CHALLENGES TO SUNSCREEN EVALUATION 593 (B) Experimental sunscreen P (Table IV) • Technical data: pH = 4.75-5.75 viscosity (Brookfi eld DV II + T-D @ 3rpm) = 20,000– 45,000 cps. • Manufacturing procedure: In a suitable container with an appropriate mixer, ingredi- ents in Part A are added and heated to 68°C–73°C. In a side container, ingredients of Part B are mixed and heated to 68°C–73°C. When Parts A and B are at the indicated temperature, Part B is slowly added into part A and mixed well and/or milled if de- sired. In a side container, ingredients of Part C are blended until uniform. When the main batch is below 50°C, Part C is added and mixed well. Cooling of the batch con- tinues. When the main batch is below 30°C, Part D is added and mixed well until it is completely smooth and uniform. Ingredients of part E are preblended, added to the main batch, and mixed well. The rest of the ingredients are added separately and mixed until uniform. EXPERIMENTAL RESULTS AND DISCUSSION Experimental data are presented in Figures 3-4 and Tables III-V. Figure 3 illustrates poten- tial limitations of the proposed roughened quartz substrate that are apparent even for SPF Table IV Experimental Sunscreen P Part INCI-Name/USAN Supplier % w/w (as supplied) A Water q.s Disodium EDTA Fluka 0.10 PEG-8 Jeen International 1.00 Butylene glycol Fluka 2.40 B Dibutyl adipate Cognis 3.00 Steareth-20 Lipo 0.80 Steareth-2 Lipo 0.50 Isodecyl neopentanoate ISP 2.00 PEG-100 stearate Lipo 2.55 Bemotrizinole (USAN) Ciba 2.30 Octocrylene ISP 2.00 Avobenzone DSM Nutritional Products, Inc. 3.00 C12-15 alkyl benzoate Finitex 2.50 Isononyl isononanoate Alzo International Inc. 2.00 Cetyl lactate Lipo 0.75 Diethylhexyl 2,6-naphthalate Symrise 1.75 Isopropyl myristate Cognis 1.60 C Water 20.00 Bisoctrizole (USAN) Ciba 7.00 Acrylates/C12-22 alkylmethacrylate copolymer ISP 1.00 D Sodium acrylates copolymer (and) hydrogenated polydecene (and) PPG-1 trideceth-6 Ciba 1.00 E Cyclopentasiloxane (and) dimethiconol Dow Corning 0.90 Isododecane and dimethicone crosspolymer-3 Jeen International 0.50 F Phenoxyethanol (and) ethylhexylglycerin S&M 0.80 Fragrance q.s

JOURNAL OF COSMETIC SCIENCE 594 30 sunscreen, with its absorbance spectrum being close to the dynamic range limits of the transmittance analyzer. These limitations prohibit the evaluation of high SPF sunscreens on a roughened quartz substrate. The utilization of the roughened quartz substrate also creates the following technical problems: CV values were much higher than the required 10% or less for all tested products due to the lack of uniformity. An alternative substrate, Vitro Skin® N-19, worked well with the application dose recommended by the FDA however, it was found that the application time of ten seconds was not suffi cient to evenly apply the sunscreen over a relatively large application area. Thirty seconds of application time seems more reasonable in conjunction with this substrate. It was possible to obtain CV values of 10% or less on the alternative substrate. The surface of Vitro Skin® N-19 is more effi cient in de-emulsifying sunscreen emulsions and supporting low spot-to-spot variability during the transmittance measurements compared to the roughened quartz plates proposed by the Figure 3. Absorbance spectra of experimental sunscreen P (SPF~30) with “highest” UVA rating (Labsphere UV 2000S Vitro Skin® N-19 Q-Glass). Figure 4. Absorbance spectra of test articles after irradiation (Labsphere UV 2000S Vitro Skin® N-19).