Back in the day, I was a chemist for P&G. Almost all laundry detergents have a “brightener” added, to counteract the faint off-white cast of laundry. As described, they absorb UV, and emit blue, which counteracts the slight yellow cast of the laundry. Before the advent of brighteners, housewives would add “bluing" to the final rinse. Bluing was a shaker bottle of a suspension of blue dye. See https://en.wikipedia.org/wiki/Optical_brightener for more details. -- Vincent Heuring Professor Emeritus Dep't of Electrical, Computer, and Energy Engineering University of Colorado at Boulder h) 73335 Pinyon St, Palm Desert CA 92260 heuring@colorado.edu c)720-346-4635 http://ecee.colorado.edu/~heuring

On Jun 18, 2019, at 12:00 PM, colorsync-users-request@lists.apple.com wrote:

There’s nothing like a free lunch. Through OBA’s the paper industry succeeded to turn paper into mini displays (capture UV-light and emit as blue light).