George - 11 February 2013 09:48 AM

Lois - 11 February 2013 08:04 AM

TimB - 30 November 2012 06:58 PM

Ok, I think I’m almost there.  So is this correct?: Mixing all of the colors of filtered light, would result in white, (or maybe, better to say, unfiltered light is white, and filtering separates it into colors).  Whereas mixing all the different color sources of reflected light results in black.

Unless you’re mixing paint.  Mix all colors and you get mud, not white.

Tim meant you get white when you mix all light. When all the light gets absorbed, as in black chalkboard, say, no light will be reflected and you’ll see black. He is right, of course.

I know.  Just wanted to make a practical point.

Since aerospace coatings and their pigmentation was one of the areas my company was involved in, I was fascinated by a project to make coatings that appeared “white” (totally reflective) in infra-red since some anti-aircraft guided missiles homed in on the dark appearance of most coatings in that range.  Although it was not my field, for the fun of it, I was able to use that department’s computer to come up with a coating that was completely black in visible light, but “white” in infra-red.  It looked fine until they put it on the roof for sunlight exposure.  After a month the blue and green pigments faded and it changed from black to a muddy red.  I decided to go back to polymers and let the paint people diddle with their pigments.

Occam