Blue light beats bleach for yellow stains
Sweat spots are the worst enemy of a white t-shirt. Unfortunately, this yellowing of the notorious fabric is often inevitable due to the combination of oleic acid, squalène and other organic compounds found in oil and the perspiration of your skin. Factor in a fortuitous meeting with natural food pigments such as carotene and lycopene found in tomatoes and oranges, and it is probably only a matter of time before you had to break the bleach or hydrogen peroxide. Even then, the results are often not satisfactory for your white (once) vibrant shirts.
However, new research indicates that there can be another strategy to restore clothes to their old glory. It may be time to exchange hard chemicals and solvents for high intensity blue LED light, according to a study recently published in the journal ACS chemistry and sustainable engineering.
How oxidation cleans spots
Tissue whitening solutions such as laundering or hydrogen peroxide work through a process called oxidation. Take the dreaded ketchup stain as an example. The rest of the blood visible on the fabric is visible due to light wavelengths which remain not absorbed by the chemical composition of the condiment. The introduction of an oxidant like Bleach separates carbon atoms with double bond of the task responsible for the absorption of light. With enough atomic deterioration, the coloring absorbs so few wavelengths that it appears white again to the human eye. Ketchup chemicals can always stay on your cotton shirt, but they are essentially invisible.
Unfortunately, many popular chemical oxidants are always harmful to the environment, while the purchase of new clothes is simply not durable. Induce oxidation without Hard solvents or a renewable wardrobe would be an ideal way to help keep clothes clean and the healthy planet. Now, researchers in Japan may have finally understood this puzzle.
Heal the blues of the yellow spot
The chemists Tomohiro Sugahara and Hisanari Yoneda found that the irradiation of high intensity blue LED light eliminates the yellowing that occurs in the polymers of elderly resin during a previous study. They quickly wondered if the principles of the sample applied to fabric spots without damaging the material itself.
“Our method uses blue light visible in combination with ambient oxygen, which acts as the oxidizing agent to drive the photoblancing process,” Sugahara said in a press release. “This approach avoids the use of hard chemical oxidants generally required in conventional laundering methods, which makes it intrinsically more sustainable.”
First, the pair exposed vials of beta-carotene, lycopene and squalène to a high intensity blue LED light for three hours each. Each sample has lost the color, while a follow-up analysis confirmed that the oxygen content of the ambient air itself has contributed to moving along the photoblaching process. Then, they stamped the cotton fabric samples with squalène before heating them to simulate an aging stain. From there, the team tested three spots for removing stains: a hydrogen peroxide bath, or exposure to blue LED or ultraviolet light (UV).
The results were unambiguous: blue light surpassed the options of hydrogen and UV peroxide. With UV light, treatment has actually generated new compounds tinged with yellow. Other experiences have shown that blue LED treatments have safely lit similar squalène spots on silk and polyester, while attenuating spots from common compounds of stains such as oleic acid, tomato juice and orange juice.
Sugahara and Yoneda always want to carry out additional longevity and security tests before trying to market the system, but believe that it is in the field of the possibility that a small LED light could soon contribute to extending the lifespan of your clothes. Avoiding new food stains will always be your responsibility.
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