Our photostability can be conducted in two variations. The first variation is conducting the test based on the measured in vitro SPF, the second variation is conducted by assessing the test products ability to perform at a target in vivo SPF on human subjects. Photostability provides an evaluation of product stability and measures the UVA protection factor (UVAPF) and critical wavelength. Due to reflectance of some test product formats, in vitro results must be combined with in vivo SPF testing in order to obtain an accurate representation of the test product.
If you are interested in finding out how well a product will perform at a targeted SPF, the ISO24443 testing method is the best option for your product. This method will provide you with critical wavelength, and the UVAPF value. Testing both in vitro and in vivo for the most accurate results.
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