I am young cosmetic formulator and I have difficulties determining the SPF factor ot my formulas (mainly Emulsions). I use Spectrophotometer and relevant software (OptLab5). The problem is there, that even with small amount of UV Filters (for example 5% Ethylhexyl Salicylate, 5% BMDM and 5% Tinosorb S) the software gives me result like 99.0/99.0 for SPF/UVAPF (Colipa 2009). When I use the BASF Sunscreen Simulator and run simulation with the exact same amount of filters, it shows me SPF 20. I want to know how to reliably determine the SPF of my products, is it SPF 20 or SPF 50+ for example? Can someone with experience using similar methods help me, please?
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