SUNSCREEN TESTING METHODS .?-' : .? • :. . .. }•: .:: .• :! ::, - " . ::!4: .... --.. -'.. . . -:-.."- :: .. ....... } :... --. .... .: :• UNEVEN SPREADING Figure 7. Plates showing uneven spreading of substatices 815 Table II Ranked Differences in Protection Achieved by Ten Sunscreens and Controls Comparing Natural and Artificial Light Using the Photographic Technique Natural Sunlight Artificial Sunlight Burdick UV 800 (Quartz Mercury Con- Sun- Vapor Lamp) trol screen Read- Read- Differ- Differ- Sunscreen" ing ing ence Rank ence Rank Solbar--hydroxy and dihydroxy 1.00 0.04 0.96 1 1.00 1 methoxybenzophenone Afil--menthylanthranilate, 1.10 0.56 0.54 2 0.52 2 titanium oxide RVPaque--zinc oxide, red petro- 1.10 0.62 0.48 3 0.45 3 latum, ethoxyethyl p-methoxy- cinnmnate RVPlus--red petrolatum and 1.30 1.05 0.25 4 0.19 5 titanium coated mica particles Army Mixture--ethoxyethyl-p- 1.00 0.78 0.22 5 0.22 4 methoxycinnamate in silicone and castor wax Shade Coppertone--homomenthyl 1.20 1.00 0.20 6 0.15 7 salicylate and lanolin Neo-Afil--digalloyltrioleate 0.94 0.79 0.15 7 0.13 8 Sea & Ski--glyceryl p-aminoben- 0.98 0.86 0.12 8 0.12 9 zoate RVP--red petrolatum 0.95 0.84 0.11 9 0.18 6 UVAL--hydroxy, methoxybenzo- 1.30 1.20 0.10 10 0.11 10 phenone and sulfonic acid Ranked evaluation of ten sunscreens 5 mg/0.78 cm 2b "See footnote in Table III for trade name information. • Averaged result of multiple tests. The probability that such an agreement of rankings could have .•' esulted from chatice alone is less than 1% (Spearman Rank Correlation Coefficient Test).

816 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS G!yc Para:-.,--•"•' Sea:: & Ski .86 c .98 •:•. R :V P C Ont ::• .,84 .:95 Figure 8. Test substances and control. achieved. Differences in density correspond to protection Peripheral gray halo is artifactual since the assembly ports could not be made "light-tight" without scratching the film plate The plates are developed for 30 seconds at 24øC in normal developing solution, fixed, washed, and air dried. The short development time precludes overdevelopment of either the control or experiment. The degree of blackening of the plate of the sunscreen-protected area is measured with a Densichron densitometer and compared with that of the control area (Fig. 8). As expected, protected areas are less dark than