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Deodorant cream gel not emulsifying
Hi there,
I’m formulating a “natural-as-possible” roll-on deodorant. The active ingredients are magnesium hydroxide and zinc ricinoleate, which I’ve chosen because I’ve found them to be extremely effective at neutralizing body odor. I want the consistency to be a thin cream gel that dries quickly. My current formulation creates an off-white color but I am open to a clear formulation too.
Although magnesium hydroxide is now a popular ingredient in stick deodorants, I rarely see it in liquid formulations. I assume this is because it isn’t water soluble. It makes a nice homogeneous solution with oils but separates to an unsightly suspension when mixed with water-soluble ingredients. Any thoughts on remedying this? Alternatively, feel free to chime in if there’s anything else about my formulation that jumps out as being problematic!
My most recent formulation is as follows:
- 67% water
- 17.5% Caprylic/capric triglyceride (I intend to lower this significantly as it feels too oily)
- 5% hydrogenated PEG-40 castor oil
- 4.5% zinc ricinoleate
- 4.5% magnesium hydroxide
- 1% glycerin
- 0.5% xanthan gum
The final pH is around 6. I may use lactic acid to lower the pH to between 3.5-4.5, as I’ve read there is a camp of deodorant companies that seems to state this range as ideal. (As a side note, adding lactic acid to the final mixture seems to increase the viscosity just a bit.)
I believe I need to introduce additional emulsifiers. I’m trying to make sense of appropriate ones for this oil-in-water mixture and would appreciate any suggestions on this. Once I can find a consistency that I’m happy with, I intend to introduce preservatives, stabilizers, some essential oils, and a scent fixative. Just taking this one step at a time.
Some emulsifiers I’ve seen used in o/w deodorants formulated with zinc ricinoleate are:
- Ceteareth-20
- Sorbitan Stearate
- Glyceryl Stearate /SE
- Polysorbate 20
Some emulsifiers I’ve seen used in o/w deodorants formulated with magnesium hydroxide are:
- Glyceryl Monostearate
- Polysorbate 80
For reference, this is the only gel formulation I’ve seen commercially available that uses magnesium hydroxide and I’m going for a similar texture: Asystem’s gel roll-on
Thanks all for your feedback!
Ash
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4 Replies
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You will need a low HLB and high HLB emulsifier to emulsify that oil. You currently only have a high HLB emulsifier. You could try adding glyceryl monostearate. Or start looking for emulsifiers blends that are suitable for use with high levels of electrolytes.I would recommend just starting with water, caprylic/capric triglycerides, glycerin, preservative and your emulsifiers. After you have formed a stable emulsion start adding in your active ingredients one a time to see what effect (if any) they have on your emulsion. -
I have to think MgOH2 is not as effective an odor-neutralizer as any zinc salt; I love the stuff in my antacid though, really zaps the acid reflux. How about nixing the Mg and subbing with zinc citrate? “Double Zinc Deodorant Stick”? This will work better and then you have all water-solubles. Jus sayin’
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@ozgirl - Thank you for your comment! It’s really helping to steer me in the right direction
After researching a little further today- do you know of any resources that can help me determine/calculate the best overall HLB for my mixture (and thereby calculate the respective ratios to include of each emulsifier?) Or should I determine this more experimentally (i.e. just generally aim for a higher HLB of the mixed emulsifiers because I’m creating an o/w mixture?)
Again, I appreciate yours or anyone else’s insights!
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@chemicalmatt - That’s an interesting idea. I know zinc citrate’s in some reputable, new, “natural” deodorants out there. I might have to experiment with it a bit, but could be a great alternative. Thanks for your message!
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