ENHANCING SKIN RADIANCE THROUGH THE USE OF EFFECT PIGMENTS 193 in the formula would result in far fewer particles upon skin application than any of the other products and therefore a weaker coverage on the skin. Product D also has a slightly lower density and a higher particle size compared to the other products, resulting in a different coverage property compared to the other products. A simple technique was developed to measure the coverage of the various products using optical micrographs. Products B, D, and E were put in a nitrocellulose lacquer base (75% solvent) at various concentrations. Product A was ignored since it would not readily ap- pear visible in the lacquer solution, and Product C was ignored since is it very similar to Product B. The lacquer solutions were spread across black drawdown cards at a fi xed speed using a stainless steel 3 mil wet fi lm bird applicator (Paul N. Gardner Co., Inc., Pompano Beach, FL). The drawdown fi lms were then left to dry, after which optical micro- graphs of the fi lms were taken. Three images at 700× magnifi cation at random locations on the card of the various products and concentrations were taken (Figure 2). Image analyses of the micrographs were carried out using ImageJ software (version 1.48, NIH, Bethesda, MD). The micrographs were contrasted equally and the area of black background was calculated. The area of the background was subtracted from the total area and the percent of coverage was determined and shown in Figure 3. Figure 3. Coverage of the products at various wet concentrations. Figure 2. Sample Micrographs of the Concentration Films Used to Determine Coverage

JOURNAL OF COSMETIC SCIENCE 194 This simple technique shows that the Products D and E should be double the con- centration in the formula to show equal coverage and a fair comparison of the prod- ucts. For the study, 2.5% was chosen to the baseline formula concentration, which is a common concentration for skin creams and lotions, and doubled to 5% for Products D and E. IN VITRO: SIMULATION OF RADIANCE ON SIMULATED SKIN COLOR As a simple laboratory simulation to attempt to quantify the brightening benefi ts of these effect pigments, nitrocellulose fi lms of these products incorporating 2.5% and 5% of pig- ment by wet fi lm weight were prepared on skin tone color charts for color analysis. This novel color chart was developed by The Leneta Company (Mahwah, NJ), in 2001, according to our specifi cations based on CIELab values to simulate increasing skin tone colors, and is used as a simple screening tool to help characterize visual interactions of effect pig- ments on skin (Figure 4). A 3-mil Bird Film Applicator drawdown bar was used to drawdown the samples at a steady rate on the Leneta Skin Tone Color Chart. Product A was ignored since its impact would be negligible once placed in formulation. The nitrocellulose fi lms were set to dry at room temperature for 24 h. Colorimetric measurements using a multiangle spectro- photometer (BYKMac 12mm, BYK-Gardner GmbH, Geretsried Germany) were taken. To simplify the analysis, only the data for layer 2, light beige (L*a*b* = 78, 7.25, 14.8) was collected. The +25º off the specular refl ection measurements were reviewed, representing the second strongest pearlescent angle for the spectrophotometer, referred to as the “fl ash” angle (ASTM E284-13b), representing the light that is redirected off the specular refl ection. Figure 5 shows that the application of each of the four effect pigment types over the skin tone card reduces the a* and b* parameters of the skin tone, effectively acting to diminish the red and yellow appearance of the skin tone. Figure 6 shows that each of the products increases the L* parameter compared to the normal skin tone color. To simplify the re- sults, Figure 7 shows both the change in chroma and the change in lightness of each of the products compared to the skin tone color. These dL* and dC* values show the Figure 4. Leneta skin tone color chart (1) white, (2) light beige, (3) dark beige, (4) yellow-beige, (5) light brown, (6) dark brown, (7) black.