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© 1990 Society of Cosmetic Chemists
Journal of the Society of Cosmetic Chemists, Vol. 41, No. 2, 103-109


Physical sunscreens
Robert M. Sayre , Nikiforos Kollias , Richard L. Roberts , A. Baqer , I. Sadiq

ABSTRACT

Synopsis

Physical sunscreens have been described as compounds that attenuate radiation through scattering. This work indicates that physical sunscreens can be also strong absorbers of ultraviolet radiation as well as good scatterers of visible light. Compounds like barium sulfate and talc attenuate radiation at all visible and ultraviolet wavelengths only by scattering. Compounds like titanium dioxide and zinc oxide exhibit a semiconductor optical absorption gap, absorbing most radiation at shorter wavelengths than the gap, while at wavelengths longer than the gap these compounds scatter. Colored iron oxides scatter radiation and simultaneously absorb various visible and ultraviolet wavebands. This knowledge is important in the use of these compounds in sunscreen products because it suggests that while the scattering of a particle can be modified by its environment, the absorption characteristics of a particle cannot be changed.

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© 1990 Society of Cosmetic Chemists
Journal of the Society of Cosmetic Chemists