natural deodorant emulsion problem

Hi, I´m a chemist from Mx, graduated Dec 2018

During first weeks of pandemic I started a personal project to lower stress and do something productive

I started doing experiments to create a natural deodorant stick (aluminum free)  but had several problems. I have tried SOO many ingredients and formulations and I have some that have potential... basically some surfactants, oils, waxes, fragance and active ingredients

Problem is I would like it to be an emulsion, so I could dissolve my active ingredients (mainly pH modifiers, very acidic OR very alkaline) and have a fresh feel on the skin but Im having stability problems.

One of my best formulas consists of W/O emulsion with low HLB solid emulsifier (sorbitan stearate) coupled with a little bit of high HLB surfactant (lauryl glucoside)... blends well while melted but when I pour it in the container to solidify the top has a lot of foam and after 3-4 days theres a lot of syneresis

Could someone give me some advice to increase stability? I only have access to a simple stirring/heating plate

Should I go with a water based emulsion instead?

surfactant suggestions that are easy to find and not petroleum based, and not ethoxilated? I tried ceteareth and worked very well, but consumers wont consider it a "clean" ingredient bc of dioxane

finally does anyone know a database with required HLB values for both types of emulsions?? 

Comments

  • PerryPerry Administrator, Professional Chemist
    To get helpful answers you should list specifically what is in your formula.
  • @natiyo123 I’m also newish to formulating, and have slowly come to learn that w/o are a pain in the butt.

    If you’re not married to the idea of making the deodorant as a W/O or O/W emulsion (not sure how o/w would work as a bar...) you can go the anhydrous way.

    I make my own deodorant with Propylene Glycol and 3-5% Sodium Stearate. This will create a clear bar, and you can use that as a vehicle for your actives and build upon it. You can use lauryl glucoside to incorporate some oil into the bar as well, if you’d like a more emollient feel. It would also probably be cheaper than using waxes and oils. This is a super common formula/base for deo sticks.

    You should also be able to use water and PG for the same bar formulation, but I haven’t experimented to see what the ratio should be so it is stable and doesn’t “sweat”. PG is cheap so I’m not worried about using that only.

    Otherwise, like Perry mentioned, it would be best if you can share your full formula.
  • natiyo123natiyo123 Member
    Perry said:
    To get helpful answers you should list specifically what is in your formula.
    o Sorbitan Stearate
    cetyl alcohol
    caprylic/capric triglycerides
    water
    castor oil
    fragance
    rice wax
    lauryl glucoside
    citric acid

  • natiyo123natiyo123 Member
    @natiyo123 I’m also newish to formulating, and have slowly come to learn that w/o are a pain in the butt.

    If you’re not married to the idea of making the deodorant as a W/O or O/W emulsion (not sure how o/w would work as a bar...) you can go the anhydrous way.

    I make my own deodorant with Propylene Glycol and 3-5% Sodium Stearate. This will create a clear bar, and you can use that as a vehicle for your actives and build upon it. You can use lauryl glucoside to incorporate some oil into the bar as well, if you’d like a more emollient feel. It would also probably be cheaper than using waxes and oils. This is a super common formula/base for deo sticks.

    You should also be able to use water and PG for the same bar formulation, but I haven’t experimented to see what the ratio should be so it is stable and doesn’t “sweat”. PG is cheap so I’m not worried about using that only.

    Otherwise, like Perry mentioned, it would be best if you can share your full formula.
    Thanks for the suggestions, yes I have tried sodium stearate too, I tried to recreate TOM´s natural deodorant at one point, I will definitely keep this in mind.  
  • EVchemEVchem Member
    W/o usually requires homogenizing so with just a stir plate I don't think that route will work for you
  • You can add Tribehenin to combat syneresis 
    Dr. Catherine Pratt
    (B.Sc with HONS I , Ph.D Analytical/Organic Chem and Microbiology), Cosmetic Chemistry IPCS)
  • EVchem said:
    W/o usually requires homogenizing so with just a stir plate I don't think that route will work for you
    yeah I imagined, smaller droplets would increase stability... Cant do that at this moment, maybe Ill have to get rid of the water all together 
  • You can add Tribehenin to combat syneresis 
    thanks for the suggestion... I see its structure is quite interesting!
  • @natiyo123 I’m also newish to formulating, and have slowly come to learn that w/o are a pain in the butt.

    If you’re not married to the idea of making the deodorant as a W/O or O/W emulsion (not sure how o/w would work as a bar...) you can go the anhydrous way.

    I make my own deodorant with Propylene Glycol and 3-5% Sodium Stearate. This will create a clear bar, and you can use that as a vehicle for your actives and build upon it. You can use lauryl glucoside to incorporate some oil into the bar as well, if you’d like a more emollient feel. It would also probably be cheaper than using waxes and oils. This is a super common formula/base for deo sticks.

    You should also be able to use water and PG for the same bar formulation, but I haven’t experimented to see what the ratio should be so it is stable and doesn’t “sweat”. PG is cheap so I’m not worried about using that only.

    Otherwise, like Perry mentioned, it would be best if you can share your full formula.
    After thinking about it I wanted to ask... do you think if I add a vegetable oil, would it saponify?? Should I added it at the end (cooling stage) mixed with the fragances??
  • add*
  • Bill_TogeBill_Toge Member, Professional Chemist
    lauryl glucoside is not an effective emulsifier, you'd be better off removing it
    also, an emulsion can't be W/O if it has a high HLB emulsifier in it; thermodynamics favours O/W by any means possible, and W/O only forms if there's no possible way for O/W to form, i.e. no high HLB emulsifier
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • Bill_Toge said:
    lauryl glucoside is not an effective emulsifier, you'd be better off removing it
    also, an emulsion can't be W/O if it has a high HLB emulsifier in it; thermodynamics favours O/W by any means possible, and W/O only forms if there's no possible way for O/W to form, i.e. no high HLB emulsifier
    My main emulsifier is sorbitan stearate which has a very low HLB, I added a little bit of lauryl glucoside because I noticed when I added the hot water, the mixture became very lumpy, and after I added a small % of LG it became smooth again, I imagined it worked bc the HLBs added together to match the overall required HLB value??? Im gonna try some samples again with no lauryl glucoside and maybe Ill use my food hand mixer to try and get smaller droplets...

    Is there an easy way to know how much water I should add? or should I just run tests and see
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