J. Cosmet. Sci., 66, 189–205 (May/June 2015) 189 Enhancing skin radiance through the use of effect pigments DAVID FUNK, BRANDON KOVAROVIC, GABRIEL UZUNIAN, JILL LITCHAUER,TRICIA DALEY-BOWLES, and AMBER HUBSCHMITT, BASF Corporation, Tarrytown, NY 10591 (D.F., B.K., G.U., J.L.), and BASF Corporation, Stony Brook, NY 11794 (T.D., A.H.). Accepted for publication April 10, 2015. Synopsis In this study, the radiance contribution from formulating various pearlescent effect pigments into a skin cream was modeled using gloss map histograms created from digital photographs of clinical panelists. CIELab color data from the various pearlescent effect pigments applied to simulated skin tone drawdown cards was fi rst collected to screen experimental candidates and to help select the concentration of pigment used in the formula. Optical microscopy was used to develop a simple coverage model to control for the dif- ferences in particle size and density of the effect pigments. In the subsequent in vivo study, panelists applied a weighed amount of cream containing various pearlescent effect pigments to the face and high-resolution digital photography images were collected on each panelist for image analysis. Gloss map histograms were developed through the software analysis of gray-scale images, which were used to describe the gloss, whiteness, and/or radiance contribution of each pearlescent effect pigment. The resulting gloss map histograms shared identifi able characteristics useful for statistical analysis and de- scription. This methodology could serve as a novel way to investigate and describe the visual impact and benefi t of formulating effect pigments in cosmetic creams intended for application on the skin. INTRODUCTION Effect pigments are used in cosmetics for their ability to provide color, luster, iridescence, color travel, and texture. While metal-oxide-coated mica remains the dominant effect pigment technology in use for most color cosmetics, the past 20 years have seen the in- troduction of various new effect pigments that utilize novel transparent substrates such as synthetic fl uorphlogopite, borosilicate, and silica. Each of these substrates provides a range of optical properties that can deliver differentiated appearance and performance characteristics in cosmetic formulation. This abundance of choice creates a dilemma for the formulator that is looking for a comparative understanding of each technology when used in formulations where luster or radiance is desired. Address all correspondence to David Funk at firstname.lastname@example.org.
JOURNAL OF COSMETIC SCIENCE 190 Generally, white or clear skin care creams and lotions are not formulated with effect pig- ments, despite their value for increasing the appearance of luster and radiance on the skin. It is presumed that this is due to the desire of the formulator to avoid adding color or sparkle to the face. When effect pigments are used in these nondecorative skin care prod- ucts, the formulator requires an understanding of the visual benefi ts that the effect pig- ment might provide. To support the use of effect pigments in these skin care applications, there is an interest in developing methodology for assessing any impacts these pigments might have on radiance so that recommendations can be made for their use in this me- dium. Therefore, the purpose of this study is to develop a quantifi able method for deter- mining the radiance contribution from the use of effect pigments in a skin cream, and to use this method for the evaluation of various pearlescent effect pigment types. Included in this evaluation of radiance is the measurement of any color impacts on the skin from the use of effect pigments, primarily to help separate color contribution from lightness changes. Historically, skin tone drawdown cards have been used (1) as a screening tool to allow controlled colorimetric measurements of effect pigments over simulated skin color. This technique has been repeated in this study as a pre-experimental screening tool to deter- mine an effective pigment loading weight percent for luster on skin. Additional image analysis was then conducted on the coated skin tone cards to determine even coverage, correcting for the density and bulk densities for each substrate. In this study, we discuss the experimental results of an in vivo screening study intended to evaluate radiance and color measurements of various effect pigments in a simple skin cream. We evaluated various titanium dioxide (TiO2)-coated pearlescent effect pigments of a uniform color, particle size, and coverage, including TiO2-coated mica, TiO2-coated borosilicate, and TiO2-coated synthetic fl uorphlogopite, along with uncoated mica and bismuth oxychloride (BiOCl). A split-face in vivo study allowed the comparison of mea- surements of a skin cream containing no effect pigment, to various skin creams formu- lated with a uniform coverage of different types of effect pigments. Color measurements were taken via a handheld colorimeter to test for changes in the red/yellow appearance of the skin, while digital photographs of the volunteer’s hemiface were taken to allow image analysis for the determination of brightness. EXPERIMENTAL DEFINITIONS The terms “radiance” and “brilliance”, as representing the benefi ts of functional ingredients on skin (i.e., creams, pigments) have not been well defi ned by the industry (3). Recently, G. Martin-Langrand defi ned skin radiance as a subjective rating of individual parameters of the face, such as “luminosity of the complexion, homogeneousness of the complexion… , and contrast of the eye contour/whole face”, to defi ne overall skin radiance (4), whereas in the same publication, N. Lunau defi nes radiance as coming from a soft focus effect, “the so called soft focus effect, evens out the inhomogeneous aspects of the skin and leads to a more beautiful shine and radiance” (5). To better attempt classifying pigments and products us- ing these terms, there needs to be further research of the quantifi able adjustments needed to create radiance, along with the necessary methods to study this.
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