Website Gizmodo had an amusing find over the weekend, an article about how LEDs, which don’t illuminate much in the ultraviolet spectrum, fail to excite certain laundry detergent ingredients that “make your whites look whiter.”
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.
[…] Unfortunately, most of the commonly-available LED lighting today emits little or no light in the ultraviolet part of the spectrum. And as a research team led by Penn State's Dr. Kevin Houser discovered, that makes FWAs pretty much useless.
It seems unlikely that lighting manufacturers would change their technology to preserve detergent-makers’ power to deliver this illusion, but then again, if customer’s shirt looks brighter and cleaner to him under a demonstration light that includes ultraviolet wavelengths and therefore is more likely to buy...? Well, it’s all about satisfying the customer, isn’t it?
Gizmodo: LED Lights Are Ruining Laundry Detergent's White-Brightening Trick