266 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS use. Typically, color DE values greater than 1.0 indicate visually perceptible differences between two samples. Due to the high reflectivity and chroma of pearlescent effect pigments and applications incorporating them, the use of DE = 1.0 as a visually perceptible difference between two samples may not be applicable, especially near the specular reflection angle. It may be more applicable in these cases to use the DEc•tc n parameter to define visually perceptible differences. FINAL COMMENTS With judicious choice of sample form and instrumentation, the instrumental measure- ment of pearlescent samples is possible for use in controlling raw material and final product quality. Proper application of the measurement information requires relating the measured attributes with the visual perception of the sample, without which the data is useless. However, even when appropriate cautions are observed, the instrumental measurement of the appearance and color of pearlescent pigmented materials may de- viate from visual assessments. Contributions due to sparkle or glitter effects may require additional instrumentation to evaluation in a non-subjective manner. Quantification of the performance of a range of surface treatments JANE HOLLENBERG, JCH Consulting, DREW SUJET, Cardre, and M. SCOTT PRICE, Cardre. INTRODUCTION Surface-treated pigments and fillers were originally utilized in industrial coatings to improve wetting, reduce reactivity of the pigments with the vehicles, or to couple the finished coating to the substrate. The first surface treatment to be used for cosmetic applications was polymethylhydrogensiloxane (INCI name: methicone) for the purpose of rendering pigments and fillers hydrophobic, thus improving wear. Since the intro- duction of cosmetic-grade methicone-coated pigments to the United States from Japan in the early 1980s, the number of available treatments has proliferated. Although excellent reviews of cosmetic pigment treatments are available (1,2), a quantitative, comparative study of the properties of the various treatments related to performance attributes has not been published. We have used objective, reproducible test methods to obtain data to guide cosmetic chemists in their choice of surface treatment. The treatments tested were chosen for their frequency of use and the functionality they are expected to impart to the pigments and fillers.

PREPRINTS OF THE 1996 ANNUAL SCIENTIFIC MEETING 267 Treatments evaluated were N-lauroyl lysine, lecithin, metal soap, methicone, polyeth- ylene, silane, and unreacted perfiuoro compound. TEST METHODS COMPRESSIBILITY A simple pressed powder formulation (Table I) was chosen to measure resistance to breakage by a drop test. The only variation was in the type of treatment on the talc the other powders were untreated. Conditions: 5 g powder/43 mm pan/pressure 2000 psi. Five samples were dropped from a height of 27 cm onto a lab bench until broken. The number of drops represents the number prior to breakage. Subjective properties such as pick-up, application, skin feel, glazing, and dusting were also noted. All treatments provide an improvement in compressibility over untreated talc, without compromising application (Figure 1). The effect would be more pronounced if all raw materials were treated, not just the talc. The control formula dusts excessively, as do the versions containing talc treated with lauroyl lysine and methicone. Lecithin treatment gives the smoothest, moistest skin feel, with metal soap treatment a close second. Silane treatment is the most effective in increasing the strength of the pressed cake, and so would be recommended for materials that are difficult to compress. HYDROPHOBICITY Eight milligrams of specified concentrations of a methanol/water mixture were measured into centrifuge test tubes. Three tenths of a gram of treated pigmentary titanium dioxide were added. The tubes were agitated by rolling for thirty seconds, then cen- trifuged for five minutes at 3000 rpm. The sediment volume was measured, reported as percent total pigment volume, and plotted against the methanol content (Figure 2). The greater the methanol content without settling, the more nonpolar ("hydrophobic") the coating. The titanium dioxides coated with methicone and with silane are the most hydrophobic, and so would be recommended for formulations in which waterproofness is a desired property. Because both are covalently bound to the pigment surface, they can be utilized in dispersed systems, including emulsions and anhydrous formulations, without concern Table I Pressed Powder Formulation Talc (treated) Mica ( 15 Zinc Stearate Titanium Dioxide Iron Oxides Methyl Paraben Propyl Paraben Caprylic/Capric Triglyceride 55.40 30.00 3.00 5.60 2.70 0.20 0.10 3.00 100.00