Optics & Photonics News - July/August 2010

Layered structure, thickness deviation

Borosilicate

Homogeneous thickness

[ Microscopic comparison of substrates ]

Microscopic view of uncoated substrates (mica vs. borosilicate)

Scanning electron microscope images of natural mica and synthetic borosilicate substrate particles reveal the more regular structure of the latter. Fewer steps and edges on the borosilicate flakes give them better reflectivity once they are coated with other substances. ECKAR T GmbH

Mica flakes (top) and borosilicate flakes (bottom), all coated with titanium dioxide. The smoother borosilicate particles give a brighter, more uniform color distribution and a better-looking final product. ECKART GmbH

sun-tanned, while another line of cosmetics might emphasize deep reds that flatter African American women.

Lipstick, eye shadow
and mascara

Lipsticks were originally made of wax crystals that are similar to wax polishes made for shoes and cars, Lochhead said. In recent decades, lipstick formulators have added polymers for more stability and tiny silicone resin cushions to reduce the likelihood that lip color will come off on coffee cups and shirt collars.

Today, lipsticks contain blends of red, yellow and blue lake pigments, sometimes with a dash of titanium dioxide to lighten reds into pinks. Synthetic “ pearl-izing” agents, such as bismuth oxychloride, give a frost or shimmer to the color. Lip glosses contain less wax and more oil than solid-stick lip colors.

Mascara must separate the eyelashes as well as color them. It needs to be as glossy and dark as the cosmetic scientist can make it, and its pigments must be compatible with polymers that have high extensional viscosity, so that the mascara forms a cylindrical film that adheres to the keratin in eyelashes.

However, the U.S. FDA gives research-
ers a limited choice in safe pigments for
use on eyelashes because of their proxim-
ity to the eyes’ mucous membranes,
Lochhead said. Another caveat for
mascara formulators is that, in the high
humidity at the eyelash level, the bot-
tom of each lash shaft swells more than
the tip, producing the characteristic curl
away from the eye. Completely water-
proofing the lashes would bar water
vapor from absorption into the lashes—
which would droop unattractively.

Looking ahead

According to Lochhead, “The reason
people don’t think there’s science in there
is that [cosmetics are] commonplace,” he
added. “People think that because they’re
so common, they can’t be very sophisti-
cated scientifically.”
Researchers are continuing to develop
new composite colorants that diffract and
scatter light without drawing attention
to themselves. Photonics, the ultimate
enabling technology, will undoubtedly
help millions more people to put their
best face forward to the world. t

Patricia Daukantas ( pdauka@osa.org) is the senior writer/editor of Optics & Photonics News.

[ References and Resources ]

>> P. Daukantas. “Photorealistic Rendering: Making the Virtual into Reality,” Opt. Photon. News 20( 1), 34 (January 2009).

>> C. Dumousseaux et al. “Compositions for Making Up Keratinous Materials,” U.S. Patent Application 20090117160 (May 7, 2009).

>> L. Huang et al. “Cosmetic compositions and method which impart a healthy appearance to skin,” U.S. Patent Application 20090155373 (June 18, 2009).

>> R. Johnson. “What’s That Stuff? Lipstick,” Chem. Eng. News 77( 28), 31 (July 12, 1999).

>> R. Y. Lochhead and L. Anderson. “Intellectual Property Trends in Color Cosmetics,” Household and Personal Products Industry magazine, August 2009; online at www.happi.com/

articles/2009/08/intellectual-property-trends-in-color-cosmetics.

>> M. Tan et al. “Compositions containing optical diffusing pigments,” U.S. Patent No. 6,511,672 (Jan. 28, 2003).

>> U.S. Department of Health and Human Services. “Cosmetics and Your Health: Frequently Asked Questions,” online at www.womenshealth.gov/faq/cosmetics-your-health.cfm.