Question about Iron Oxide as Sunscreen

mcarsmcars Member
Is there any minimum concentration of iron oxide to exhibit UV protection?
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Comments

  • johnbjohnb Member, Professional Chemist
    edited March 2017
    Are you sure you want to use iron oxides for this purpose?

    All grades of iron oxide are strongly coloured. Any amount applied to the skin will be visible and possibly/probably unwanted.

    Think carefuly about user acceptibility before you proceed much further.

    Regarding the specifics of your question, I doubt that anyone has investigated the spectrum absorbing qualities of iron oxides for the end uses you intend.
  • JulietKJulietK Member
    edited March 2017
    @mcars

    Maybe what you mean is zinc oxide?
    Or titanium dioxide?
  • BobzchemistBobzchemist Member, PCF student
    Also, Iron Oxides, due to their color, will likely heat up in intense sunlight. I can't imagine that this would be pleasant.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • mcarsmcars Member
    i was just planning to add iron oxide for aesthetic purposes as coloring pigment and I was just curious of the minimum conc for protection against visible light
  • BobzchemistBobzchemist Member, PCF student
    Back when I was working on formulating standard liquid foundations, we tested all of them for SPF, to see if we could make any claims. Most of the regular coverage formulas had a SPF of 2, the others were zero. All tinted moisturizers tested were zero. High coverage formulas and concealers got about a 4. The SPF results correlated well with the TiO2 levels - iron oxide levels had virtually no contribution to SPF at all.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • PerryPerry Administrator, Professional Chemist
    edited March 2017
    Visible light isn't the problem that sunscreens are solving. SPF is a measure of how well a product protects against UV light.

    Iron oxides also aren't on the FDA's list of sunscreen actives.
    http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=352.10
  • WHY not use a mixture of ZnO and TiO2 which are approved.Critical wavelength for UVA (370nm) is easily achieved using relatively low levels of the combination?
  • BobzchemistBobzchemist Member, PCF student
    Perry and Dr. Bob both have a good point. Since even mentioning anywhere that your SPF coverage had anything to do with iron oxides could result in the FDA forcing a recall of your product, why  would you bother?
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
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