LED lights are ruing "whiter than white" detergent claims

For years, companies have been adding whiteners to laundry detergent, paints, plastics, paper and fabrics to make whites look “whiter than white,” but now, with a switch away from incandescent and fluorescent lighting, different degrees of whites may all look the same, according to experts in lighting. “Retailers have long been concerned with the color-rendering qualities of their lighting, but less aware how light sources render white,” said Kevin W. Houser, professor of architectural engineering, Penn State.

LED lighting is great. The right bulb gives the same warm incandescent glow you love from a fraction of the energy. But there’s a downside: while LEDs make cities look awesome, the most common type of LED lighting dims the ultraviolet trick laundry detergents use to make white clothes look whiter. The future is bright, but it’s also kind of dingy. There’s some fascinating science going on here. Many laundry detergents contain fluorescent whitening agents, or FWAs, which absorb ultraviolet light and re-emit it as a visible blue wavelength. This slightly bluish tinge helps overpower the yellowish hue of, say, a well-worn undershirt, making that nasty old rag look radiant and white.

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