Troubleshooting - magnesium stearate

Hello all. This is my first post and I am not a professional formulator - I am a DIYer so please have patience :) I am trying to develop a *natural* vegan cream foundation. What I have so far is a medium-coverage (by industry standards) anhydrous cream foundation in a balm form. After it is applied it looks amazing on the skin, looks like skin, lasts for at least 8 hours and feels weightless on the skin. The problem is, in the pot it feels super sticky and tacky, and after two weeks it develops a skin on top (ew). You can rub the surface and break the skin to get to the rest of the product, but this feels gross. :/ I think the problem is the magnesium stearate that was added for slip and adhesion. Without it, the formula does not last on the skin as well and easily rubs off.

My formula is:
25% pigments (oxides and TiO2 blend)
45% plant oil blend (sunflower, argan, jojoba)
10% carnauba wax
10% magnesium stearate
5% cornstarch
1% vit E

Now, I have searched through Google exhaustively on information on magnesium stearate and I have found no mention of something like this.

Comments

  • Do a knockout starting with C-wax.What is your process?
  • BobzchemistBobzchemist Member, PCF student
    Under what criteria are you considering the Magnesium Stearate "natural"?

    What grade of Magnesium Stearate are you using?

    What temperature are you heating your batch to?
    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
    Here is what @DRBOB@VERDIENT.BIZ means by a knock-out experiment.  
    https://chemistscorner.com/do-you-know-the-fastest-way-to-become-an-expert-cosmetic-formulator/

    Essentially, you make a series of batches leaving out one ingredient. Then you see what happens to the final formula.

    I would think the Plant Oil would be your "solvent"


  • Bobzchemist Thanks for commenting!

    *natural* is a funny word, isn't it? LOL Basically, I see *natural* makeup products with MgSter or Zn stearate etc, so I'm using that criteria.

    "What grade of Magnesium Stearate are you using?" I did not know there were different grades. I guess I would say I acquired some pharmaceutical grade MS? I am in Brazil and here it is possible to buy some formulating ingredients from pharmacies in small quantities.

    "What temperature are you heating your batch to?" around 200F since MS has a high melting point.
  • bellbottombellbottom Member
    edited June 2017
    @Perry thanks for commenting! I watch all your videos and it is a pleasure to "speak" to you!
    @DRBOB@VERDIENT.BIZ thanks for the tip!

    I will try the knockout experiment for sure! At least, I will try without the c-wax, since I have already tried removing the MS and the makeup did not last on the skin at all. I have also tried without corn starch but it feels too oily on the skin. (I would love to use silica instead of the starch for oil absorption but I cannot buy that here in Brazil.) One thing I plan on doing next is also to decrease the MS to 5% and then adjust the formula accordingly.

    The process I use is: I melt the MS over direct heat as it does not melt in Bain-Marie (melting point is around 200F) with my vegetable oils. As soon as it is melted (solution is not cloudy) I add the C-wax. When that is melted, I incorporate the powders and I do a little dance called "remove from heat and stir like crazy and then place over heat again and stir some more and repeat ad nauseam" until it is all incorporated. One super fun part of this is when the powders, specifically the corn starch, is added, the MS BUBBLES UP like crazy (hence the remove from heat part). Finally when all the bubbles are gone and everything is melted/incorporated I pour the rapidly solidifying goop into a container. 
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