As it can be seen in Fig 8 and in detail for selected sunsrceens (SPF 4 and 12) in Fig. 10, the absolute vale of also becase,according to what explained, the amount of back reflected radistion with respect to the transmitted radaition is very different. Besides there physical aspect related to surface/volume scatting of light,another fundamental event that can affect the result is the different chemical interraction of sunscreen with substrate materials. A further possible physical effect that can justify the differences is the fluorescence. The spectrophotometer used for our absorbance measurement has not filters on the input after the interating sphere to block out sunscreen product fluorescence. The could alter the adsorbance spectrum. In order to check for fluorescence effect,additional measurement of sunscreen absorbance have been performed by introducing different interferential filter between the sunscreen/substrate and the integration sphere. In all these cases the results were compatible with those obtained without the filter. This confirms that fluorescence does not after the measured absored value. Moreover,the chemical composition of the sunscreen tested has been analyed and no fluorescence ingredients have been found.