Hallstar Clear Stick Deodorant

Hi all,

I'm following this formulation, and modifying it using sodium laurate\stearate derived from coconut oil and sodium hydroxide:
https://www.hallstarbeauty.com/formula/clear-glycerin-based-deodorant-stick-2/

And then also following bobzchemist's instructions here:

https://chemistscorner.com/cosmeticsciencetalk/discussion/947/making-deodarant

Specifically this post:

"If you're trying to make a solid stick, it would probably be easier to use Sodium Hydroxide and Stearic Acid. Heat your water/zemea mixture to no more than 85C, start stirring, add Stearic Acid, wait until it's dissolved, add Sodium Hydroxide, mix 30 minutes while reaction completes, (it's exothermic, so you will probably shoot up to 95C without heating further. If your starting water mixture is too hot, the extra heat from the reaction will make the batch boil - not a good thing) Add your other ingredients and cool down. Pour into sticks at about 60 - 70C"

As I'm following the Hallstar formula that uses glycerin instead of glycol, I mix that and the water together, heat it up, add the coconut oil, wait for that to dissolve, then add the sodium hydroxide.

Here are the amounts I'm using (in grams) aiming for 50 grams of deodorant:
Glycerin37.57
Water8.60
Coconut Oil
Sodium Hydroxide
3.27
0.56

The problems I'm running into are:

1) My hot plate\magnetic stirrer takes a long time to come up to temperature and struggles to get beyond 60C. Does bringing glycerin up to 80C do something to its structure?
2) This is still very liquidy after cooling
3) The amount of coconut oil and sodium hydroxide seem like what's needed to create the proper amount of sodium stearate (and sodium laurate) to act as a gellant for the deodorant according to the formula, but that really doesn't seem like "enough".

Eventually, once I solve the solidification issue, I'd like to add zinc oxide, magnesium hydroxide, and zinc ricinoleate to the mix - will I need to adjust anything, or can I just add all three of those at the end (and increase total volume) without issue?

Thanks in advance for any feedback and\or guidance!

Comments

  • Coconut oil is not 100% Stearic Acid.

    This is basic stoichiometry. Coconut oil is made of triglycerides (3 fatty acids attached to a glycerin). Only about 1-3% of all the fatty acids in coconut oil is stearic acid https://www.sciencedirect.com/topics/neuroscience/coconut-oil

    To achieve 6.5% Stearic Acid in your formula would would need to divide the percentage required over the actual concentration of that fatty acid in your oil: (6.5%/0.01 to 6.5%/0.03) so you need between 216% to 650% coconut oil to achieve a final 6.5% stearic acid concentration (not even considering the excess that you would need to add to account for the glycerin byproduct from the oils). Long story short, it’s impossible. If you make soap (just oils and lye and let it cure for water to evaporate) the maximum Sodium Stearate in your soap will be less than 3%.
  • cdluckcdluck Member
    Hi @letsalcido!

    Thanks for the reply! Considering lauric acid is the dominant fatty acid in coconut oil, is sodium laurate not a sufficient substitute as a gellant? Or does the lauric acid become something else entirely in the presence of glycerin?
  • BelassiBelassi Member
    Considering lauric acid is the dominant fatty acid in coconut oil, is sodium laurate not a sufficient substitute as a gellant?
    Why are you asking us, considering that you have just conducted a chemistry experiment that answered your question? As far as this is concerned you now know a lot more than I do about it.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • PharmaPharma Member, Pharmacist
    edited May 26
    Unlikely that sodium laurate will work. Nope, just putting lauric acid and glycerol in the same pot gives just a pot filled with lauric acid and glycerol.
    If you need a plan B, you could try glyceryl stearate or glyceryl palmitate... if you happen to have that in stock. Though, I do think it's not going to be transparent.
    EDIT: And if you had berry wax in stock... that's mostly palmitic and stearic acid ;) .
  • cdluckcdluck Member
    Belassi said:
    Considering lauric acid is the dominant fatty acid in coconut oil, is sodium laurate not a sufficient substitute as a gellant?
    Why are you asking us, considering that you have just conducted a chemistry experiment that answered your question? As far as this is concerned you now know a lot more than I do about it.
    Haha, duly noted - I asked because I wasn't sure if I managed to screw things up by not attempting to saponify the coconut oil before adding the glycerol to it first, thereby causing what @Pharma said about just having a pot of lauric acid and glycerol.

    I tried searching for differences in sodium laurate and sodium stearate, but couldn't find very much. People seem to make solid soap out of both, but stearate is the one found in deodorants, and I couldn't tell why.

    @Pharma - Thanks for the response! So if lauric acid and glycerol are in the same pot, adding sodium hydroxide won't saponify that acid? Is that lye still just floating around in the liquid at this point?

    Thanks again everyone, I appreciate the feedback!
  • PharmaPharma Member, Pharmacist
    Nope, hydroxide will easily react with the acid turning it into sodium laurate. But it behaves differently than sodium stearate which forms a unique kind of crystals stabilising/gelling oil.
  • cdluckcdluck Member
    @Pharma Thank you for the explanation - that's the sanity check I needed! :smile:
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