Better than air conditioning, the world’s whitest white paint
Lab formula reflects 98% of light... and can cool buildings by 10C
AIR-CONDITIONING can be a saviour in those hot summer holiday months.
But it isn’t cheap – and contributes to greenhouse gas emissions.
Now scientists have discovered an eco-friendly way of cooling houses – in the form of a recordbreaking white paint.
The paint, hailed the world’s whitest, can send temperatures plummeting by 10C (19F) without using any electricity.
It has been created by an American team who pushed the limit on how white a white paint can be. Xiulin Ruan, professor of mechanical engineering at Purdue University, Indiana, said: ‘If you were to use this paint to cover a roof area of about 1,000 square feet (93 square metres), we estimate that you could get a cooling power of ten kilowatts.
‘That’s more powerful than the central air conditioners used by most houses.’ Researchers found the paint can keep surfaces 10C (19F) cooler than their surroundings at night. It also cools surfaces up to 4C (8F) below their surroundings under strong sunlight around midday.
The team believe this white may be the closest equivalent yet to the blackest black, ‘Vantablack’, which absorbs up to 99.9 per cent of visible light.
The formula reflects up to 98.1 per cent of sunlight, compared with the 95.5 per cent record set by previous white paint.
Typical commercial white paint usually gets warmer rather than cooler, and can only reflect 80 to 90 per cent of sunlight.
The ‘ultra-white’ paint’s reflectivity is down to its very high concentration of barium sulphate, a compound used in photographic paper and cosmetics. Barium sulphate particles are all different sizes, allowing the paint to scatter more of the light spectrum from sunlight.
Researcher Xiangyu Li said: ‘We looked at various commercial products – basically anything that’s white.
‘We found that by using barium sulphate, you can theoretically make things really, really reflective which means that they’re really, really white.’
There is scope to make the paint even whiter, the researchers said, but not much without compromising its durability. ‘You can’t increase the concentration too much,’ Mr Li said. ‘The higher the concentration, the easier it is for the paint to break or peel off.’
The team have filed patent applications for the formula.
‘Really, really reflective’