Now that I’ve discussed sunscreen actives, here is an example of a basic formula for a sunscreen emulsion. This formula is taken from the ChemistsCorner website which I highly recommend that you read if you aren’t already! It is a great source of cosmetic science information.
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| Image: ChemistsCorner |
Sunscreens can also be anhydrous, in a spray form, and a stick form.
To figure out how much sunscreen actives you will need to reach your desired SPF, here are some GENERAL guidelines:
Organic sunscreens generally provide 2 SPF units per percentage of organic sunscreen active.
Titanium dioxide generally provides 2-3 SPF units per percentage of TiO2. You will get less SPF units if you have TiO2 with large particle size.
Zinc Oxide generally provides 0.5 to 2 SPF units per percentage of Zinc Oxide, depending on particle size.
Also keep in mind when estimating SPF:
1) There is synergy among TiO2 and ZnO and organic sunscreen actives
2) SPF boosters can help boost SPF
3) Other formula ingredients can help maximize SPF: film formers help keep sunscreen on the skin
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