Thanks everyone! I'm about to order Ultra Sheer Zinc Powder and try it myself Thanks for help!

Hi! I was wondering if I could mix a sunscreen out of some powders like Ultra Sheer Zinc Finishing Powder, Pure Silk Powder and/or something else? Has anyone tried this? And what do you think the spf will be? I'm trying to achieve something like Bare Minerals' Mineral Veil spf 25 but it should be na...