814 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 2.0 D--O.1 Above Gross Fog -- . -- Z 0.0 u• o I 2500 3500 4500 5500 WAVE LENGTHS IN ANGSTROMS Figure 6. Spectral sensitivity of medium contrast Kodak projector plates The measurements to be described have been made within two hours of noon at an altitude of 5,280 feet (1600 meters) on cloudless, haze- less, summer days. Ultraviolet light is measured with a J-221 meter.* Each experiment and its control have been performed in light of equal intensity as measured by this meter. A 5-mg mass of each sunscreen (Table II) is placed on a quartz glass slide and spread evenly over an area of 0.8 cm 2 by pressing with a cover- ing glass quartz slide. Quartz glass is used because it transmits the ultraviolet light found in our atmosphere. Substances which do not spread uniformly registered irregular densities on the developed film plate. These plates are discarded (Fig. 7) even though such irregular- ities are not always visible on the quartz slides. The slides carrying the sun protectant are placed over the filter, the portable shutter is cocked and placed over the slides, and the film pro- tector is removed. The complete assembly is then pointed directly toward the sun and the shutter is released, thus exposing the film under one port. The film protector is replaced and the procedure is repeated at the next port without the sunscreen as a control in the same sunlight. An equal amount of each sunscreening agent is tested in two ways: (a) in the sun, and (b) with a Burdick UV 800 quartz mercury vapor lamp, t maximum output of which is in the sunburn area. * Ultraviolet Projects, San Gabrid, Calif. } Burdick Corporation, Milton, Wis.

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).