Article by: Kelly Dobos

In the part 1 of this series, I talked about the different ingredients that are used to create a pearlescent effect in cosmetics. In this part, I’ll talk about the science of how these ingredients produce different colors.

Two types of colors

Pearls can be described in terms of mass tone (absorption color) and interference color. In order to explain how these effects are achieved, we need to consider the physics of light. Visible light consists of a continuous range of wavelengths that compose the color spectrum. When visible light encounters an object like a particle of mica it can be reflected, refracted or transmitted. If the entire visible spectrum is reflected the particle appears silver white. If only part of the spectrum is reflected while others are absorbed, the pigment color is determined by the wavelength of the reflected light. A classic example is a red apple. The apple appears red because it is reflecting wavelengths in the red (700 — 635 nm) range.

Coated Mica

Coating mica and other substrates with thin, precise layers of titanium dioxide allows the wavelength of the reflected light to be tuned to produce a specific interference color (Figure 1). The overall mass tone of the mica is white, but with a change in viewing angle the interference color is visible. Black iron oxides and can also be used to create black pearls.


Figure 1. Interference Colors Produced by Layers of Titanium Dioxide

Deposition of other cosmetic colorants on top of interference pigments can create even more interesting effects. An absorption color can be matched with the interference color, for example iron blue combined with a blue interference color, to provide intensely colored pearls. Selecting an interference color that is complementary to the absorption color can also create two-tone effects. Combining carmine (absorption color) with yellow interference produces a pearl with a red mass tone and gold shimmer that is visible when viewed at different angles. A veritable rainbow of pearls is available from special effect pigment suppliers and they will often sample the cosmetic chemist a kit showcasing all of the options available. And, as with any color additives used in cosmetics you should refer to FDA and other global guidelines to ensure safety and compliance.

The next time you are out shopping, walk down the cosmetics isle and see what examples of pearl effects you can find. Or if you like to treat yourself to mani-pedi treatments as much as I do, check out OPI’s Pompeii Purple polish. It is a fuchsia polish with blue interference pigment.

Physics and nail polish, I do love my job.

Have you used pearls in your cosmetics?  What have you learned about formulating with them?  Leave a comment below.

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5 comments

  1. Kelly
    Kelly

    Kelly,
    Some pearls are on their way to you. I have included my contact information in the package if you have any futher questions. Good luck with your research! -Kelly Dobos

  2. Karen delgado

    Cool! Umm… Ok well since i’m working on pearls that are in makeup, they don’t necesarilly need to be pearls. There’s no specific type that i need, so really anything that you can get would be great! Thanks!

  3. Kelly
    Kelly

    Hi Perry and Kelly,
    I can try to help with this request, but I need more information on what type of pearls are wanted. There are many different options available. Thanks! -Kelly

  4. Karen Delgado

    hello, my name is Kelly, and Karen Delgado is my science teacher. We’re doing a science fair project on pearlescent makeup and we need a few samples to use for an experiment. If you have any extra samples that aren’t going to be used, please send them to our school. Our address is 165 Perryville Road Hampton, NJ 08827 and please put any packages under the name Karen Delgado. If you have any questions please e-mail me or call the school at
    908-735-5511
    thanks!

    1. Perry

      Thanks for contacting us. Unfortunately, we do not have extra samples to send out at the moment. But perhaps someone reading this will.

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