Acrisp white shirt can be a dangerous thing. It seems to invite a spurt of ketchup or a dribble of soup or a splatter of butter. To put one on is to pin your hopes on an intensive — or expensive — laundering process that may not even work.
Luckily, this is a problem that scientists have been pondering for as long as whites have been bright. And a breakthrough could be on the way: according to a study published recently in the journal ACS Sustainable Chemistry and Engineering, intense blue light can buff away those ugly spots and spatters.
“We were surprised by how effective the process turned out to be,” said Tomohiro Sugahara, a researcher with the Asahi Kasei Corp. in Japan and an author of the study. “Seeing it work so well on yellowing in actual dress shirts was especially striking.”
Using light to launder clothes is not new. Rays from light’s ultraviolet spectrum, including those found in sunshine, can break down stains and pigment; that is why your favourite T-shirt fades over time. And professional cleaners sometimes use ultraviolet light to treat sullied clothes and fabrics.
But they often need added agents like hydrogen peroxide, high concentrations of which can be corrosive to some materials and harmful to people. Scientists have been searching for stain-removal methods that are safer and more environmental friendly.
Sugahara and his colleagues’ approach used light from a different part of the spectrum. It had a wavelength of 445 nanometres, which, unlike ultraviolet or infrared light, is within humans’ range of visibility. It registers, to us, as a rich indigo-blue.
The researchers found that after textiles were blasted with blue light for 10 minutes, the stains degraded on a molecular level and became colourless, with help from oxygen in the air. The stains were made from compounds that are typically found in human sweat, skin oils and foods including pumpkins, peppers, sweet potatoes and tomatoes.
This was a contrast with the traditional ultraviolet rays, whose performance was mixed. The blue light was also gentler on delicate fabrics like silk, and it did not require harsh chemicals.
The method was not limited to white fabrics. According to Sugahara, the blue light did not discolour sample fabrics that were blue, or even checkered black-and-white. He added that researchers planned to test fabrics of more colours and to perform additional studies to establish the method’s safety.
Juan P. Hinestroza, a professor of fibre science at Cornell University, US, said that the research was an “important development” with clear potential for commercial use, as well as environmental benefits.
“The fact that the light at 445 nanometres does not damage the fibres is very important,” said Hinestroza, who was not involved in the study and directs a textile nanotechnology laboratory. “Traditional washing generates a lot of microplastics, and this method appears to minimise the use of mechanical forces and water to eliminate the stains.”
He added that cleaning methods that were gentle on fabric, as blue light appears to be, could help people hang onto their clothes for longer, reducing waste.
Sugahara said that the blue light stain removal could become available for practical use — perhaps for dry cleaners, as well as bridal and costume rental companies — within five years.
NYTNS