing shows the coating resists cracking and peeling, addressing a common criticism of earlier cool-roof technologies that degraded quickly under harsh weather.
Takeaway
Purdue’s ultra-white paint shows that a relatively simple material tweak can deliver a dramatic jump in solar reflectance, offering a low-energy pathway to cool buildings and cities. For a nation like India, where soaring temperatures drive ever-higher electricity demand and exacerbate urban heat islands, the coating could become a cost-effective tool in the climate-adaptation toolbox—provided the economics of large-scale deployment are addressed and real-world performance matches the promise.