chapter  44
20 Pages

Prediction of Sun Protection Factors of Inhomogenous Surface Structure

Introduction 882

Materials and Methods 883

UV Filters and Formulations 883

Measurement of UV Spectra 884

Measurement of UV-A Parameters 885

Introduction of Step Film Inhomogeneity by Mathematical Models 885

Calculation of Average UV Spectra from the Spectra of Individual

UV Filters 885

The Step Film Model by O’Neill 886

Using a Distribution Function for Introduction of Film Inhomogeneity 889

Correlation of Experimental and Calculated Data 891

Calculated SPF and SPF In Vivo 891

Correlation of Calculated UV-A Parameters and UV-A Parameters

Measured In Vitro 895

Summary 899

References 899


The measure of the protection against sunburn achieved by application of

sunscreens is the sun protection factor (SPF). The SPF is defined as the ratio

of the minimal erythemal doses of solar radiation directed to human skin in the

presence and in the absence of a sunscreen (1).