• Formulating

  Sunscreens and spf

  Posted by Stanley on July 20, 2021 at 8:55 pm

   Is there a ratio  of how much ZnO to achieve a SPF? 

  I read the following from a website: Zinc Oxide Can be added to formulas as is, recommended concentration: 5-25% (10%
  corresponds to a SPF of about 6-11).  I am confused somewhat…..

  Stanley replied 3 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  gordof

  Member

  July 23, 2021 at 7:29 am

  Hi Stanley 

  For ZnO and SPF, it is somehow tricky it depends a lot on the Grade of ZnO you are using for the formulation what kind of Spf you really get as well as on the Formulation and the distribution habits for the ZnO. 

  but there are some helpers out there you can Register for example on the https://www.sunscreen-optimizer.com/

  there you can find ZnO as an ingredient and you can add different amounts of it and see how the estimated SPF value will be. 

  the results are quite good but due to the fact that especially with a mineral Sunscreen filter the distribution on the skin is a major factor for SPF, and that is influenced by your formulation a lot, you will need to try it in a test 

  there is a regulatory maximum you are allowed to use (at least in Europe) that is 25 % the estimated SPF for a cream with 25 % ZnO would be around 15 -16. 

  I hope that answers your questions and helps you.

  Tobias

• 

  Stanley

  Member

  July 23, 2021 at 10:38 pm

  @tobias
  thank you so much!!! this does help alot!!!

Log In to Reply