iridescence by depositing ordered lattices of monodisperse particles onto a
film-forming polymer on top of keratin
(skin or fingernails). The particle layers
would act like a photonic crystal.
It’s all in the colors
Large cosmetic firms have huge computerized machines that select tiny
quantities of pigments and mix them
robotically. According to Draelos, an
experienced color designer can order up a
hundred different shades and then select
the ones that will form the company’s
color palette for the coming season.
Color artists use the principle of
blending complementary colors. For
example, a woman who wants to neutralize her reddish skin tone looks best
with makeup that contains tiny green
particles. Green, a complementary color
to the red, would make the skin appear
brown or tan.
Likewise, someone with a purplish
skin lesion could cover up flaws with
makeup with a yellowish tint. A bluish
tint in “color-lightening” lipstick will
help a person avoid the dreaded “yellow
teeth” look. The blue and red pigments
Simple light reflec-
tions are another
way to hide wrinkles.
Since the wrinkle is
depressed from the
skin surface, light-reflective particles
at the base of the
wrinkle will make
the crevasse reflect
more light.
will combine to yield a burgundy shade
that makes the teeth appear whiter.
“By allowing the optics of the eye
and light reflection to play with colors,
you can basically enhance certain color
perceptions by the eye and on the other
hand decrease certain color perceptions
by the eye,” Draelos said.
Using that principle of subtractive
color, cosmetic companies make opaque
concealers with green, violet and yellow
tints to hide specific skin problems,
Morante said. “But you have to know
how to use them so that you don’t walk
around looking like Herman Munster.”
The researchers developed a makeup
containing polysaccharide beads loaded
with enough titanium dioxide and red
iron oxide that the product itself falls
outside the desired skin-tone range, but
when applied to the skin gives the skin
a lowered spectral reflectance in that
“healthy look” 550-nm range.
Can science quantify our subjective
perceptions of facial coloration? According to Lei Huang and colleagues at Uni-lever, we get our idea of “healthy” skin
color from the absorption spectrum of
hemoglobin in the bloodstream. Spectral
reflectance of the skin has a “hemoglobin
dip” centered around 550 nm. On the
CIELAB L*a*b* color space scale (black
to white, green to red, blue to yellow),
Huang’s team defines light skin tones as
those with L* values between 55 and 70
and dark tones as those with L* measurements of 35 to 55.
Ideal mirror: 100% directional reflection
Ideal matte surface: 100% scattering
Directional reflection and scattering
Metallic gloss effect pigments
Absorption pigments
Pearlescent gloss effect pigments
ECKART GmbH
(Left) Metallic-effect pigments reflect light directionally, like a mirror. In cosmetics, their use is primarily in nail polish, and total reflectance is about 90 percent rather than the ideal 100 percent. (Center) Absorption pigments scatter light in all directions, resulting in an
even matte look. (Right) Pearlescent pigments reflect only part of the white light that enters them, giving an appearance of color that
depends on the location of the observer.
