Table 1. Active filters in the 11 test products

Regarding the test procedure, 28.7 mg of each product was dispensed and spread carefully over the PMMA plate. The samples were allowed to settle for 15 min in the dark at room temperature to ensure leveling of the products. A total of nine UV transmission spectra—i.e., from 290 to 400 nm, in 1-nm increments—were recorded at different locations on each plate. A transmittance analyzer was then used to determine the diffuse transmission spectrum of UV radiation through the substrate before and after irradiation, followed by the photostability percentage.