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Zinc oxide for a sunblock formulation
Would it be foolish & dangerous to use zinc oxide at 22% by mass in a lotion to make a sun block?
I have made it in the past, mixing 78% lotion with 22% zinc oxide (see zinc oxide description below). I would shake up the lotion before applying it and yes, it made me white, white, white. I did not get sunburns that summer, but THAT may have also been due to my not purposely lying around in the sun as I used to, AGES ago;).
Would a Z-cote micronized version of zinc oxide be more safe? Should that also be used at 22% by mass in a pre-made lotion?
Here’s the description of the zinc oxide, as described by the vendor, Saffire Blue:
Non-micronized Zinc Oxide is an inert non-organic product, insoluble in either oil or water, but rather will remain in suspension for long periods, however it will always, eventually ‘settle out’. Often used as a sunscreen and as a colourant in cosmetics and pharmaceuticals. Use at 1% to 5% in lotions etc.
The Zinc Oxide USP has a particle size of >99.99% passing through a 325 mesh sieve (44 microns). That means that more than 99.99 % of the particles will be smaller than 44 microns.
Zinc Oxide is used in cosmetics, as a pigment and a bulking agent (filler.) Commonly used in bath soaps, baby powders, diaper rash creams, baby lotions, ointments for burns, calamine lotion and mineral makeup applications. Zinc oxide soothes, protects and helps heal skin. Zinc Oxide is an anti-oxidant and can be used as a mild astringent and antiseptic to treat and relieve moist, painful and itchy skin conditions. It is commonly used in sunscreen formulations because it is able to absorb both UVA and UVB ultraviolet light.
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11 Replies
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No, zinc is completely safe.Are you mixing base lotion with 22% zinc? What’s the goal? Are you trying to achieve a certain SPF?My understanding is that with Z-Cote you can use a lower percentage to get the same SPF and less whitening but your lab can determine if you’ve got the SPF value you’re targeting. -
Yes, no problem. With micronized ZnO the white film will not be as obvious. You can also use a mixture of Titanium Oxide (7.5%) and Zinc Oxide (5%) which will give you an SPF of roughly 30 or just ZnO as you have done in the past.
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Aloha,
I am trying to achieve an SPF of 30.I looked on the label of a sunblock product, and they used 22% zinc by mass, THUS my adding the zinc to lotion I had prepared at 22%.I find purchased sunblock/sunscreen keeps me from sweating freely. I’m a sweater……. though some people say I’m actually more like a cardigan (insert laugh track here).I have no lab. I am the lab
. Mark Broussard: Did you mean titanium dioxide 7.5% and regular zinc oxide 5%?I can get MICRONIZED titanium dioxide (15 nanometers) or oil dispersible titanium dioxide. Which one is more effective for a lotion?Sorry for all the questions, people. I am a home formulator, not a professional cosmetic chemist, thus my ignorance. -
Micronized, in both cases. No point in spending extra money on oil dispersible if it costs more.
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Margreat, not sure if you are aware, but sunscreen is classed as a drug by the FDA.
Also, without a homogenizer how will you properly disperse the zinc? Zinc molecules are chemically inclined to clump together - visually you won’t see the clumping but you do not get an even spread of protection. The clumping leaves empty pockets and these “empty” pockets actually attract UV rays like a beacon risking skin damage - see: http://realizebeauty.wordpress.com/2012/12/30/the-trouble-with-making-your-own-sunscreen/ -
This is going to drive you crazy but:
how about if I use 5% of Z-cote oil soluble micronized zinc oxide & 7.5% regular oil soluble titanium dioxide in a prepared lotion?I CANNOT get the micronized titanium dioxide here in Canada, easily, it seems. I thought I could.Is the above % of minerals something you’d used commercially? (sorry if this is rude to ask)Thanks so much for the help. -
Yes, that works. Yes, you can find commercial formulations with the percentages of each ZnO and Ti02 referenced above.
As MakingSkincare noted above, without a homogenizer, you won’t get an even dispersion. You can add dispersion aids such as C12-15 Alkyl Benzoate to help. -
Thanks folks. I think I shan’t bother with trying to make a sunblock/sunscreen after all. After reading of zinc’s clumping properties, I’ll try to find another use for 800 or so grams of zinc oxide I have in a foil pouch.
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It makes a nice dusting powder mixed with talc or cornstarch…
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It can also be used at low levels to decrease the shininess (matte) of some emulsion bases, especially silicones.
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Hi,
I just found this old post and I would like to know what homogenizer could you propose for dispersing pigments and ZnO in a w/o emulsion?
For Zno, I’m currently using a pre-dispersed version (Zno in Caprylic/capric triglyceride) and I also use pigments to cover the whitening effect of ZnO. For ‘home-experimenting’, I’m using a simple homogenizer. The emulsion seems stable (but still under examination) and homogenous, however after applying it several days in a row, I experience comedogenicity. I’m wondering, could it be because the pigments (or Zno) haven’t been fully dispersed in the formula (or is it natural with this high level of Zno - around 20%)?
Thanks.
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