Sweat and food stains can ruin your favorite clothes. But bleaching agents such as hydrogen peroxide or dry-cleaning solvents that remove stains aren't options for all fabrics, especially delicate ones. Now, researchers in ACS Sustainable Chemistry & Engineering report a simple way to remove yellow stains using a high-intensity blue LED light. They demonstrate the method's effectiveness at removing stains from orange juice, tomato juice and sweat-like substances on multiple fabrics, including silk.
It’s definitely not fast, but at 10 minutes per spot it’s still plausible to set up some kind of sweep to slowly cover an entire item and let it run for a while. But you’ll absolutely need a stronger source than a flashlight, unless you’re only targeting small spots. 200 W seems plausible, which gives you ~20x the surface area (50 cm^2 every 10 minutes)