Holo vs. iridescent vs. duochrome—what’s the difference?

[indylovesmakeup]

I saw some reviewers were irritated that UD is calling their new highlighters “holographic.” Instead, the products are apparently iridescent. I thought they were basically the same thing but I guess not. Can someone help me with the difference between these (and also duochrome)? I am confused. Thanks!

[rachelm13]

Holographic means that it shifts rainbows iridescent means it shifts from one colour to another

[joshlinc]

Holographic is a specific term. A holographic item breaks the spectrum of light and the same fleck of glitter will reflect the whole spectrum of the rainbow. So a holographic item will show red, blue, green, purple and yellow depending on how the light hits it. You would have the item with different colors glinting off it it.

Iridescence is reflective and glittery, but only one color, so it appears to glow. So a yellow iridescent item will reflect and appear to glow, but will only be yellow. 

Duochrome is iridescent with 2 colors, usually a metallic pigment in one color and a glitter in another, for example of the major duochrome eyeshadows most brands have one that is a brown color from one angle and green from another.

[Baranduin]

I don't think that is correct. Holographic and Iridescent have long standing meanings, and their meanings seem to have been refined for use in nail polish and then makeup. Iridescent has NEVER meant that it was one color, it has ALWAYS meant that it shifts between a range of colors, at least two, but with shades in between. In the makeup industry (nailpolish), iridescent seems to have come to refer to materials with the capacity to color shift, and which are ALSO transparent, not opaque. The transparency is, I believe, what gives them their glowy quality. But to be iridescent, a material must reflect more than one color.

The difference between iridescent and holo then, is, at minimum, that holo refracts the full rainbow where iridescent covers only a portion of it. 

My guess for duochrome (and I am less confident about this guess) is that it is an iridescent-type material that is opaque. But these are all industry secrets, which is stupidly annoying. The small percentage who really care about construction are probably already competitors and know these basic classifications.

[curlychiquita]

That's very informative, @joshlinc, thank you!