Formulating a sunscreen lotion with mineral UV filters.

DoreenDoreen Member
in Formulating

Hi,

I want to make a sunscreen lotion without other actives than the UV filters, for own use. The SPF will be about 15. The UV filters I use are micron. zinc- and titanium(di)oxide, coated with simethicone (SofiTix).
I also want to add another, volatile silicone, because of its nice skinfeel. I know silicones can be tricky, so I hope the stability of the way I formulated etc will be sufficient. This is the first time I will be working with silicones.

My formula, feel free to comment, much appreciated!

·         q.s. deionized water

·         8% E-wax (glyceryl stearate + PEG100 stearate)

·         2% cetyl alcohol

·         1% cyclopentasiloxane

·         9% sunflower seed oil

·         1% petrolatum

·         1.5% glycerin

·         0.5% α-tocopherol

·         6% SofiTix (nano zincoxide/nano titaniumdioxide/simethicone)

·         0.4% phenoxyethanol

·         0.3% benzyl alcohol + DHA (Cosgard)

·         0.1% potassium sorbate

·         citric acid in aqua for pH < 5.5


Phase 1:
Disperse SofiTix in mixture of sunflower oil + cyclo D5

Phase 2:
Water + glycerin, heat to 70C

Phase 3:
Melt the emulsifiers + petrolatum -> 70C

Add phase 1 to the 2+3 emulsion in the cooling phase.
Add preservatives + α-tocopherol.


QUERY: Would 9% oil be enough to disperse 6% SofiTix?
If so, should I use even less oil in the premix and add oil to phase 3?
Would this be stable enough for the 1% cycloD5 and the simethicone coating?

I wanted to add benzyl alcohol to prevent discoloration by potassium sorbate, like @DRBOB@VERDIENT.BIZ said. I don’t use it very long, so it probably won’t be necessary.
Is pH 5.5 low enough for potassium sorbate to ‘metabolize’ into sorbic acid?

Thanks a bunch!

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Comments

  • DRBOB@VERDIENT.BIZDRBOB@VERDIENT.BIZ Member
    yes 9% oil should be enough to dispese 6% Sofitix.Also  5.5 in low enough to form sorbic acid from Ksorbate which should be fine for preservation but will discolor with time however you use it up quickly.Why don't you raise Ph to 7-7.5 for optimum stability of Zn O and just use either BA or phenoxyethanol at  ! % ?

  • DoreenDoreen Member
    edited June 2017
    @DRBOB@VERDIENT.BIZ
    I didn't know the optimum stability of ZnO being so high? And what about the TiO2?
    Will it really be a problem to put it at 5.5? If it is necessary, I'll raise the pH with Na lactate and get rid of the phenoxy and potassium sorbate (which isn't stable then I assume) and just do the Cosgard (BA +DHA).
    Or just phenoxyethanol alone? :)
  • DRBOB@VERDIENT.BIZDRBOB@VERDIENT.BIZ Member
    Below 7 Zno forms Zn++ ions which raises issues of stability/efficacy so we always keep our mineral sunscreens above 7:  At 7 K sorbate doesn't work but you can use either BA or Phenoxyethanol at 1%.  















  • DoreenDoreen Member
    edited June 2017
    Edit:  message deleted, question is answered above.
  • DoreenDoreen Member
    @DRBOB@VERDIENT.BIZ
    At 7 K sorbate doesn't work but you can use either BA or Phenoxyethanol at 1%. 
    Does that mean I don't need additional antifungal excipients at pH7 or >7?
  • DRBOB@VERDIENT.BIZDRBOB@VERDIENT.BIZ Member
    no  you should be fine
  • DoreenDoreen Member
    @zwapp
    Thanks for the reminder, you're right! I've got tocopherol acetate aswell, so that's not a problem. Or I just leave it out, both.
  • pradeeppradeep Member
    I have heard if titanium di oxide is inhaled during preparation it may be carcinogenic itself. So does it necessary to use in spf lotion Or what is the safe method of handling tio2.
  • DoreenDoreen Member
    @pradeep
    Lots of chemicals have inhaling hazards, even cellulose or niacinamide. Take adequate safety measures all the time (ventilation etc). If you handle powders a lot, you can think of using simple dust-masks.

    For this lotion I have chosen a combination of TiO2 and ZnO, both are broad spectrum.
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